Journal of
Sensor and
Actuator Networks
Article
Design, Fabrication, and Testing of an Internet
Connected Intravenous Drip Monitoring Device
Pranshul Sardana 1, *, Mohit Kalra 2 and Amit Sardana 3
1
2
3
*
Department of Microsystems Engineering—IMTEK, University of Freiburg, 79110 Freiburg, Germany
Department of Informatik (INFOTECH), University of Stuttgart, 70569 Stuttgart, Germany;
mk.kalra94@gmail.com
Amazon Web Services, Dublin 18, Ireland; amitasricky@gmail.com
Correspondence: PRANSHULSARDANA@rediffmail.com
Received: 21 November 2018; Accepted: 27 December 2018; Published: 28 December 2018
Abstract: This paper proposes a monitoring system retro-fittable for existing Intravenous (IV) infusion
setup. Traditionally, doctors and nurses use their experience to estimate the time required by an IV
bottle to empty which makes the IV therapy vulnerable to human error. The current study proposes
an internet connected monitoring platform for IV drip chambers. The device enables doctors and
nursing staff to monitor the drip parameters wirelessly while emphasizing on low costs and high
degree of reliability. It has two main units, namely chamber unit and pole unit. Chamber unit
houses two types of sensors, optical based for drop detection and capacitive based for level detection,
both of which are placed on the chamber unit. The pole unit majorly consists of a microcontroller
and a GSM-based (Global System Mobile Communication) communication module. In addition,
the device was tested along with various parameters like accuracy, readout stability, change in fluid
used, changes in ambient conditions, end chamber conditions, optical unit malfunctions. Finally,
the monitored data was securely and reliably transmitted to commercial cloud service using HTTP
API calls (Hyper Text Transfer Protocol) (Application Programming Interface). This data was stored
and visualized for ease of readability for nurses and doctors.
Keywords: intravenous therapy; medical information systems; multi-sensor platform; chamber based
Monitoring; internet of medical things
1. Introduction
Intravenous therapy is a process of administering medicine into the body directly through the
veins. It is the fastest way of delivering fluids and medications throughout the body as it utilizes
the effective cardiovascular channel and its natural pumping forces. The working principle of IV is
that a bottle filled with the desired fluid medication is hung at a level higher than the patient’s body
to provide the fluid with a pressure, generated by gravitational potential energy, to overcome the
cardiovascular pressure.
IV therapy is an easy and effective procedure which allows a drop by drop administration of
medication. The process also has some innate limitations, like formation of tissue in the needle, rolling
of patient on the tube or over the hand, can block the flow of the fluid and compromises with the
patient’s life in severe scenarios. The major bottleneck of the process is monitoring the medicine bottle.
This is necessary so that the doctor or the nurse can know when to change the bottle. In general,
the bottle is changed when it is completely empty. The time it takes to empty is variable and depends
on parameters such as medicine quantity used, changes in back-pressure due to systolic-diastolic and
non-quantifiable dilation or contractions of veins.
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Because of the dynamic nature of the process, measurement based robust monitoring is necessary.
Failure of this can lead to various medical complications like backflow of blood into the IV setup.
In severe cases, if the bottle gets empty and it is not monitored for some time, it can also cause insertion
of air embolism [1,2] in the IV tube, which can be deadly and hence critical monitoring is required.
Currently, this monitoring is done by the nurses and/or by the patient’s attendant and in countries like
India, they have a poor nurse to patient ratio [3,4]. Over the last two decades, researchers have explored
various medical devices which can be connected to the Internet [5–9] which is giving rise to the Internet
of Medical Things (IoMT). These publications include devices like wearable sensors, middleware
platforms to connect the patient with the doctor using these wearable sensors and provides privacy
challenges linked with using healthcare information systems. An interesting use case of internet
connected medical devices is presented in [5], where an multiparameter monitoring wrist watch is
discussed. Whereas, [9] presents a mechanism for visualization, monitoring, and notification by a
middleware and hence shows the various sensors can be used together with software platform to
provide a more involving user experience.
Over the past two decades, many researchers have explored numerous techniques for sensing
the IV drip levels. One common aim of all the researchers was to develop a sensor system which
was not in contact with the IV fluid. The initial works were focused on developing low cost and
low energy consuming devices. The modern approaches are more inclined towards integrating new
alerts and monitoring platforms. However, some of these integrations were platform dependent and
hence limits the usability. Table 1 mentions some of the approaches, along with their advantages
and disadvantages.
Infrared detection is the most widely explored methods for drop detection and drip chamber being
the most widely accepted location of sensor placement. For these kinds of systems, the performance of
the device can be affected by ambient levels. Researchers have used various methods for reducing
ambient light. This is either done by software, i.e., by using moving average filters, or by providing
some physical barriers to reduce the effect. The second most common measurement parameter was
level detection.
The current work deals with design, fabrication and testing of an internet connected IV drip
monitoring device, which is capable of precisely monitoring drip rate, chamber liquid level alongside
detecting malfunctions in the measurement system. In the device, consideration is taken towards
having physical and electrical isolation between the sensor and IV fluid which is achieved by placing
the conducting plates between the drip chamber and chamber unit of the device, which makes the
device retrofit and free from the type of fluid used. The device is made robust against changes in IV
drip used and droplets on sidewalls by using a calibration button. Detailed design specifications are
discussed in the following section. In addition to design aspect, the work focuses on the testing of the
device in hospital environment for reliability. Apart from normal operations, cases like end chamber
conditions and LED pair malfunctions were tested rigorously with different ambient conditions to
prove robustness of the device. Detailed experiments and results are discussed in the later section.
J. Sens. Actuator Netw. 2019, 8, 2
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Table 1. Summary of Intravenous (IV) drip monitoring techniques, with their advantages
and disadvantages.
Year
2001
2002
2007
2009
2010
2011
Sensing Method (Location)
Infrared detection
(Drip chamber) [10]
Infrared detection
(Drip chamber) [11]
Infrared detection
(Drip chamber) [12]
Infrared detection
(Drip chamber) [13]
Infrared detection
(Drip chamber) [14]
Infrared detection
(Drip chamber) [15]
Advantages
Minimalistic approach to design
the circuit
Circuit consumes low power
Three IR pairs at different planes
Prismatic effect compensation
Efficient battery life
Uses wireless sensor networks
Multi-parameter measurement
Low energy consumption
Multi-layer software structure
Infrared region of operation
Disadvantages
Display consumes high power
No results provided
Unconnected system
No alarms generated
Non-consistent monitoring
Lack of testing
No device or design shown
No results provided
Listening periods reduces the accuracy
of the device
Display consumes high power
Lack of testing
2011
Flexible capacitive sensor
(Bottom of the bottle) [16]
Over the bottle setup
Low cost, Simple structure &
Compact
Binary value for the liquid level
Use of consumable, i.e., glue spray
2012
Microwave time-domain
reflectometry
(Bottle) [17]
Non-invasive sensing
Easy, low-cost fabrication, and
dimension control
Careful alignment between bottle and
holder is must
Dependent on the shape of bottle
Difficult to reproduce results
2013
Ray path simulations
(Drip chamber) [18]
Optical detection
Simulations
2015
Infrared detection
(Drip chamber) [19]
2015
Infrared detection
(Drip chamber) [20]
Centralized receiver module
Audio and visual alerts
2016
Infrared detection
(Drip chamber) [21]
PC and Android based monitoring
Multi-bag setup
2016
Infrared detection
(Drip chamber) [22]
Stakeholders interviewed
2017
Capacitive Level
detection [23]
Multi-parameter measurement
2017
Load cell
(Glucose hanger) [24]
Weight-based measurement
2017
Pressure sensing (Bottle) [25]
Circuit consumes low power
2018
Infrared sensor
(Drip chamber) [26]
Cloud-connected device
Testing done for ambient
environment
2018
Infrared sensor
(Drip chamber) [27]
Power supply backup
2018
Infrared sensor
(Drip chamber) [28]
Multi-alert system
2018
Infrared Detection
(Drip chamber) [29]
Device tested extensively in
different ambient conditions
Lack of testing results provided
Comparison with other
devices/schemes difficult
Incomplete, ineffective and costly
device
Lack of testing
Specific liquid amount can be used
Unknown sensor mounting
No device or design shown
Unconnected system
No results provided
Lack of testing
No device or design shown
Unknown sensor mounting
Restricted to one fluid type
No device or design shown
No alarms generated
Lack of testing
No device or design shown
Assumption about droplet volume
No results
No device or design shown
Lack of electrical isolation and safety
details and reliability
Display consumes high power
Unknown sensor mounting
Lack of testing
No actual device shown
Restricted to diameter of infusion tube
2. Materials and Methods
2.1. Working Principle
The two types of sensing were done by using two different sensors both of which were placed on
the chamber of the IV setup. Firstly, for detecting the number of drops, two infrared emitter-detector
pairs were used. And secondly, for detecting the chamber liquid level a pair of curved copper plates
J. Sens. Actuator Netw. 2019, 8, 2
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were fabricated to have capacitive level sensing. A detailed explanation of both types of sensors is
given below.
Drop detection is an essential component of an IV drip system. By detecting the number of drops
per minute, the drip rate can be calculated. This rate gives an estimation of the amount of medication
entering the patient’s body per minute. Caution should be taken here as to calculate the actual amount
of medication, volume per drop should be known. As the veins exert a variable amount pressure
during the systolic and diastolic periods, a precise measurement of medication amount cannot be
known. Hence, advance strategies are needed for monitoring the end conditions precisely.
2.2. Design and Fabrication
The optical sensor system comprises of two identical pairs of Infrared (IR) Transmitter (Tx )
(OSRAM SFH 4554) and Receiver (Rx ) (OSRAM SFH 203). Tx , Rx are matched to operate at IR of
850 nm wavelength and has a illumination diameter of 5 mm. Value of Rx is read through Analog to
Digital Converter (ADC) of Arduino which has a response time of 100 µs [30]. For capacitive sensor
system, the plates of the capacitor were fabricated in dimensions of 24 mm × 29 mm, in accordance
with the circumference and height of the drip chamber with 300 µm thickness and press-fitted in the
inner layer of the chamber mount. The capacitance value was measured using a CM-1500 digital
capacitance meter. This value was measured to be 11 pF.
PCB housing the signal conditioning circuitry for optical and capacitive sensor system were
designed on Proteus 8.1. Dimensions of PCB housing the IR LED and the circuit for capacitancefrequency conversion is 34 mm × 15 mm. The dimensions of IR PCB are 15 mm × 19 mm. Manual
routing was done while PCB designing with minimum track width kept at 15 mils for signal carrying
track and maximum at 50 mils for the power track. LM555 IC (PDIP packaging, manufactured by Texas
Instruments) is used in the capacitance-frequency conversion circuit. Effect of parasitic capacitance
was minimized by routing the connection wires of capacitor by the shortest path along the hinge and
through hole in the chamber mount. The setup minimizes the stray capacitance and still provides an
easy way of fabrication. The formed measurement unit provides a point to point measurement of the
fluid inside the chamber.
Figure 1 shows the schematic and layout of IR, 555 PCBs. The IR PCB contains receiver
IR photodiodes and limiting resistors with pin connectors for the diodes. 555 PCB contains the
transmission LEDs and 555 circuit as an astable multi-vibrator to convert the observed capacitance
into frequency. The frequency signal was then fed to the micro-controller for processing. Equation (1)
describes the capacitance to frequency formula as follows:
f =
1
1.44
=
T
( R1 + 2R2 ).C
(1)
where R1 (1 kΩ) is the resistance between VCC and Discharge pin, and R2 (1 MΩ) is the resistance
between Discharge pin and Trigger pin (connected with Threshold pin). Here, C is the value of
capacitance which is formed due to the copper plates placed on the inner curved surface of the
chamber housing. For a parallel plate capacitor, the value of C depends on the following factors as
described in Equation (2).
A
C = ε 0 .ε r .
(2)
d
where ε0 is the absolute permittivity of free space, which is equal to 8.85 × 10−12 F/m and εr is the
relative permittivity of the dielectric material in between the plates (in our case, Air for Empty Chamber
and Intravenous fluid being administered for the full chamber conditions). A is the surface area of the
dielectric plates and d is the distance between the plates. In this case, this formula is not used strictly
since the plates are curved and hence are not truly parallel as the distance near the edges (on curved
surface) is less than measured from the center of the plate. Moreover, the value of relative permittivity
is material depended, since our aim is to develop a system which can be used for all types of fluids
J. Sens. Actuator Netw. 2018, 7, x FOR PEER REVIEW
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sensor
J. Sens.The
Actuator
Netw. casing
2019, 8, 2 was
designed to optimize the working and ease of use. It was curved
5 of 20
internally with a radius of 8.25 mm to fit the chamber. The outer end of both pieces of the casing was
designed to hold the PCBs. The casing with 555 PCB had a hole in it to minimize the wire length as
being
administered.
Hence,
rather
calculating
value
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the frequency
Computer-Aided
Design
J. Sens. Actuator Netw. 2018, 7, x FOR PEER REVIEW
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The sensor casing was designed to optimize the working and ease of use. It was curved
internally with a radius of 8.25 mm to fit the chamber. The outer end of both pieces of the casing was
designed to hold the PCBs. The casing with 555 PCB had a hole in it to minimize the wire length as
described earlier. The upper part of both the casings had two holes each of radii 3 mm to fit the IR
LEDs and photodiodes. The holes were placed on a height below the hanging drop length to ensure
that the observed drop is certainly falling. Also, using two pairs of sensors instead of one enhances
the line of sight by approximately 80% and hence ensures a reliable functioning of the system, a
reduction in intensity of light in any one of the pairs will signify crossing of a drop. Figure 2 shows
the Computer-Aided Design of sensor casing.
Figure 1.
1. Schematic
Schematic and
and layout
layout of
of (a)
(a) Infrared
Infrared (IR);
(IR); (b)
(b) 555
555PCBs.
PCBs.
Figure
The sensor casing was designed to optimize the working and ease of use. It was curved internally
with a radius of 8.25 mm to fit the chamber. The outer end of both pieces of the casing was designed to
hold the PCBs. The casing with 555 PCB had a hole in it to minimize the wire length as described earlier.
The upper part of both the casings had two holes each of radii 3 mm to fit the IR LEDs and photodiodes.
The holes were placed on a height below the hanging drop length to ensure that the observed drop
is certainly falling. Also, using two pairs of sensors instead of one enhances the line of sight by
approximately 80% and hence ensures a reliable functioning of the system, a reduction in intensity
of light in any one of the pairs will signify crossing of a drop. Figure 2 shows the Computer-Aided
Design of sensor casing.
Figure 1. Schematic and layout of (a) Infrared (IR); (b) 555 PCBs.
Figure 2. Designs of the sensor casings: (a) isometric view and (b) top view.
Another major part of the device was a box placed at the IV drip stand. It was made from a 3
mm thick acrylic sheet. It was designed in SolidWorks and fabricated using a laser cutter. The box
was big enough (300 mm × 360 mm) to house microcontroller and communication unit.
Furthermore, it had enough space to let the IV standpipe and square acrylic pipe through it.
Through holes were made in the box for passing these pipes. This design allowed the device to be
adjusted in two axes, giving it more freedom and ease the operability.
Box houses two buttons. The power button is used to turn the device on and off when required.
The calibration button calibrates the device according to the current conditions when it starts. This
allows the user Figure
to use 2.
IVDesigns
drips with
material
and
optical
properties
without
of thedifferent
sensor casings:
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and (b) top
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isometric
the functionality of the device. An additional stopper was used below the box to hold it at the
Another
major
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The calibration button calibrates the device according to the current conditions when it starts.
starts. This
allows the user to use IV drips with different material and optical properties without compromising
the functionality of the device. An additional stopper was used below the box to hold it at the
desired height. Figure 3 shows (a) the device in a hospital setting and (b) positioning of various
sensors incorporated in the sensing unit.
J. Sens. Actuator Netw. 2019, 8, 2
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allows the user to use IV drips with different material and optical properties without compromising
the functionality of the device. An additional stopper was used below the box to hold it at the desired
height. Figure 3 shows (a) the device in a hospital setting and (b) positioning of various sensors
incorporated
the 2018,
sensing
unit.
J. Sens. Actuatorin
Netw.
7, x FOR
PEER REVIEW
6 of 19
Figure
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(300~600
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the algorithm,
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the values
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(1/2.1)
476 Hz, which
more than
20×which
faster is
than
thethan
usual
drip
ratethan
(2 drops
per
after 2.1 rate
ms, is
thus
our sampling
rate isis(1/2.1)
476 Hz,
more
20×
faster
the usual
second).
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communication
module
used
is
SIM900
GSM
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Shanghai,
drip rate (2 drops per second). The communication module used is SIM900 GSM (SIMCom Wireless
China)
whichShanghai,
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MHz850/900/1800/1900
with GSM (2G) network.
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devicescan
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setupand
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eachdevice,
device,multiple
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nodes
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fordifferent
different
parameters.This
Thisenables
enableseasy
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monitoringofofmultiple
multipleIVIVapparatus
apparatusatatthe
the
same time. In our device three nodes were created, each for one parameter: volume left in the
chamber, IR used and drip rate.
For analysis in the cloud, Rules perform checks on critical parameters to be monitored. For
testing and validation, three rules were created. The volume rule was made to fire when volume left
in chamber drops below 80% of the full chamber level. Secondly, LED detection rule fires when both
J. Sens. Actuator Netw. 2019, 8, 2
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same time. In our device three nodes were created, each for one parameter: volume left in the chamber,
IR used and drip rate.
For analysis in the cloud, Rules perform checks on critical parameters to be monitored. For testing
and validation, three rules were created. The volume rule was made to fire when volume left in
J.
Sens. Actuator
Netw.
2018, 7,80%
x FOR
REVIEW
of 19
chamber
drops
below
ofPEER
the full
chamber level. Secondly, LED detection rule fires when7 both
LEDs are not used for a drop detection. Thirdly, the drip rate rule fires when the drip rate is higher than
function,
which
triggered
whenwith
a rule
firesalarms
(violated).
There
are various
possibilities
alarms
150
or lower
thanare
5. In
conjunction
rules,
are used
to perform
a specific
task orof
function,
which are
cantriggered
be used such
sending
email toThere
a specified
address,
SMS or phone
callwhich
to a mobile
which
whenas
a rule
fires an
(violated).
are various
possibilities
of alarms
can be
number.
used such as sending an email to a specified address, SMS or phone call to a mobile number.
Previously,
there have
have been
been internet-based
internet-based patient
patient remote
remote monitoring
monitoring solutions
solutions [31],
[31], but
but in
in such
Previously, there
such
solutions,
there
was
a
dependency
on
the
platform
such
as
Linux,
Windows,
Android
[32],
iOS
solutions, there was a dependency on the platform such as Linux, Windows, Android [32], iOS which
which
ran
the
application
GUI.
Limitation
of
such
solution
is
the
development
time
and
costs
which
ran the application GUI. Limitation of such solution is the development time and costs which are
are
incurred
to their
diverse
running
environment.
However,
a cloud-based
solution,
incurred
duedue
to their
diverse
running
environment.
However,
withwith
a cloud-based
solution,
the the
OS
OS
dependency
is
removed.
This
enables
any
device
with
a
web
browser
to
have
the
monitoring
dependency is removed. This enables any device with a web browser to have the monitoring GUI,
GUI,
increasing
observability
detect
any abnormality
real
time.
report
UI is user
increasing
observability
to detecttoany
abnormality
in real time.inThe
report
UI The
is user
configurable
and
configurable
and
can
be
customized
as
per
the
requirement
of
the
hospital.
can be customized as per the requirement of the hospital.
2.3.
2.3. Algorithm
Algorithm Description
Description and
and Cloud
Cloud
2.3.1. Setup Loop
In setup loop, the hardware and software baud rates, the pins for IR LEDs, the calibration state
LED (include the third LED everywhere) and the buzzer was defined as the output. No power was
channeled through any of the output pins. Figure 4 show the block diagram of setup
setup loop.
loop.
Figure 4.
Block diagram
diagram of
of setup
setup loop.
loop.
Figure
4. Block
2.3.2. Main Loop
2.3.2. Main Loop
In the main loop, the push state of calibration button was checked. The procedure for calibrating
In the main loop, the push state of calibration button was checked. The procedure for
the device is as follows, when the chamber is empty, the calibration button is pushed once, the dielectric
calibrating the device is as follows, when the chamber is empty, the calibration button is pushed
material between the capacitive plates is air, hence the value of frequency (dependent on the capacitance
once, the dielectric material between the capacitive plates is air, hence the value of frequency
value C) is calculated according to Equation (1), the device calibrates according to the optical properties
(dependent on the capacitance value C) is calculated according to Equation (1), the device calibrates
of the empty chamber used and the calibration LED starts blinking. Now, the chamber casing can be
according to the optical properties of the empty chamber used and the calibration LED starts
removed and placed back after filling with the IV fluid. Next, the calibration button is pushed again,
blinking. Now, the chamber casing can be removed and placed back after filling with the IV fluid.
and the device configures the full chamber frequency depending upon the dielectric property of the
Next, the calibration button is pushed again, and the device configures the full chamber frequency
depending upon the dielectric property of the liquid used. It is followed by a digital filtering which
removes any noise. Figure 5a shows the block diagram of the main loop.
In calibration block, the ‘read IR’ subroutine is used to calculate the optical intensity observed
by the IR detectors in empty chamber configuration which is used to define thresholds for the
ongoing operation. This was done for both the pairs individually and the total number of drops were
initialized as null. For calibrating the capacitive sensor, high and low times of the pulse coming from
achieved calibration time is less 50 µs. Also, an LED indicates when calibration is in progress. Figure
5b shows the block diagram of the calibration block.
After complete calibration, the calibration LED starts blinking to indicate the mode to the user.
At next push, the device calibrates itself according to the full chamber condition and LED glows
J. Sens. Actuator Netw. 2019, 8, 2
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continuously indicating operating mode. The frequency obtained now is the full chamber frequency
(FCF). A similar averaging was also used here to reduce noises. Finally, the device enters another
repetitive
for sensing,
analyzing
transmitting
functionalities.
5c shows
the
liquid
used.subroutine
It is followed
by a digital
filteringand
which
removes any
noise. FigureFigure
5a shows
the block
block diagram
of operate
diagram
of the main
loop. block of the main loop.
Figure
Figure5.5. Block
Block diagram
diagram of:
of: (a)
(a) main
main loop;
loop; (b)
(b) calibration
calibration block;
block; and
and(c)
(c)operate
operateblock
blockof
ofmain
mainloop.
loop.
calibration
block, the
‘readTermination
IR’ subroutine is used to calculate the optical intensity observed by
2.3.3.InGSM
Initialization
& GSM
the IR detectors in empty chamber configuration which is used to define thresholds for the ongoing
This function
usedfortoboth
initialize
the individually
GSM module.
It is
device
specific
in initialized
which the
operation.
This wasisdone
the pairs
and
thea total
number
of function,
drops were
initialization
function
is
called
to
check
if
the
module
has
been
successfully
initialized
and
as null. For calibrating the capacitive sensor, high and low times of the pulse coming from
thea
connection
has
been
made.
GSM
Termination
subroutine
is
used
to
terminate
the
GSM
connection.
555 outputs were used to obtain the total pulse time and hence empty chamber frequency (ECF) was
obtained. Here, averaging of multiple ECFs were used to reduce the amount of noise. The achieved
2.3.4. HTTP Initialization
calibration time is less 50 µs. Also, an LED indicates when calibration is in progress. Figure 5b shows
the block
calibration
block.
Thisdiagram
functionof
is the
used
to establish
HTTP connection with the server where data logging is being
done.
Once
established,
it allows
data collected
at the
device to
to indicate
be transmitted
following
the
After
complete
calibration,
thethe
calibration
LED starts
blinking
the mode
to the user.
HTTP
These
parameters
establishing
thetoconnection
and posting
data to
theLED
cloud
have
At
nextprotocol.
push, the
device
calibratesfor
itself
according
the full chamber
condition
and
glows
been provided
by the cloud
provider
[33].The
Figure
6 shows
the block
diagram
of HTTP
initialization.
continuously
indicating
operating
mode.
frequency
obtained
now
is the full
chamber
frequency
(FCF). A similar averaging was also used here to reduce noises. Finally, the device enters another
repetitive subroutine for sensing, analyzing and transmitting functionalities. Figure 5c shows the block
diagram of operate block of the main loop.
J. Sens. Actuator Netw. 2019, 8, 2
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2.3.3. GSM Initialization & GSM Termination
This function is used to initialize the GSM module. It is a device specific function, in which the
initialization function is called to check if the module has been successfully initialized and a connection
has been made. GSM Termination subroutine is used to terminate the GSM connection.
2.3.4. HTTP Initialization
This function is used to establish HTTP connection with the server where data logging is being
done. Once established, it allows the data collected at the device to be transmitted following the HTTP
protocol. These parameters for establishing the connection and posting data to the cloud have been
J. Sens. Actuator Netw. 2018, 7, x FOR PEER REVIEW
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provided
by the
provider
[33].
Figure 6 shows the block diagram of HTTP initialization. 9 of 19
Figure
Protocol (HTTP)
(HTTP) initialization.
Figure 6.
6. Block
Block diagram
diagram of
of Hyper
Hyper Text
Text Transfer
Transfer Protocol
Figure
6.
Block
diagram
of
Hyper
Text
Transfer
Protocol (HTTP) initialization.
initialization.
2.3.5. Post Data
2.3.5. Post Data
In this function, a string of data is formed containing all the relevant information, such as the
In this function, a string of data is formed containing all the relevant information, such as the
device key, drip rate, volume left in the chamber, etc., which is to be
be transmitted
transmitted to the cloud. After
device key, drip rate, volume left in the chamber, etc., which is to be transmitted to the cloud. After
formation of this string of data, suffixes were added, and the data is posted using cloud defined
formation of this string of data, suffixes were added, and the data is posted using cloud defined
functions. Figure 7 shows the block diagram of HTTP post.
functions. Figure 7 shows the block diagram of HTTP post.
Figure 7.
7. Block
Block diagram
diagram of
of HTTP
HTTP post.
post.
Figure
Figure 7. Block diagram of HTTP post.
2.3.6. Drop Count
2.3.6. Drop Count
This function is used to detect the falling drop and increment the drop count value. For each
This function is used to detect the falling drop and increment the drop count value. For each
LED pair a reading function is called consecutively, to observe fluctuations in observed intensity.
LED pair a reading function is called consecutively, to observe fluctuations in observed intensity.
When a drop passes either partially or fully through the line of sight of any of the diode pairs, a
When a drop passes either partially or fully through the line of sight of any of the diode pairs, a
reduction in intensity at the receiver end occurs and thus a drop is detected.
reduction in intensity at the receiver end occurs and thus a drop is detected.
The drop detection is done via a two-step threshold process. In the first step, an intensity-based
The drop detection is done via a two-step threshold process. In the first step, an intensity-based
J. Sens. Actuator Netw. 2019, 8, 2
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2.3.6. Drop Count
This function is used to detect the falling drop and increment the drop count value. For each LED
pair a reading function is called consecutively, to observe fluctuations in observed intensity. When a
drop passes either partially or fully through the line of sight of any of the diode pairs, a reduction in
intensity at the receiver end occurs and thus a drop is detected.
The drop detection is done via a two-step threshold process. In the first step, an intensity-based
threshold is done. The fall in the IR intensities for both receiver pairs is matched with their respective
thresholds. If either pair records a drop below the threshold, the percentage of drop in intensity of
both the pairs is calculated. In the second step, if both pairs are working and register new intensity
being less than the threshold intensity, it is recorded as drop detected, else the situation is ignored.
Measurement of IR intensity is a multi-step process, optimized to run in 3 ms. Here first, the
respective
IR Netw.
LED2018,
of the
turned
off and ambient measurement is done. This value is read10using
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ADC and stored to a temporary variable for later comparison. Next, IR LED is turned on and value of
value of photodiode
is read.
This
wholeisprocess
is repeated
till thenumber
desiredofnumber
ofare
samples
are
photodiode
is read. This
whole
process
repeated
till the desired
samples
obtained.
obtained.
average
value is Figure
returned.
Figure
8 shows
the blockofdiagram
of drop count.
Finally, anFinally,
averagean
value
is returned.
8 shows
the
block diagram
drop count.
Figure 8.
8. Block
Block diagram
diagram of
of drop
drop count.
count.
Figure
2.3.7. Critical Level using IIR Filtering
2.3.7. Critical Level using IIR Filtering
This function calculates the level of liquid left in the chamber. Due to change in liquid levels,
This function calculates the level of liquid left in the chamber. Due to change in liquid levels, the
the dielectric coefficient of the capacitor changes, this change in capacitance affects the charging/
dielectric coefficient of the capacitor changes, this change in capacitance affects the
discharging time of the capacitor and hence the frequency of 555 circuit changes. The frequency in the
charging/discharging time of the capacitor and hence the frequency of 555 circuit changes. The
setup varies from about 65 KHz (Empty Chamber Frequency, (ECF)) for a completely empty chamber to
frequency in the setup varies from about 65 KHz (Empty Chamber Frequency, (ECF)) for a
40 KHz (Full Chamber Frequency (FCF)) when the chamber is filled to half of its height (29 mm) for D5
completely empty chamber to 40 KHz (Full Chamber Frequency (FCF)) when the chamber is filled to
liquid, hence making the measurement system extremely sensitive (about 850 Hz/mm). The chamber
half of its height (29 mm) for D5 liquid, hence making the measurement system extremely sensitive
is required to be filled only to half of its height because if it is filled more than that the droplets will not
(about 850 Hz/mm). The chamber is required to be filled only to half of its height because if it is filled
have enough height to fall and the drip will not perform properly. This high sensitivity also detects
more than that the droplets will not have enough height to fall and the drip will not perform
fluctuations produced because of ripples. For smoothing out the frequency response and for estimating
properly. This high sensitivity also detects fluctuations produced because of ripples. For smoothing
the liquid level with respect to full chamber level, infinite impulse response (IIR) filtering was used.
out the frequency response and for estimating the liquid level with respect to full chamber level,
Figure 9 shows block diagram of critical level loop.
infinite impulse response (IIR) filtering was used. Figure 9 shows block diagram of critical level loop.
half of its height (29 mm) for D5 liquid, hence making the measurement system extremely sensitive
(about 850 Hz/mm). The chamber is required to be filled only to half of its height because if it is filled
more than that the droplets will not have enough height to fall and the drip will not perform
properly. This high sensitivity also detects fluctuations produced because of ripples. For smoothing
out
the frequency response and for estimating the liquid level with respect to full chamber 11level,
J. Sens. Actuator Netw. 2019, 8, 2
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infinite impulse response (IIR) filtering was used. Figure 9 shows block diagram of critical level loop.
J. Sens. Actuator Netw. 2018, 7, x FOR PEER REVIEW
Figure 9.
9. Block
Block diagram
diagram of
of critical
critical level
level loop.
loop.
Figure
11 of 19
2.3.8. Spend Time
This function was used as a replacement for delays in GSM initialization and post data
subroutines. The
time.
Doing
this
results
in
Thefunction
functionexecutes
executesmonitoring
monitoringsubroutines
subroutinesfor
fora aspecified
specified
time.
Doing
this
results
efficient
utilization
of of
resources
in efficient
utilization
resourcesalongside
alongsideensuring
ensuringthat
thatcritical
criticalparameters
parameterssuch
such as
as chamber level
are continuously monitored and no drop crossing the IR sensor pair is missed, thereby, increasing
efficiency and reliability of the device.
device. Figure 10 shows the block
block diagram
diagram of
of spend
spend time
time loop.
loop.
Figure 10.
10. Block
Block diagram
diagram of
of spend
spend time
time loop.
loop.
Figure
2.3.9. Green Blink and Timed Green Blink
2.3.9. Green Blink and Timed Green Blink
These subroutines tell the user if the device is in the calibration mode or not via the calibration
These subroutines tell the user if the device is in the calibration mode or not via the calibration
LED. The green blink fragment alternatively makes the calibration LED high and low. The alternation
LED. The green blink fragment alternatively makes the calibration LED high and low. The
is executed along with ‘timed push read’ subroutine so that no button push is missed. The timed
alternation is executed along with ‘timed push read’ subroutine so that no button push is missed.
green blink subroutine is a way of calling the green blink subroutine for a fixed time. This was also an
The timed green blink subroutine is a way of calling the green blink subroutine for a fixed time. This
alternative to delays and added more functionality to the device. Figure 11 shows the block diagram
was also an alternative to delays and added more functionality to the device. Figure 11 shows the
of (a) green blink; (b) timed green blink blocks.
block diagram of (a) green blink; (b) timed green blink blocks.
These subroutines tell the user if the device is in the calibration mode or not via the calibration
LED. The green blink fragment alternatively makes the calibration LED high and low. The
alternation is executed along with ‘timed push read’ subroutine so that no button push is missed.
The timed green blink subroutine is a way of calling the green blink subroutine for a fixed time. This
was also an alternative to delays and added more functionality to the device. Figure 11 shows
the
J. Sens. Actuator Netw. 2019, 8, 2
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block diagram of (a) green blink; (b) timed green blink blocks.
Figure
Figure11.
11.Block
Blockdiagram
diagramof:
of: (a)
(a) green
greenblink
blinkand
and(b)
(b)timed
timedgreen
greenblink
blinkblocks.
blocks.
2.3.10. Push Read and Timed Push Read
2.3.10. Push Read and Timed Push Read
The function makes use of push read as its subroutine. The uses of both are described as follows.
The function makes use of push read as its subroutine. The uses of both are described as
The function push read ensures that the digital input which is read at a pin is read only once for each
follows. The function push read ensures that the digital input which is read at a pin is read only once
switch press.
for each switch press.
mechanical
switches,
push
button press can cause voltage fluctuations. To avoid reading
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In mechanical
switches,
a push
button press can cause voltage fluctuations. To avoid reading
these fluctuating or any stray voltages as pushes, a de-bounce delay was used. Here, the pulse must
these fluctuating or any stray voltages as pushes, a de-bounce delay was used. Here, the pulse must
stay
of of
at at
least
50 ms
to read
it asita as
high.
Timed
push push
read function
takes
stay as
ashigh
highstate
statefor
forsettling
settlingtime
time
least
50 ms
to read
a high.
Timed
read function
an
input
of spend
the time
allowed
push for
readpush
to run
through.
12
takes
an argument
input argument
of time,
spendwhich
time,iswhich
is the
time for
allowed
read
to runFigure
through.
shows
block diagram
(a) pushofread;
(b) timed
read push
blocks.
Figure the
12 shows
the blockofdiagram
(a) push
read;push
(b) timed
read blocks.
Figure
Figure 12.
12. Block
Block diagram
diagram of:
of: (a)
(a) push
push read
read and
and (b)
(b) timed
timed push
push read
read blocks.
blocks.
2.3.11. GSM Response and GSM Connection Check
2.3.11. GSM Response and GSM Connection Check
The former displays the response messages received from the GSM module. The latter is used to
The former displays the response messages received from the GSM module. The latter is used
check if the GSM connection is stable or not.
to check if the GSM connection is stable or not.
3. Results
All the following experiments were at least performed with Dextrose 5% in Water (D5W or D5).
D5 was chosen because it is one of the most common fluids involved in the general IV therapy.
Moreover, some experiments like ‘stability of level detection’ and ‘change in the liquid used’ were
J. Sens. Actuator Netw. 2019, 8, 2
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3. Results
All the following experiments were at least performed with Dextrose 5% in Water (D5W or D5).
D5 was chosen because it is one of the most common fluids involved in the general IV therapy.
Moreover, some experiments like ‘stability of level detection’ and ‘change in the liquid used’ were
performed with four different fluids, namely D5, Dextrose 25% in Water (D25), tap water, and packaged
drinking water. D25 is another common liquid used in IV therapy. This, along with two different
water samples, were selected because different IV fluids have somewhat different optical and material
properties but having water as a major component and hence system robustness on these liquids can
be tested. Furthermore, as the sensor unit uses optical principle for drop detection, it was crucial to test
the device for different ambient conditions, which was done for the test ‘change in ambient condition’.
All the other tests were performed in a regular indoor hospital scenario.
The LED used graphs show which LED transmitter-receiver pair (also mentioned simply as LED
pair) detected the falling drop. In the graphs below, numbers 1 and 2 shows that one of the two pairs
detected the falling drop. The pairs are named as left and right, respectively. Whereas, 3 shows that
both the pairs detected the falling drop simultaneously.
3.1. Accuracy of Drop Count
A manual drop count was performed to ensure that the device is counting each falling drop.
As
theActuator
drip chamber
covered
by the sensor casing, there is very limited space available
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for verification of the drop count by other mechanisms. Moreover, manual drop count is a standard
practice in
in the
the IV
IV therapy
therapy and hence, it can be efficiently
efficiently used
used as
as a cheap and robust
robust solution
solution for this
practice
verification. Further, it was
was also
also made
made sure
sure that
that every
every falling
falling drop
drop is
is counted
counted only
only once.
once. The
The device
device
verification.
was operated
operated25
25times
timeson
ondifferent
differentIVIVspeeds
speedswith
with
a manual
count
made
alongside.
A drop
count
of
was
a manual
count
made
alongside.
A drop
count
of 50
50
was
made
each
time
and
the
device
detected
each
count
without
any
error.
was made each time and the device detected each count without any error.
3.2. Stability of Level Detection
Stability of level detection is an important parameter to ensure that the readout
readout is
is stable
stable during
during
device operation. To do that four sets of readings were made with different fluids to ensure that
that the
the
readouts are not
not affected
affected by
by the
the fluid
fluid change.
change. The drips were operated at different speeds
speeds to ensure
ensure
that the readouts
readouts were also
also not
not affected
affected by
by drip
drip rate.
rate. The readouts were performed
performed for around 30 s
each.
each. Figure 13 shows the stability
stability of
of level
level detection
detection for
for D5
D5 and
and D25.
D25.
Figure
for (a)
(a) Dextrose
Dextrose 5%
5% in
in Water
Water (D5);
Figure 13.
13. Stability
Stability of
of level
level detection
detection for
(D5); (b)
(b) Dextrose
Dextrose 25%
25% in
in Water
Water
(D25).
(D25).
The
The readouts
readouts are
are quite
quite stable
stable with
with time.
time. If
If needed,
needed, the
the noise
noise associated
associated can
can be
be removed
removed using
using
software
filtering
or
parasitic
reduction.
As
the
level
detection
is
done
by
capacitive
setup,
readouts
software filtering or parasitic reduction. As the level detection is done by capacitivethesetup,
the
are
unaffected
by
ambient
IR.
readouts are unaffected by ambient IR.
3.3. Change in Fluid Used
3.3. Change in Fluid Used
Because of difference in optical properties of IV fluids, it was necessary to test the device on
Because of difference in optical properties of IV fluids, it was necessary to test the device on
different fluids as mentioned previously. The device should be able to detect the number drops
different fluids as mentioned previously. The device should be able to detect the number drops
accurately independent of the fluid used. D5 and D25 are also the two most transparent fluids used
in the IV therapy because the majority of their content is water. Testing on these fluids will ensure
that the device will perform more robustly on more opaque fluids like blood. Secondly, it was very
crucial to know that during the operation of the device using the above-mentioned fluids which pair
of LEDs were responsible to detect the falling drops. As the output of both the LEDs was logged
readouts are unaffected by ambient IR.
3.3. Change in Fluid Used
Because of difference in optical properties of IV fluids, it was necessary to test the device
on
J. Sens. Actuator Netw. 2019, 8, 2
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different fluids as mentioned previously. The device should be able to detect the number drops
accurately independent of the fluid used. D5 and D25 are also the two most transparent fluids used
accurately
independent
of the
used.ofD5
andcontent
D25 areisalso
the two
mostontransparent
fluids
in
in
the IV therapy
because
the fluid
majority
their
water.
Testing
these fluids
will used
ensure
the
IV
therapy
because
the
majority
of
their
content
is
water.
Testing
on
these
fluids
will
ensure
that
that the device will perform more robustly on more opaque fluids like blood. Secondly, it was very
the device
will perform
morethe
robustly
on more
blood. Secondly, itfluids
was very
crucial
crucial
to know
that during
operation
of theopaque
device fluids
using like
the above-mentioned
which
pair
to know
the operation
of the device
fluids
LEDs
of
LEDs that
wereduring
responsible
to detect
falling using
drops.the
Asabove-mentioned
the output of both
thewhich
LEDspair
wasoflogged
were
to detect the
falling
drops.
the output
of both the
LEDs
logged
onto responsible
separate controller
pins,
these
pinsAswere
consecutively
read
to was
know
the onto
LEDseparate
pair(s)
controller pins,
pins were
consecutively
to knowuse
the of
LED
pair(s)
for detection.
responsible
for these
detection.
Figure
14 shows theread
percentage
LED
pairsresponsible
with the different
fluid
Figure 14 shows the percentage use of LED pairs with the different fluid used.
used.
Figure 14.
14. Percentage
Percentage use
use of
of LED
LED pairs
pairs with
with different
different fluid
Figure
fluid used.
used.
In the
that only
only LED
LED pair
that only
only 22 was
In
the graph
graph above,
above, 11 shows
shows that
pair 11 was
was responsible,
responsible, 22 shows
shows that
was
responsible,
and
3
shows
that
both
the
led
pairs
for
that
particular
readout.
It
can
be
seen
that
in in
95%
J.
Sens.
Actuator
Netw.
2018,
7,
x
FOR
PEER
REVIEW
14
of of
19
responsible, and 3 shows that both the led pairs for that particular readout. It can be seen that
95%
detection
cases,
both
the
pairs
were
able
to
detect
a
falling
drop.
In
only
5%
of
cases
a
single
LED
pair
of detection cases, both the pairs were able to detect a falling drop. In only 5% of cases a single LED
pair detected
the falling
The lesser
sensitivity
the second
pair
be because
of reasons
various
detected
the falling
drop. drop.
The lesser
sensitivity
for thefor
second
pair may
be may
because
of various
reasons
like droplets
on walls
the side
walls
of the chamber.
These reduce
droplets
reduce
the of
intensity
of light
like
droplets
on the side
of the
chamber.
These droplets
the
intensity
light reaching
reaching
theand
detector
and hence
reduce theofsensitivity
of the pairtoifthe
compared
to Another
the other
pair.
the
detector
hence reduce
the sensitivity
the pair if compared
other pair.
reason
Another
reason
can
be
changed
in
ambient
condition
as
the
device
operates,
the
effect
of
which
is
can be changed in ambient condition as the device operates, the effect of which is studied in the next
studied Figure
in the next
section.
shows drop
the graph
and
LED used
the
section.
15 shows
theFigure
graph 15
between
countbetween
and LEDdrop
usedcount
for the
different
fluidfor
used.
different
fluid
used.
From
both
the
graphs
it
can
be
seen
that
the
failure
of
LED
pair
is
consistent
From both the graphs it can be seen that the failure of LED pair is consistent during one device setting
duringindicate
one device
setting
which
indicate
that the
failure might
be because
chamber
which
that the
failure
might
be because
of chamber
conditions
and willofbe
exploredconditions
in a later
and will
belong
explored
in a later
work with long term device testing.
work
with
term device
testing.
Figure
Figure 15.
15. Graph
Graph between
between drop
drop count
count and
and LED
LED used
used for
for different
different fluid
fluid used.
used.
3.4. Change in Ambient Conditions
3.4. Change in Ambient Conditions
Here, the influence of environmental conditions on device operation was observed. As the drop
Here, the influence of environmental conditions on device operation was observed. As the drop
detection mechanism was optical, stray IR illuminations can cause distortions in operation and can
detection mechanism was optical, stray IR illuminations can cause distortions in operation and can
cause drop detection to fail or give false results. However, change in ambient IR light does not cause
cause drop detection to fail or give false results. However, change in ambient IR light does not cause
major functional failures in the prototype since the algorithm has been designed to calibrate on the
major functional failures in the prototype since the algorithm has been designed to calibrate on the
go. To verify this, the experiment was performed in three different conditions, namely cloudy, home,
go. To verify this, the experiment was performed in three different conditions, namely cloudy, home,
and night, without changing the drip placement. It was important to ensure that there were no drops
and night, without changing the drip placement. It was important to ensure that there were no drops
on the drip chamber because these droplets can cause a lesser sensitivity of the sensor pairs. As the
on the drip chamber because these droplets can cause a lesser sensitivity of the sensor pairs. As the
chamber positioning was not changed, the device was unaffected by drip chamber variations and the
chamber positioning was not changed, the device was unaffected by drip chamber variations and
readouts were only sensitive to changes in ambient conditions.
the readouts were only sensitive to changes in ambient conditions.
Cloudy was a readout in an outdoor environment on a cloudy day where the changes in
ambient conditions are very frequent and severe as compared to a normal hospital condition.
Secondly, the home condition was a regular indoor hospital environment during the daytime.
Finally, the night was a condition in an indoor environment during night time, where ambient and
changes in it are significantly lesser than the other two conditions. In these three conditions, both the
cause drop detection to fail or give false results. However, change in ambient IR light does not cause
major functional failures in the prototype since the algorithm has been designed to calibrate on the
go. To verify this, the experiment was performed in three different conditions, namely cloudy, home,
and night, without changing the drip placement. It was important to ensure that there were no drops
on the drip chamber because these droplets can cause a lesser sensitivity of the sensor pairs. As the
J. Sens. Actuator Netw. 2019, 8, 2
15 of 20
chamber positioning was not changed, the device was unaffected by drip chamber variations
and
the readouts were only sensitive to changes in ambient conditions.
Cloudy was
wasa areadout
readout
in outdoor
an outdoor
environment
on a cloudy
day the
where
the changes
in
Cloudy
in an
environment
on a cloudy
day where
changes
in ambient
ambient
conditions
are
very
frequent
and
severe
as
compared
to
a
normal
hospital
condition.
conditions are very frequent and severe as compared to a normal hospital condition. Secondly,
Secondly,
the homewas
condition
a regular
hospital
environment
during
the the
daytime.
the
home condition
a regularwas
indoor
hospitalindoor
environment
during
the daytime.
Finally,
night
Finally,
the
night
was
a
condition
in
an
indoor
environment
during
night
time,
where
ambient
was a condition in an indoor environment during night time, where ambient and changes in it and
are
changes in itlesser
are significantly
lesser
the other
In these
three
both the
significantly
than the other
twothan
conditions.
In two
theseconditions.
three conditions,
both
theconditions,
LED pairs detected
LED pairs
99%, and 100%, respectively.
drops
97%,detected
99%, anddrops
100%,97%,
respectively.
This
output
was
expected
a cloudy
environment
shows
a higher
variation
in intensity
the intensity
This output was expected asasa cloudy
environment
shows
a higher
variation
in the
and
and
hence
reduce
the
sensitivity
of
the
device
for
actual
drop
in
the
transmitted
IR
intensity.
hence reduce the sensitivity of the device for actual drop in the transmitted IR intensity. Whereas,
Whereas,
the night shows
condition
shows
a lower
amount ofasvariation
astocompared
to home Also,
conditions.
the
night condition
a lower
amount
of variation
compared
home conditions.
these
Also,
these
variations
are
not
as
high
as
variations
for
fluid
change
where
the
chamber
was
variations are not as high as variations for fluid change where the chamber was repositioned for every
repositioned
for every case,
thereby confirming
theFigure
reliability
of the
Figure
shows
case,
thereby confirming
the reliability
of the system.
16 shows
thesystem.
drop count
and16
LED
usedthe
in
drop
count
and
LED
used
in
different
ambient
conditions.
different ambient conditions.
J. Sens. Actuator Netw. 2018, 7, x FOR PEER REVIEW
Figure
Figure 16.
16. Drop
Drop count
count and
and LED
LED used
used in
in different
different ambient
ambient conditions.
conditions.
15 of 19
3.5. End
End Chamber
Chamber Conditions
Conditions
3.5.
During the
the end
end chamber
chamber conditions,
conditions, the
the bottle
bottle completely
completely drains
drains out
out and
and the
the liquid
liquid level
level in
in the
the
During
chamber starts
starts to
to fall.
fall. This
This is
is detected
detected by
by the
the change
change in
in capacitance
capacitance value
value and
and hence
hence is
is not
not affected
affected
chamber
by the
the ambient
ambient lighting.
lighting. According
According to
to the
the theory
theory of
of Equations
Equations (1)
(1) and
and (2),
(2), itit can
can be
be concluded
concluded that
that
by
frequency
is
inversely
proportional
to
the
relative
permittivity,
(higher
frequency
for
empty
frequency is inversely proportional to the relative permittivity, (higher frequency for empty chamber,
chamber,
lower frequency
for full chamber).
The
relativeof
variation
of frequency
is used to determine
lower
frequency
for full chamber).
The relative
variation
frequency
is used to determine
the liquid
the
liquid
level.
As
mentioned
in
section
2.3.7,
the
empty
chamber
frequency
(ECF)
is
65
kHz,
the full
level. As mentioned in Section 2.3.7, the empty chamber frequency (ECF) is 65 kHz, the full chamber
chamber
frequency
(FCF)
is
40
kHz,
for
each
read
out
of
frequency
value
is
stored
in
a
variable
in
frequency (FCF) is 40 kHz, for each read out of frequency value is stored in a variable in Arduino,
Arduino,
named
new frequency
chamber frequency
(NCF),
liquid
(%) remaining
can be determined
named
new
chamber
(NCF), the
liquidthe
level
(%)level
remaining
can be determined
by the
by
the
formulae
shown
in
Equation
(3).
formulae shown in Equation (3).
NCF
ECF
NCF
−−
ECF
Level
× 100
Level
(%(%)
)==
× 100
FCF
− ECF
FCF
− ECF
(3)
(3)
However,as
asdifferent
differentfluids
fluidshave
havedifferent
differentdielectric
dielectricvalues,
values, these
these readouts
readouts were
were performed
performed for
for
However,
different
fluids,
namely
D5,
D25,
and
packaged
drinking
water
and
at
varying
drip
rates.
Figure
17
different fluids, namely D5, D25, and packaged drinking water and at varying drip rates. Figure 17
shows fall
fall in
in observed
observedchamber
chamberpercentage
percentageduring
duringend
endchamber
chamberconditions.
conditions.
shows
Figure
Figure 17.
17. Fall
Fall in
in observed
observed chamber
chamber percentage
percentage during
during end
end chamber
chamberconditions.
conditions.
The slopes in the graph are directly proportional the drip rates. The drips were operated from a
complete fill to a complete empty condition for every readout. The device was calibrated for empty
chamber during calibration loop of each readout and so set a new reference empty for every readout.
It can be observed that the drips didn’t end at a zero. Still, the continuous falling slopes indicate a
drop-in level and can be used as a reliable indicator for chamber end. This can be resolved by
J. Sens. Actuator Netw. 2019, 8, 2
16 of 20
The slopes in the graph are directly proportional the drip rates. The drips were operated from a
complete fill to a complete empty condition for every readout. The device was calibrated for empty
chamber during calibration loop of each readout and so set a new reference empty for every readout.
It can be observed that the drips didn’t end at a zero. Still, the continuous falling slopes indicate
a drop-in level and can be used as a reliable indicator for chamber end. This can be resolved by
improving the algorithm in future work. Analysis of end chamber conditions is essential so that an
alarm can be triggered timely for the hospital staff to take appropriate action, manipulation of these
results is explained further in the Cloud results section.
3.6. LED Malfunction
Another important part of the study was to observe device response if one of the LED pairs fail.
These malfunctions can be of two types, working malfunction or inherent malfunction. A working
malfunction, here, is defined when a pair fails to operate while the device was operating. This kind of
malfunction is more critical as the pair malfunctions during operations and the new readouts should
not detect the false positives. Meanwhile, the other LED pair should keep on detecting the drops
accurately.
Figure
18 shows
LED
pair
used during working malfunction.
J.
Sens. Actuator
Netw. 2018,
7, x FOR
PEER
REVIEW
16 of 19
Figure 18.
18. LED
LED pair
pair used
used during
during working
working malfunction.
malfunction.
Figure
A set of 100 drops was used for this experiment. At drop number 20, the wire from IR emitter
A set of 100 drops was used for this experiment. At drop number 20, the wire from IR emitter
was disconnected to emulate the malfunction of that LED pair. The device was operated at this stage
was disconnected to emulate the malfunction of that LED pair. The device was operated at this stage
for about 40 readings and then the wire was reattached. This test was performed for both LED pairs
for
about 40 readings and then the wire was reattached. This test was performed for both LED pairs
and
the results
results can
can be
beseen
seenabove.
above.The
Thedrawback
drawbackofofoperating
operatingatat
a single
LED
pair
is the
reduction
and the
a single
LED
pair
is the
reduction
in
in the
chamber
area
covered
by the
sensors,
as seen
the graph
above,
the device
will stay
still
the
chamber
area
covered
by the
sensors,
but but
as seen
fromfrom
the graph
above,
the device
will still
stay properly
functional
accurately
detect
each
drop.
order
verifythat
thatthe
thedevice
device is
is counting
counting
properly
functional
andand
accurately
detect
each
drop.
In In
order
totoverify
every falling
every
falling drop,
drop, aa manual
manual count
count was
was also
also performed
performed alongside.
alongside.
An
issue
present,
as
can
be
seen,
was
reduction
sensitivity
of LED
an LED
when
the wire
An issue present, as can be seen, was reduction
in in
sensitivity
of an
pairpair
when
the wire
was
was
attached
again.
This
can
arise
from
lost
calibration
for
LED
pairs
in
the
prototype.
As
the
wires
attached again. This can arise from lost calibration for LED pairs in the prototype. As the wires were
were
manually
handled,
the applied
force applied
can move
the emitters
frominitial
their initial
positions.
an
manually
handled,
the force
can move
the emitters
from their
positions.
For an For
actual
actual
device,
a
working
malfunction
will
happen
when
an
emitter
stops
temporarily,
and
this
will
device, a working malfunction will happen when an emitter stops temporarily, and this will not
not move
it from
its initial
position
hence
no loss
of calibration
willthere
be there
if it works
again.
move
it from
its initial
position
and and
hence
no loss
of calibration
will be
if it works
again.
The
The
second
of malfunction
is an
inherent
malfunction.
Here,the
thedevice
devicewas
wasoperated
operated with
with LED’s
LED’s
second
typetype
of malfunction
is an
inherent
malfunction.
Here,
wire
ofof
100
drops
forfor
malfunction
of
wire removed
removed from
fromthe
thestart.
start.The
Thedevice
devicewas
wasagain
againoperated
operatedwith
withsets
sets
100
drops
malfunction
each
pair.
In an
inherent
malfunction,
the the
device
waswas
ableable
to detect
every
dropdrop
and and
a verification
was
of
each
pair.
In an
inherent
malfunction,
device
to detect
every
a verification
again
performed
with
a
manual
count
for
the
readouts
alongside.
Like
the
previous
case,
the
device
was again performed with a manual count for the readouts alongside. Like the previous case, the
performed
accurately
even after
a reduction
in the effective
chamber chamber
area. Figure
19Figure
shows 19
LED
pair
device performed
accurately
even
after a reduction
in the effective
area.
shows
used pair
during
inherent
LED
used
duringmalfunction.
inherent malfunction.
second type of malfunction is an inherent malfunction. Here, the device was operated with LED’s
wire removed from the start. The device was again operated with sets of 100 drops for malfunction
of each pair. In an inherent malfunction, the device was able to detect every drop and a verification
was again performed with a manual count for the readouts alongside. Like the previous case, the
device
performed
accurately
even after a reduction in the effective chamber area. Figure 19 shows
J. Sens.
Actuator
Netw. 2019,
8, 2
17 of 20
LED pair used during inherent malfunction.
Figure
during inherent
inherentmalfunction.
malfunction.
Figure19.
19.LED
LED pair
pair used
used during
3.7. Cloud Results
3.7. Cloud Results
These tests were performed to provide the device readouts on the cloud dashboard. The first
These tests were performed to provide the device readouts on the cloud dashboard. The first
experiment was conducted in normal hospital operating conditions, a new bottle of D5 was attached
experiment
in normal
hospital
operating
a new
bottle ofand
D5 was
attached
to the IV,was
the conducted
prototype was
calibrated
for empty
andconditions,
full chamber
conditions
the drip
was to
thestarted
IV, theat
prototype
was
calibrated
for
empty
and
full
chamber
conditions
and
the
drip
was
started
a moderate rate. The drip was run for 10 min and output stability was checked for both at
a moderate
rate. and
The drip
was run
for 20a
10 min
andthe
output
stability
was of
checked
both
chamber
level
chamber level
drip rate.
Figure
shows
dashboard
report
volumefor
left
in the
chamber
and
drip
rate.
Figure
20a
shows
the
dashboard
report
of
volume
left
in
the
chamber
and
Figure
20b
and Figure 20b shows a graph of the drip rate on normal operation.
J. Sens. Actuator Netw. 2018, 7, x FOR PEER REVIEW
17 of 19
J.
Sens. Actuator
Netw.
2018,drip
7, x FOR
REVIEWoperation.
17 of 19
shows
a graph
of the
ratePEER
on normal
Figure 20.
20. Dashboard
report of:
of: (a)
(a) volume
volume left
left in
in chamber
chamber and
and (b)
(b) drip
drip rate.
rate.
Figure
Dashboard report
can be
seen,
the
results
obtained
ononthe
cloud
are much
less volatile
and stabilized
from
the
As can
be seen,
seen,the
theresults
resultsobtained
obtainedon
the
cloud
much
volatile
stabilized
from
As
be
the
cloud
areare
much
lessless
volatile
andand
stabilized
from
the
device
end,end,
especially
for volume
left inleft
theinchamber.
As theAs
cloud
resultsresults
are collected
over longer
the
device
especially
for
volume
the
chamber.
the
cloud
are
collected
over
device end, especially for volume left in the chamber. As the cloud results are collected over longer
durations,
hence are averaged
values
rather
than instantaneous
readouts
that
have
lesser
noise
longer
durations,
are averaged
values
rather
instantaneous
readoutsthat
thathave
havelesser
lesser noise
durations,
hence hence
are averaged
values
rather
thanthan
instantaneous
readouts
Another functionality
of
the
dashboard
is
to give out real-time alerts
if any of the rules,
component. Another
functionality of
of the
the dashboard
dashboard is
is to
alerts if
component.
functionality
give out real-time alerts
any of the rules,
violated. To demonstrate this, the device was operated
such
as
volume
left
in
chamber
or
drip
rate,
is
such as volume left in chamber or drip rate, is violated. To demonstrate this, the device was operated
in end
end chamber
chamber conditions.
Figure 21
21 shows
shows instance
instance of
of volume
volume alarm
alarm being
being triggered
triggered as
as soon
soon as
as the
the
in
conditions. Figure
volume left
leftin
inchamber
chamberdropped
droppedbelow
below80%.
80%.
Therefore,
the
graph
changes
the
color
from
green
to
volume
Therefore,
the
graph
changes
the
color
from
green
to
red,
volume left in chamber dropped below 80%. Therefore, the graph changes the color from green to
red,
indicating
a
danger
scenario.
indicating
a danger
scenario.
red,
indicating
a danger
scenario.
Figure
Figure 21.
21. Danger
Danger alarm
alarm for
for end
end chamber
chamber conditions.
conditions.
Figure 21. Danger alarm for end chamber conditions.
4. Discussion
4. Discussion
In the current work, an internet-connected IV drip monitoring platform was prototyped and
In the current work, an internet-connected IV drip monitoring platform was prototyped and
J. Sens. Actuator Netw. 2019, 8, 2
18 of 20
4. Discussion
In the current work, an internet-connected IV drip monitoring platform was prototyped and tested
based on seven points of interests. First, the device was tested for accuracy by matching the number of
drops obtained by the device with a manual count. This comparison was made several times during
the study to ensure proper working when both the pairs were working or one of the malfunctions.
The device had an accuracy of 100%. Second, the device provides a stable output and the results do
not drift with time. The device showed stable outputs for different fluids used and for various drip
rates. Third, the device was able to detect the falling drops even when the administered fluid was
changed four times and at different drip rates. Fourth, the device was tested in different ambient
conditions. Next, the device tested for end chamber conditions, which was done for different fluids.
Here, the chamber was operated from a full condition to a completely empty condition. The level
readouts from the device show a falling slope which indicates the decrease in chamber levels and
hence indicate end chamber conditions.
5. Conclusions
The sixth point of interest was to know if the device will be able to function properly when one
of the LED pairs malfunctions. Two types of malfunction were emulated. The results show that,
during both types of malfunction, the device was able to detect the falling drops accurately. Next,
the implementation of the prototype as an IoT solution was in emphasis. This point was about the
interaction of the device with the user to improve monitoring. It was achieved by data logging over
internet and cloud visualization. In concurrency with experiment and test cases described in previous
points, the results were verified manually, on the device and cloud to check for the consistency of the
system and all three sets of results were coherent. As the device is working efficiently for initial testing,
next step is real-time patient monitoring.
Author Contributions: P.S. was involved in conceptualization, methodology, software, resources, validation,
investigation, writing-original draft preparation, writing-review & editing, visualization, and supervision.
M.K. was involved in methodology, software, resources, formal analysis, writing-original draft preparation,
investigation, and writing-review & editing. A.S. was involved in conceptualization, methodology, software,
resources, and data curation.
Funding: This research received no external funding.
Conflicts of Interest: The authors declare no conflict of interest.
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