Group 27 UR6523002 NMJ30504 Mini Project NTC 3045
Computer engineering (Universiti Malaysia Perlis)
Baraah Ali Omar Balagem
201020037-5
s201020037-5@studentmail.unimap.edu.my
Abdulrahman Fouad Salah Alsuede
201020016-5
s201020016-5@studentmail.unimap.edu.my
Ali Imran bin Saad
201021150
s201021150@studentmail.unimap.edu.my
Smart Thermometer using NTC 100k with the 30‫﮿‬C
to 45‫﮿‬C range (Ni Elves -Lab View)
Group 27-NMJ 30504-Electronic Instrumentation and Measurements
ABSTRACT Temperature sensors are used in many
industrial and scientific applications. The NTC
thermistor is one of the temperature sensors used in
electrical appliances such as MONITORING
PATIENT TEMPERATURE. NTC thermistors are
heat-sensitive resistive elements whose resistance
values decrease rapidly with increasing temperature
[1]. In this article, the applications of NTC thermistors
as temperature controllers in the circuit of a Smart
Thermometer machine are examined. The NTC
thermistors are measured and the properties are
determined as expressions of mathematical functions.
INDEX TERMS Thermistor( NTC 100k), temperature
sensor, nonlinear characteristic, voltage divider,
resistor , Op Amp (Lm741), LED, Smart
Thermometer.
1. INTRODUCTION
Temperature is one of the most important fundamental
physical quantities to be measured, processed, controlled and
transmitted for various health, industrial and domestic
applications. In addition, temperature sensors must be
precise, linear, sensitive, accurate and low powered in the
current technologies to be used in intelligent workplaces,
smart localities, ecological monitoring and warfare
applications. Hence, the sensor’s output readout should truly
represent the measurand of the process.
Human Body is very sensitive to the temperature. If the
temperature is so high it will cause hyperthermia (Medical
News Today,2022). Which is a medical emergency that
occurs when the body is abnormally hot. While if the body
temperature is very low a very dangerous health condition
called Hypothermia occurs to the Human body (Mayo
Clinic,2022). Therefore, we designed Smart Thermometer.
The Smart Thermometer is a system to measure the human’s
body temperature It measures from 30°C to 45°C. This
System divide the range into 5 sections. These sections are
firstly 30-32 which is dangerously cold. Secondly 32-35
which is moderately cold. Thirdly 35-37.5 which is normal.
Fourthly 37.5 – 42 which is moderately hot. Lastly, 42-45
which is dangerously hot. For each of the above sections the
device will light an led depending on the body temperature
and if the situation is very dangerous it will activate a buzzer.
Other than that, the device will give the user a suggestion
based on his Temperature.
The Smart thermometer is using NTC sensor. There are two
types of thermistors: Negative Temperature Coefficient
(NTC) and Positive Temperature Coefficient (PTC). With an
NTC thermistor, when the temperature increases, resistance
decreases, but in this mini project we use NTC 100k.
Thermistors change resistance with temperature changes;
they are temperature-dependent resistors. They're perfectly
suited to scenarios where one specific temperature needs to
be maintained, they're sensitive to small changes in
temperature. They can measure liquid, gas, or solids,
depending on the type of thermistor. The thermistor used in
our project is NTC, that resistance value decreases when
temperature increase.
2. DESIGN OF ELECTRONIC INSTRUMENTATION
The operating range of the system is from 30°C to
45°C.therfore measuring the patients temperature
is the application that we picked for our project
.We have a 5V power supply to the detector circuit
and a 100k Ω NTC thermistor is to be used to
design the detector of the system ,along with other
components to implement our application.
Table of components
NTC Thermistor 100KΩ
Operational amplifier
(LM741)
10KΩ resistor
100KΩ resistor
68KΩ resistor
1kΩ
2.2kΩ
5.1kΩ
100 Ω
LED
NI ELVIS
LAB VIEW
Large breadboard
Small breadboard
Wire Jumpers
Quantity
1
1
3
2
1
2
2
2
3
3
1
1
1
1
In the design for Smart Thermometer, NTC-MF52-B3950
100kΩ Thermistor was used. The Tolerance of the B-value is
±1% in response with a rated resistance for which the
precision is ±1%. The operating temperature range for the
used NTC is between -55℃ and +125℃ which is compatible
with the design. In this type of thermistors the resistance
decreases when the temperature increases .
LM741 is a general-purpose operational amplifier. Firstly, its
null-offset could be adjusted through two pins. Secondly, it is
very stable because its regular input voltage range for is also
very high. Moreover, this device has protection against short
circuits. This operational amplifier can operate between
ranges of 0-70°C. The operational amplifier IC is used as a
comparator which compares two signals, the inverting and
non-inverting signal. In short, this op-amp is the best choice
for analog circuits.
Then NI ELVIS II will Send the information to the
computer. The computer will modify the inputted
signal according to the code in the LabVIEW. In
this project there are 2 outputs firstly the LabView
front panel which Has colored LEDs and A
message that gives and advice based on the body
Temperature. The first output Doesn’t need a
Digital to Analog Convertor Since it is still in the
Computer it Self. However, the Second output
Does. The Digital Signal from the computer will be
converted to analog signal then sent to the NI
ELVIS II. Lastly A specific LED will light up based
on the temperature.
Flow chart
2.1. FLOW CHART AND BLOCK DIAGRAM
Block diagram
The Smart thermometer is A Device that measures
the human body temperature and then Show it to the
user with some suggestions. The Smart
thermometer will begin to measure from 30‫﮿‬C to
45‫﮿‬C. This device contains several components
which are Transducer, Operational Amplifier,
Analog to Digital Convertor, Processor, Digital to
Analog Convertor, and output transducers.
Firstly, the input Transducer which is NTC 100KΩ.
This Sensor Converts the Temperature into
resistance. Then this NTC will be connected with
other Resistance to form a voltage Divider Circuit
that will produce voltage. Since this Smart
Thermometer works in a specific Range another
voltage divider circuit was made. The voltage
divider Circuit will set the lower side of the required
Range (30‫﮿‬C). Since the difference Between the
voltage of the lower side of the range and the
voltage of the maximum required temperature
(45‫﮿‬C) measured by NTC is very small An
Operational Amplifier was used as the signal
conditioning. The OP-Amp Amplifies the
Difference between the 2 sides in order to increase
the sensitivity of the Analog to Digital Convertor
and make the reading more accurate. Then the
output of Op-Amp will be connected to the NI
ELVIS II which has an Analog to Digital
Convertor. The ADC is used to allow the processor
to understand and process the inserted voltage by
converting it from Analog signal to Digital signal.
At the steady state the Smart thermometer is
waiting for the user to Switch it on. when the user
Switch the device on it will begin reading the body
temperature. If the body temperature is between 30
and 32 or between 42 and 45 means the human’s
Life is in Danger. So, Red Led and buzzer will be
activated and a message that notify the user and
suggest calling the emergency number will be
shown then it will measure new temperature. While
if the body temperature is between 32 and 35 or
between 37.5 and 42 means the person is sick but
the situation is not very Dangerous. So, Yellow Led
will be activated and a message that suggests some
home solutions for the situation and suggests
visiting a clinic will be shown then it will measure
new temperature. Next if the body temperature is
between 35 and 37.5 Green light will be activated
and a message that says “the patient's temperature
is normal” will be shown then it will measure new
temperature. Lastly when the user press stop the
device will stop measuring the body temperature.
.
1.1. DESIGN OF TRANSDUCER
minor difference noticeable by the ADC. The ADC voltage
reference is only 5V so the maximum output voltage should
be less than 5V. Therefore, we assume Vout is 5V. Since, this
is differential amplifier the output equation is
𝑅𝑓
𝑉𝑜 = (𝑉𝑚𝑎𝑥 − 𝑉𝑚𝑖𝑛) .
𝑅𝑖
The NTC voltage divider circuit will be connected to the
positive input pin of the amplifier while the 30‫﮿‬C voltage
divider circuit will be connected to the negative input pin of
the amplifier. So, 𝑉𝑚𝑎𝑥 = 0.932V, 𝑉𝑚𝑖𝑛 = 0.551V.
Finding Ri with the Assumption that 𝑅𝑓 = 100𝑘Ω,
100𝑘Ω
5𝑉 = (0.932 − 0.551)
, Ri = 7.6𝑘Ω
𝑅𝑖
Since there is no resistors that is 7.6KΩ in the lab 2 resistors
are connected in series to form 7.3 𝑘Ω.
1.3. Virtual instrument design using LabView
software and Ni Elvis II board.
By referring to the 100kΩ NTC thermistors in the above
table. At the temperature of 30‫﮿‬C the resistance will be
80.65kΩ. While, in the temperature of 45‫﮿‬C the resistance is
43.659kΩ. The NTC will be connected to 10kΩ, 5V supply
and ground too form a voltage divider circuit. So firstly,
calculating the voltage coming from the NTC voltage divider
circuit when temperature is 45‫﮿‬C.
𝑅2
Vout =
x5V
𝑅1+𝑅2
10kΩ
Vout =
x5V, So Vout = 0.932V
43.659kΩ+10kΩ
Secondly, calculating voltage coming from the NTC voltage
divider circuit when temperature is 30‫﮿‬C.
𝑅2
Vout =
x 5V
𝑅1+𝑅2
10kΩ
Vout =
x 5V, So Vout = 0.551V
43.659kΩ+10kΩ
A voltage divider circuit will be designed to form the voltage
of 30‫﮿‬C in order to make it constant. Next calculating the
resistors for the voltage divider.
Assuming R2 = 10kΩ.
10kΩ
0.551 =
x 5V, so R1 ≈ 80 kΩ
R1+10kΩ
So the practical Vout is 0.551 =
10kΩ
R1+10kΩ
x 5V
1.2. DESIGN OF SIGNAL CONDITIONING CIRCUIT
The device will use a deferential op-amp. In order to amplify
the difference between Vmax and Vmin. in order to make any
Figure 6 : The complete lab view block diagram
Now I am going to explain about every main
aspect of this program.
We have an overall while loop function with both
stop control and timing.
Figure 10: calculating the voltage and resistance of the
NTC (transducer circuit) using the Amplified voltage
Using
the
differential
amplifier
equations
then solving it for the V2 which is the
voltage coming from the transducer circuit
Figure 7: the stop control
Create a stop button control in order to stop the
while loop from running and therefor stop the
program.
with
;therefore getting the voltage of the
transducer.
Then using a normal voltage divider equation
and solving for R1 which is the NTC
resistance.
with
,which gives us
,Why do this? The temperature equation
needs it
Transferring the equations into the lab view with
the constant values as shown will give us the results.
Figure 8: the timing function
This block is a function that will control the while
loop in order for it to loop according to a certain time
(milliseconds)
Figure 11: is it in range?
Figure 9: the reading of the amplified voltage
This is how we read the amplified voltage, First we
have the create channel element and make sure it’s
set to AI voltage since we want to read an analog input
voltage then we create a constant at the physical line
port And set it to the analog input that we want to read
from on the ni Elvis board. then add the start element
and connect the task out and the error out of the
channel to the task in and error in of the start element
respectively ,then inside the while loop create and
connect the task out of the start element to the task in
and have the read channel set to analog single
channel.since we are using analog signals and reading
from one input, then create an indicator from the
output data, Named Amplified voltage afterword’s
create a stop element outside the while loop and a
clear element as well and connect the task in/out and
error in/out like the previous parts finally take the error
out from the clear element and input it to a merge error
element.
To check whether the voltage coming out of the
amplifier is in the range to be amplified, using a range
element, comparing between 0 and 5,as 5 is the
maximum voltage that can go into the ADC, and
connecting it to a Boolean indicator for the led to turn
on when the comparison result turn to Truth value.
Figure 12: Temperature Block
In order to find the temperature of that the sensor
measured we take the equation
and do
an inverse calculation to find the temperature T, giving
us
then dividing by 10 to find the
surrounding measured temperature depending on the
NTC resistance and the beta of the 100k NTC ;Then
•
changing everything into lab View block diagram
therefore getting the current temperature value .
•
So that is the temperature is in that range
then that led will light up.
The Led Writing to the physical LED
• In addition to the led lighting on in the
front panel there is another led in the
circuit that will light up according to this
coding
•
Figure 13 : Thermometer Block
This block consist of a thermometer ,which is the
temperature-indicator and a case structure with a color
box inside, connected to the temperature indicator in
order to change the color that fill the thermometer
depending on the temperature .
•
For example when the temperature is between 30
and 32 the color box will be red which will result in a
red colored thermometer and so on depending on the
conditions in the case structure ,and so one with the
other colors of yellow and green.
•
•
Here we have the first and last ranges
connected to a DAQ assistant that is
configured to write digital signals to two
DI/O lines ,with an extended build array
to connect and combine the two ranges
;and the same goes for the rest.
And so the same write function to the
specific DI/O (form the same line we can
connect a buzzer to make a sound when
the temperature is in one of the ranges)
The selection loop for the case structures
• An easy way for loop structures
conditions is implemented here.
Figure 14 : Physical and virtual Led and temperature
conditions.
This block contains four main parts:
•
The compare-in range functions :
• Here we have an element that will
compare a value x with two numbers and
output Truth value is the number x is in
between that range
•
•
•
Here after our x is the measured
temperature (30<x<32)if it’s true then the
it will output a Truth (Boolean) value.
The Led Display on Front Panel
• After comparing in the previous function,
the green wire is connected to a specific
led Boolean indicator
•
•
•
•
The selection is connected in a sequential
manner ;the output of the last element is
connected to the input of the one before it
,and the first element is connected to the
case structure.
Later in the case structure we put the
numbers 0 to 5 and inside is the
statements concerning the case ;
Figure 17 : merge the error out
In this figure there is a merge error element that merge
the error out of the text close file and the clear element into
one error and connect it to the simple error dialog.
Figure 15 : the Message block
This is a string indicator connected to a string constant
inside the case structure that has a message written inside
being displayed according to the temperature using the
previously explained selection loop.
In the figure 15 the case condition is 3 ,which is we look
back it’s when the temperature is between 37.5 and 42
degrees Celsius and therefore the message displayed shows
that the patient is in need of assistance.
Temp. (℃)
30.57
32.5
36.57
38.57
43.36
Measured Vout (V)
0.613
1.155
2.610
3.352
4.317
Figure 18 : merge the error in
In this figure there is also a merge error element that is
placed to merge the error in of the open text file and start
element and connect the merged error into the read channel
error in
3
RESULTS AND DISCUSSION
TABLE III
RESULT OF THE VOLTAGE DROP ACROSS THE THERMISTOR
AND ITS OUTPUT VOLTAGE (VOUT) FOR DIFFERENT
TEMPERATURES
Table III shows the calculated output voltage and the
measured output voltage of each temperature.
Figure 16: writing the data to a text file.
To save our data we need to write the data into a text file
in the way er want it to be displayed
As shown in figure 16 we create an open file element
then create a constant from the operation port and change it
to open or create ,this will allow us to create a new text file
or overwrite an existing file, after words create and connect
a write into file element and a close file element ;to create
the display of our string we use a concreted string that
combine and order our text ;as for numbers we can’t directly
combine then in the string but rater we need to convert them
form a number into a string using decimal to fractional
string element and connect the combined string into the
input of the write into text file element ;when the program
runs it will ask the user to either create or open a text file ,it
will
show
this
way
:
Figure 20: shows the initial state of the program/front panel.
This figure shows the front panel for our program.
When the program runs the thermometer ,the LEDs both
virtual and physical the amplified voltage and the message
box change according to the temperature.
Figure 22: Result When the temperature is between 32℃ and
35℃
when the temperature is between 32 and 35 degrees the
second LED shows the color yellow same goes for the
circuit as the physical yellow Led lights up, and the
message displays that the patient temperature is low and
suggests giving him a hot drink or covering him well.
Figure 21: Result When the temperature is between 30 ℃ and
32℃
After we run the program and when the temperature is
between 30 and 32 degrees the first LED shows the color
red same goes for the circuit as the red physical Led lights
up, and the buzzer output a sound.
As for the message it displays that The Patient temperature
is low and is in need of immediate medical assistance.
This is a figure showing the red physical led on in sequence
with the virtual led.
Figure 23 : Result When the temperature is between 35 ℃ and
37.5℃
This figure shows when the human body temperature is in
the normal state ,as the virtual and physical led light up and
a message saying that the patient’s temperature is normal
,and the thermometer color turns green in sync with the
LEDs.
Figure 25 : Result When the temperature is between 42 ℃ and
45℃
when the temperature is between 42 and 45 degrees the last
LED shows the color red and the physical red led turn on
and the message says that the temperature is very high ,in
the state as well the buzzer is turn on as it’s considered a
critical situation
Figure 24 : Result When the temperature is between 37.5 ℃ and
42℃
when the temperature is between 37.5 and 42 degrees the
fourth LED shows the color yellow same goes for the circuit
as the physical yellow Led lights up, and the message
displays that the patient is having a fever and might be in
danger.
•
For all states the thermometer color
changes according to the temperature in a
similar manner to the LEDs .
4
CONCLUSION
This project was developed using hardware and
software to get the best outcome possible.
Theis project was designed to measure the patient
temperature between 30 and 45 degrees Celsius and
light up an led or a buzzer according to the
temperature and statements, at the same time a user
interface panel displayed a thermometer displaying
the temperature virtually along with 5 LEDs to
indicate the state of the patient with a message that
change according to the temperature.
In conclusion this project applied the concepts of
electronic and virtual instrumentation altogether
with the aid of ni Elvis board and LabView software
and completed the objectives of the project.
REFERENCE
1. “Fever in adults: Symptoms, treatment, and when to seek
help,” Medical News Today. [Online]. Available:
https://www.medicalnewstoday.com/articles/fever-inadults . [Accessed: 28-Jan-2023].
2. “Hypothermia,” Mayo Clinic, 05-Mar-2022.
[Online].
Available:
https://www.mayoclinic.org/diseasesconditions/hypothermia/symptoms-causes/syc20352682 . [Accessed: 28-Jan-2023].
ACKNOWLEDGMENT
We'd like to thank all the lecturers,
- Assoc.Prof.Ts.Dr.Thennarasan Sabapathy
- Ir.Zahari Bin Awang Ahmad
-Ts.Dr.Mohd Ilman Jais
For their lecture, support, guidance also help in troubleshoot
our circuit of mini project during this course NMJ30504
Electronic Instrumentation and Measurement at the Universiti
Malaysia Perlis (UniMAP)
We'd also like to thank everyone who help a lot and contribute
so much to this mini-project.
We'd also like to thank ours family and friends for their
support. Without this support we this mini project would not
be succeedREFERENCES
.