Multidisciplinary Senior Design I
P10054 – Monitoring Device for Human Smoking Behavior
Deep Inhalation Puff
Feasibility Test Plan
Introduction
Experiments are performed in order to evaluate the range and accuracy of several types of respiration
sensors, in preparation for integration with the designed product. Analysis is conducted using bench
power supply, signal generator, and oscilloscope. Data is captured via PC for further analysis.
Equipment
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Bench DC Power Supply
Signal Generator
Multimeter
Oscilloscope
Computer DAQ
Microsoft Excel
Linear Strain Sensor
Inductive Band
Piezoresistive Sensor
Modified: 11/17/2009
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Multidisciplinary Senior Design I
P10054 – Monitoring Device for Human Smoking Behavior
Procedure
Linear Strain Sensor
1. Supply sensor with +5 V and -5V from power
supply
2. Connect Vin+ and Vin- wires to Oscilloscope
and Computer DAQ
3. Strap sensor around chest of test subject,
outside of clothes. Location for males is
approximately one inch below nipple line.
Location for females is comfortably below
breasts.
4. Instruct subject to sit comfortably straight in
chair, and relax.
5. Monitor oscilloscope to verify that sensor is
Figure 1
performing.
6. Begin recording 60 seconds of data on the PC.
7. Allow patient to breathe normally for 30 seconds.
8. Instruct subject to inhale as deeply as possible, then exhale as fully as possible.
9. Repeat step 8 two more times.
Figure 2
Using the female-female gender changer, the proper pins to hook up the BIOPAC belt are:
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GND (2)
Signal (3)
+5V (4)
GND (6)
-5V (9)
Modified: 11/17/2009
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Multidisciplinary Senior Design I
P10054 – Monitoring Device for Human Smoking Behavior
Results
Figure 3
Modified: 11/17/2009
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Multidisciplinary Senior Design I
P10054 – Monitoring Device for Human Smoking Behavior
Figure 4
Modified: 11/17/2009
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Multidisciplinary Senior Design I
P10054 – Monitoring Device for Human Smoking Behavior
Discussion
As shown in the figures above, it is necessary to amplify the response of these circuits in order to obtain
meaningful results. Quantization is shown as an artifact of the analog to digital conversion in the DAQ
hardware. This is because the input signal is only varying in the 20 mV range, which is far below the
designed range of the DAQ.
There are two solutions presented:
Amplifier Circuit with Bandpass Filter
Recommendations from BIOPAC for their sensor are a gain of 10, with a bandpass filter between 0.05 Hz
and 1 Hz (Source: http://www.biopac.com/FAQPage.ASP?id=278). According to our calculations, this
puts the voltage response in the range of ~.5 VDC . Experimentation will have to be conducted using
gain between 20 and 40 in order to find an ideal range in 0-5 V. The amplifier/filter circuit will need to
be analyzed for current draw.
The SleepSense inductive band has an even lower voltage range, according to our test. Gains of 100 and
1000 did not raise the response to a level where visible quantization was not observed on the DAQ. The
base voltage response on the inductive sensor also varied by as much as 5V, which would need to be
compensated before amplification in order to obtain a final signal between 0 and 5 Volts. Initial
indications are that design of the signal conditioning circuits is not a trivial task.
Next Steps
Derek
 Design signal conditioning circuitry to bring sensor signals to 0-5 Volt range
Frank
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Support Derek based on reference circuit design
Rich
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Investigate voltage response from inductive band for frequency response
Generate follow-on testing plan for signals and conditioning
Modified: 11/17/2009
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