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Biomedical Engineering

Group project

Rodrigo Munguia

on 4 April 2016

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Transcript of Biomedical Engineering

Engineering Practice
Group Project
Biomedical Engineering
Week 6
4/11/13 - 8/11/13
1.LM35 sensor results;
Audio Transducer KPEG163
As the sensor was configured so that 10mV = 1 degree centigrade.
When the temperature increased, the voltage reference of the sensor increased.
When the temperature increased and reached 37℃ the buzzer buzzed (i.e.: 𝑇 > 37℃)
This meant that the output voltage of the sensor was above 370mV.
When the temperature dropped and decreased below 25℃ (𝑇 < 25°) the buzzer also buzzed as the output voltage of the sensor now was under 250mV.
2. Results for the development or the Respiration Sensor System:
The Sensor gave signals which were shown in the oscilloscope.

The change in temperature between the inhaled and exhaled air was monitored through the thermistors, and produced a respiratory signal.
Were the aims met ?

What did we find out?

were they as expected?

What could have been improved?

Overall how we did as a group?
Body Temperature:
What is the body’s way of controlling temperature?
Heatstroke (way above normal body temp)
Hypothermia (way below normal body temp)
What is the importance of measuring body temperature?

Respiration Monitoring:
NTC Thermistors
Resistance measured with small DC current
Voltage drop measured

Operating temperature range is from -55°C to 150°C.

The output voltage varies by 10mV/degree centigrade.

Expected Results
Module: Engineering Practice EE1500

Group Members:
1. Rodrigo Munguia
2. Najma Mohamed
3. Ben Oladokun
4. Mihir Patel
5. Neer Nagda

Personal Tutor: Dr. Reyes-Aldasoro


• Thermistor pushed through plastic tube after being measured for size and holes cut on tube.
• Isolate wires corresponding to each thermistor wire.
• Red shrink wrap placed over the wires and using hot air gun was shrink wrapped.
• Dust mask was fitted over the thermistor.

Breathing Circuit:
Results Analysis
Graphical Interpretation
Graphs showing shallow, deep, rapid and normal breathing rates were all influenced by NTC of thermistors.
Each breathing rate gave expected results when cross-referenced with known wave curves.
Normal measured breathing rate tallied with known eupnea bpm values between 12-20 bpm.

Differential Amplifier Influence
Output of amplifier showed reduced noise when compared to the Wheatstone bridge output.
Amplified output voltage of differential amplifier increased the amplitude of the sinusoidal wave significantly.

Filter Attenuation
A low-pass RC filter aided in reducing noise.
Using the formula: 𝑓_𝑐=1/2𝜋𝑅𝐶 , a degree of remaining noise leftover from the output of the amplifier was removed.
Resistance and Capacitance values were raised for improved cancellation of noise below 10Hz.

Measured Skin Temperature and error
No accurate way to determine the ambient room temperature of the room.
±0.5°C accuracy was lost below 25°C using the LM35 sensor.
Temperature threshold values were not exact.

Error in Measurements (continued)
Sites such as the mouth or ear may have been more ideal for minimising error. (Ambient temperature influence).
Tolerance of resistors used.
Consistency of breathing for wave comparisons.

Graphs: (Results)
In this Graph the Vout of the thermistors is represented by the sinusoidal yellow wave.
This wave was filtered and amplified.
T= 3.2 s
F= 0.3125 Hz
BR= 18.8 Bpm
In this graph patient is producing deep breaths (diaphragmatic breathing).
T= 6.6 s
F= 0.1515 Hz
BR= 9.09 bpm
The patient here is breathing fast (tachypnea).
The Vout here also is amplified and filtered.
T= 0.9s
F=1.11 Hz
BR= 66.7 Bpm
The patient here is showing thoracic breathing which means that the patient is showing shallow breathing.
Voltage is amplified and filtered.
T= 2.0s
F=0.5 Hz
BR= 30 Bpm
Here the patient was breathing normally however this graph is different as the sinusoidal wave is amplified but unfiltered.
BR=14.8 Bpm
Patient is breathing normally but this sinusoidal wave is unamplified and unflitered wave, which is not clear and nor is it smooth,
Patient breathing normally but this time the wave is being produce and recorded only through the Wheatstone bridge.
T= 5.4s
F=0.185 Hz
BR= 11.11 Bpm
Patient breathing normally, however in this graph we can see both signals of the Nasal Airflow sensor using different channels.
Channel 1 (the yellow sinusoidal wave) is unfiltered and as we can see there is some noise and is not as smooth as channel 2 (the blue wave) which is filtered. Both waves are amplified.
The Time period (T) for channel 1 (yellow wave) = 3.4 seconds (avg.) Frequency = 0.294Hz
Breathing Rate for Channel 1 (wave) = 17.65 Breaths per minute.

The Time period (T) for channel 2 (blue wave) = 3.3 seconds (avg.) Frequency = 0.303Hz
Breathing Rate for Channel 2 (wave) = 18.18 Breaths per minute.

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