What type of sensor???

[docJ]

Hello, I am new here and looking to get some help. Thank you in advance.

I have no electrical engineering background. I am a medical doctor doing clinical research, and we are working on a new device similar to a ventilator.

My question is specific to sensors. We need a sensor that can detect movement of chest wall. As the chest expands and contracts, we can sometimes see the movement. However, in an abnormal or pathological condition, this movement can be severely depressed. My question is what type of sensor should be used to 1)detect this movement, and 2)be able to record a count of the number of movements?

Again, thank you in advance.

-Dr. J

 

[keith1200rs]

I seem to remember when I have worked on ECG circuits that you also get a (very) low frequency signal which is actually the breathing. Normally it is filtered out because it is a lot lower than the heart rate frequency. Maybe that would be useful?

Movement can be detected by an accelerometer but the movements you are looking for are very small (in acceleration terms).

Keith.

 

[docJ]

I seem to remember when I have worked on ECG circuits that you also get a (very) low frequency signal which is actually the breathing. Normally it is filtered out because it is a lot lower than the heart rate frequency. Maybe that would be useful?

Movement can be detected by an accelerometer but the movements you are looking for are very small (in acceleration terms).

Keith.

Hi Keith,

Thank you for this info. Can you point me in the right direction as to where to buy this type of "accelerometer". I would greatly appreciate any and all advice regarding the specifics, since I am extremely uneducated this field.

Thank you!

Dr. J

 

[keith1200rs]

Have a look at Analog Devices MEMS sensors: https://www.analog.com/en/mems-sensors/products/index.html

They also do gyroscopes etc. which may be another option.

Freescale may be worth a look as well https://www.freescale.com/webapp/sps/site/overview.jsp?code=DRSNSAXLRTN

There are quite a few manufacturers around although some (such as Murata) are aimed at things like airbags so aren't very sensitive!

I have used the Analog Devices ones for measuring movement for detecting when someone has stopped moving (as part of a system for detecting drowning) so they can be very sensitive.

Keith.

 

[mister_rf]

That’s a project to interface the accelerometer with a microcontroller. The microcontroller will read out the data and process all the necessary calculations. Some examples and tutorials how to implement it here:
http://extremeelectronics.co.in/avr...xis-accelerometer-with-atmega32-avr-tutorial/
http://www.evilmadscientist.com/2007/using-an-adxl330-accelerometer-with-an-avr-microcontroller/
http://www.dimensionengineering.com/info/accelerometers
http://www.pyroelectro.com/tutorials/accel_intro/