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Contact body temperature measurement

 
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DoctorLes
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Joined: 30 Aug 2009
Posts: 5

PostPosted: Wed Dec 30, 2009 4:37 pm    Post subject: Contact body temperature measurement Reply with quote

Hello,

I'm interested in making a device to measure body temperature over a specific area, about 3x5 inches square. I would like to graph the average temperature in near real time, in order to reflect very short interval temperature changes. Ideally, the sensor device in contact with the skin would be flexible so it can conform to various body part shapes.

A very accurate reading is essential--such as within 0.25 degrees C, or better.

I envisioned a grid of contact IC-based sensors, such as the Dallas DS 1822, and an Arduino, or similar microprocessor. I've used the Arduino before and would prefer this to learning another system, but I'm open to that.

My question for the group is, what would be a good strategy for getting an average temp from ganged sensors? Or would I need to send each sensor to a separate digital port? I would think I could use op amps to gang them instead; if so, I'm not sure what general configuration strategy would be best.

Any other notions/advice about this project would be greatly appreciated.

Thanks,

Les
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Alan
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Joined: 29 Jan 2006
Posts: 1399
Location: Winnipeg, MB

PostPosted: Tue Jan 05, 2010 11:40 am    Post subject: Reply with quote

I think your strategy is good however I don't think the 1822 sensor has the accuracy you are looking for. I haven't looked it up recently (there may be a precision version that does it though).

I would just read the sensors and send that data back while also adding the values in a counter. Then at the end of the sensor array poll just divide and send back the average also.

For example.
Read sensor 1, it is 25.5 deg. Sent to computer, and add to tempTotal
Read sensor 2, it is 25.2 deg. Sent to computer, and add to tempTotal
Read sensor 3, it is 25.8 deg. Sent to computer, and add to tempTotal
Read sensor 4, it is 25.9 deg. Sent to computer, and add to tempTotal

Divide tempTotal by 4 which would be 102.4 / 4
That would give you an average of 25.6 deg

Those sensors can all be tied to one input pin so with the same number of microcontroller pins you can talk to 1 or 40 of these sensors.
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DoctorLes
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Joined: 30 Aug 2009
Posts: 5

PostPosted: Tue Jan 05, 2010 8:18 pm    Post subject: Reply with quote

Thanks very much for the reply and advice. I shoulda thought of that!
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Alan
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Joined: 29 Jan 2006
Posts: 1399
Location: Winnipeg, MB

PostPosted: Tue Jan 05, 2010 8:29 pm    Post subject: Reply with quote

DoctorLes wrote:
Thanks very much for the reply and advice. I shoulda thought of that!



No problem. Let us know how it works out.
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