Sensor interface with a Non-Phidget ADC converter

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Taka

Sensor interface with a Non-Phidget ADC converter

Postby Taka » Fri Oct 10, 2008 2:55 pm

Greetings,

I've searched through the forum and wasn't able to find how to map the values of a sensor being interfaced with a non-phidget ADC converter.

The device that I'm using is a Bluesentry node, that allows up to 8 channels, i.e. sensors, to be connected and for their respective values to be transmitted over a bluetooth connection. Bluesentry provides, for each channel, a 16-bit precison in the 0-5 Volt range. Just for those of you who are curious, you can check Bluesentry at http://www.rovingnetworks.com/bluesentry.htm.

I was able to solder a Precision Temperature Sensor (Product ID = 1124) to the Bluesentry unit, and I'm also able to obtain readings from the sensor. The problem is that I cannot map the 16-bit value that I'm able to read into a meaningful temperature value.

I've gone through the Precision Temperature Sensor 1124 product manual, available here http://www.phidgets.com/documentation/Phidgets/1124.pdf, which mentions the following formula:

Temperature (Cº) = ((Vin * 200) * 0.2222) - 61.111

Yet, when I employ the above formula, with Vin as the sensor reading obtained, I obtain values in the 35-40ºC range. Yet the room temperature where I tested the temperature sensor was set by the Air Conditioner to 24ºC.

I've also noticed that the initialization code provided for the temperature sensor in the source code for Phidget 21 MSI is quite complex and seems to configure the temperature reading whilst contemplating the sensor model and also with data provided by some lookup tables.

Shouldn't the formula provided in the product manual be enough?

I would appreciate, a lot =), any suggestion, specially if someone has any idea regarding some possible factor that I'm not contemplating, or if any of you has had hand-on experience with this kind of problems.

Thanks in advance.

Cheers

fitchett
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Postby fitchett » Fri Oct 10, 2008 5:12 pm

The PhidgetTemperatureSensor in the library is for the 1051, not the 1124.

The formula should be enough - you might want to verify the 1124 is receiving 4.75-5.25VDC, and the Bluesentry is measuring the returned signal with respect to the 5V supply for the 1124.

Chester

uopes

Postby uopes » Mon Nov 10, 2008 10:27 am

hi Taka!

Can you help me with Bluesentry?
I'm using it in a project that i have to acquire data from a circuit but i'm not recoignizing the data i'm receiving over HyperTerminal..
How did you get thru with it!?
Did you have any problems with Bluesentry?

Data i'm receiving is like this:
"-009A A5DE
-009B B07B
-009C 80A4
-009D 938B
-009E 9CC0 "

either i'm sending signal or not..

thanks,
Rui Lopes :)


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