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super-d
03-01-2008, 06:17 PM
I'm using the P1117 voltage sensor to read an Analog input from an external temp sensor. From the docs for the voltage sensor Voltage (in volts) = (SensorValue - 500) x 0.06

The external temp sensor (not a Phidget device) gives me 0 to 10 volts and is a linear representation for -30F to 220F. Am I correct with 10 / 250 = 0.04 volts per step?

It must be this head cold because I can't get the calculations to come out right and I know I'm missing something simple.

Actual display on external sensor:67
Phidget reading from voltage sensor=562 (Ratiometric = True) should mean 3.72 volts in
Actual voltage reading 4.11v (my uncalibrated meter)

I would think 3.72 / 0.04 should produce my results but I come up with 93. What am I doing wrong. It has to be something simple.. I hope.

Thanks
David

Alex
03-01-2008, 08:50 PM
If you use any non-Phidget sensor with the 8/8/8, you need to make sure there is only 5V going to/from the board.

super-d
03-01-2008, 08:56 PM
Alex,

The P1117 is the Phidget -30 to +30 voltage sensor. Are you saying it's only good for measuring 5 volts on the input? The external temp sensor is rated at 0 to 10 volts but it's being fed into the voltage sensor.

David

If you use any non-Phidget sensor with the 8/8/8, you need to make sure there is only 5V going to/from the board.

Alex
03-02-2008, 12:56 AM
The sensor board itself cannot be over 5V. The Phidget Voltage Sensor is rated for -30 to +30 V, but the board itself is powered by 5VDC and returns a 0-5V analog signal. Sorry if my explanation isn't too clear. I'm not that well versed in EE stuff. I know concepts, but just not the "lingo";)