incoming analog signal with variable mV

[labview1958]

I am trying to measure temperatures between -200c to -100c. I have a circuit that uses a silicon diode to measure the temperature. My circuit measures the voltage across the diode. If it is 1000mV than the temperature is 77K. If it is 998mV than the temperature is 78K. The temperature increaes by -2mV per K. I am using a voltmeter to measure the voltage. Can I just sent the anolog signal into my 6025E DAQ card? Using analog input I can calibrate the signal on my amplitude Vs time chart, is that possible?

[labview1958]

Can I use the analog input for this?

[unclebump]

It depends on how much temperature range you want to read. It looks like the card is +/-10Vdc. You may be able to adjust the scaling on the input to a lower range. What type of resolution do you want in the temperature readings 10 degree, 1 degree, .1 degree?? You may need some signal conditioning/amplification for your signal. The card has 12 bit resolution. If using +/-10 volts input, take 20V/4096. This gives 4.9mv as the smallest readable signal change.

[labview1958]

My temperature accuracy is +-5K. How do you get the figure 4096? Can I just connect an analog voltmeter for calibration? After calibration can I just remove the analog voltmeter and connect the diode terminals to the analog input and analog ground?

[unclebump]

2^12=4096. 12 bit resolution of the A/D.