Mydaq AI bad values

[Jimmy770]

Hey everyone,

We are using a MyDaq to read temperature data from a signal conditioner. The signal conditioner outputs a voltage range and then we convert it to a measurement in degrees C. We use to do this with the USB-6009, and this still works if we use the 6009, however with the Mydaq we are periodically getting a negative value. So a graph of the data shows the temperature for a couple samples then a negative value and back to the proper temperature. The frequency of the bad values depend on the sampling rate (ive tried everything from 50-10,000) and the negative values are always just less than zero. You can see the problem in MAX as well.

If I put the 6009 in its place, everything works like it should, why is the MyDaq not working?

Yes, I could use the 6009 but thats not the point :D.

Thanks!

[REDS]

Hi Jimmy,

For the sake of testing, we want to use just MAX's Test Panels. Here are some steps we can try:

1. It would be great if you would have a variable voltage source that you can do a voltage sweep with from -10 to 10V. Check that the values you read are consistent with the values you output from the voltage source.
2. Since you can only choose a Differential measurement from myDAQ, connect your voltage source to AI+ and AI- , while having AI- also connected to AI GND using a bias resistor. 10K is a good value for that.
3. Try this test for both AI0 and AI1.
4. Use "Continuous" Sample mode with 1000 KHz (Rate) and 500 Samples per second. Also try using "On Demand" mode. Both modes should provide the same reading.