analog input problem of 6024E

[northwind]

Hi,

I'm using 6024E MIO card to measure an analog signal and plot the results on a graph. This signal has peak to peak value around 1V(-0.5V to 0.5V). When I run the program, the measured value increases automatically, and when it reaches 10V, the value jumps back to 9.995117V and stuck there. In order to make sure this is a hardware problem, I used Test Panel of Measurement & Automation Explorer to measure the values and I got the same problem. Then I tried different analog input - a sine wave generated by a function generator, which had freq. of 60Hz and peak to peak value of 1V, and the Test Panel show the same problem as before. What causes this problem? Is there any trigger on 6024E card I need to set manually? Thanks in advance!

[RIO-Todd]

It sounds like you're running into a configuration issue or a connection issue.

By default, the configuration of the device will be differential, which means that two input channels are used for every input signal. When configured in differential mode, you need to connect the positive terminal of the signal to channel X and the negative terminal of the signal to channel X+8. For reading a differential signal from channel 0, you will connect the positive terminal of the signal to channel 0 (pin 68) and the negative terminal of the signal to channel 8 (pin 34).

NOTE: If you are working in differential mode with a floating source, make sure to use bias resistors between CH X and and AIGND as well as CH X+8 and AIGND. Bias resistors of 100 kohm will work (the bia
s resistors should be 100 times greater than the impedance of your source). Without these bias resistors, the signal will drift and saturate the amplifier like you are seeing.

You can configure the device for referenced single-ended mode (RSE) a couple of ways. In LabVIEW, you can do this by using the 'coupling & input config' input of the AI Config VI. You will need to change the configuration mode to be referenced single ended within this input cluster. For viewing channels in test panels, you can also change the configuration mode in Measurement and Automation Explorer (MAX) by right-clicking on the device within the devices and interfaces folder and selecting properties. Go to the AI tab and change the configuration mode to RSE. After configuring the device for RSE mode, you will then be able to connect the positive terminal of the signal to channel X and the negative terminal of the signal to AIGND.

I hope this helps.

Regards,

Todd D.
NI Applications Engineer

[northwind]

Thanks Todd! The problem solved! I configured the device for RSE, but used default mode (diff.) in MAX and my program. Thanks again!