12-14-2012 09:15 AM
Hi! I have a NI USB-6211 that I want to use for measuring a signal in differential mode. However there is problems acheiving the correct results. In the figure below I measure over a single 1,5 V AAA battery, with the device set for differential measurement (and terminated AI0 & AI8). As you can see the signal is quite noisy, and also for each 20 ms the signal drops to 0 V for some milliseconds. The same behaviour occurs for all channels!
If using RSE (connected AI0 & AI GND or AI8 & AI GND), the DAQ shows the expected measurement without any noise as shown below.
What do I do wrong, or have the DAQ failed?
Solved! Go to Solution.
12-16-2012 01:29 AM
Hello Andres,
If you check out Pseudodifferential versus Differential Input Configurations, you can see that for floating signal sources, we actually recommend you to use pseudodifferential connections when you have a floating signal source, like a battery. This means that you need to connect a small resistor between AI(-) (AI8, in your case) and AI GND. Try that and see if it works.
12-16-2012 03:44 AM
Thank you, that solved my problem!