I am using the type K thermocouple with the AD595. I can get the expected output on the oscilloscope. But when I connected the AD595 with the USB-6001 , in differential mode, the output drops to -2V after regular interval. Even in RSE connection, I am getting the same response. See the attached images
I am not sure why my circuit output is OK on the scope but not with the USB-6001?
Any suggestion how should I connect as I have run out of the ideas.
I also noticed that USB-6001 body gets very warm just after few minutes of powering up, though I am only using my laptop USB port to power it up!
Could it be the internal hardware issue?
Given that you have verified the output of the AD595 to see that this unexpected signal isn't coming from the chip I recommend checking the input of the USB-6001. There are a few possible ways of doing this:
-Connect an AO to an AI and then use test panels to generate a signal on the AO and monitor this on the AI
-Use a known voltage source, for example a battery, and connect this to AI
Depending on the frequency of those drops it could be that the source of them is coming from some interferance from the mains supply. Make sure that the device and any of the wires connecting to it aren't running near mains cables or anything that might generate a lot of electrical noise such as motors.
Sorry for late reply.
It turns out to be hardware fault with my new USB-6001. It has been replaced and now my circuit perfectly works fine!