Cant read some analogue inputs on usb 6008

[Windy Miller]

I'm using a USB 6008 to read 3 differential analogue inputs, one digital input, and the counter input.

When looking at the analogue inputs in MAX, the first analogue input functions correctly, but the second two are just floating around the 0v mark.

A variable voltage signal is present on the 6008's pins so its not a connection problem.

I've played around with the settings in MAX and just can't get the 6008 to pick up the signal.

I'm using LV7.0 and MAX 3.1.1 as I think this is the latest version compatible with LV7.0.

Any pointers would be greatly appreciated.

[GrahamG]

Hi Windy

Can I ask a couple of questions about your setup? First are you trying to do these all simultaneously or at separate times. Second when you say that you are playing around with the settings in max what have you been trying.

Will you post some screen shots of the test pannel in max on each channel. You should be feeding your signals into pins 2, 5 and 8 and I cannot see why is shouldnt pick up a reading there. Does thye 6008 pass a self test?

I look forward to hearing from you

best regards

[Windy Miller]

Hi Graham

The unit in question is 20 miles away, but I'll get some screenshots tomorrow.

In the meantime, in answer to your questions, yes, these are all happenning simultaneously. I have 3 while loops running concurrently, one for the digital input, one for the counter input, and one for the analogue inputs.

Regarding playing with the MAX settings, what I mean is that I've been changing between the differential and RSE settings, and no permutation seems to work.

The 3 analogue signals are differential ones, and are wired correctly (I've triple checked this!).

The strange thing is is that the first analogue channel, the digial input and the counter all work correctly.

Also, when I swap the 6008 with another one (I have 4 of these test configurations built) the same problem exisits, so I know its not a hardware problem, or is extremely unlikely to be.

Chris

[GrahamG]

Hi Chris

This does indeed sound like a strange problem. If you were receiving a floating voltage from you card then I would expect this not to stay at a steady 0V. It is more likely that you somehow are not reading from these channels. I have an Idea that in you code you have started reading from the first channel but it has not exited the loop from reading this channel so has not started to acquire on the others.

Your counter and digital will be running on separate threads and so will not be effected.

Will you please post the code containing the analogue input loop and I will take a look and do my best to advise.

Thanks and best regards