NI 6221 37 PIN Analog Input problem

[Mechatro_Nika]

Hello,

I have a NI 6221 37 PIN card and would like to read analog voltages. I am contacting my signal cables via a D-SUB connector, like one you can see on the pic. It has 37 PIN, mother D-SUB connection on the front and a solderable backside.

http://hu.farnell.com/fci/dc37s064tlf/connector-d-sub-receptacleacle/dp/2293762

My problem is, that I always measure + or - 10,6 V, when the range is set to +/-10 V and I measure +/-5,3 V at the range of +/- 5V. I tried almost all types of connections from page 58 of this manual (ground referred NRSE would be my preferred):

http://www.ni.com/pdf/manuals/371022k.pdf

I ran the NI DAQ Diagnostic Tool 2.1, the self-test of the MAX and none of them reported any failure. What can be the problem?

Thanks!

[Henrik_Volkers]

Sound like open analog inputs that a saturated by bias currents.

If you shortcut the AI0 to AGND, what do you measure?

[Mechatro_Nika]

I tried it and had the same reading. I also shorted it with the digital GND and got the same...

[Henrik_Volkers]

shure you made the correct connections?

I still vote for open inputs

[Mechatro_Nika]

I tried it again, and still got the same results. I also got a NI 6008, and with the same connections that one works. But I still want to use this 6221. I do share your opinion about open circuits, it's just that I cannot imagine what I forgot. Is there a PIN maybe that I always have to connect to a supply or something? So far I only connected the signal and the ground wires.

[Henrik_Volkers]

Both cards have different connectors 😉

I have seen (not only once, not only fabricated by me 😉 ) false counted pins on multi pin connectors, broken wires, cold solder connections, ...

[Zody]

I agree with Henrik at this moment, check out if you have the proper soldering, it seems more of a connection issue than device problem.

Best regards,

I.R.

[Mechatro_Nika]

You were right, it was really the connections. Now it is workig. As a side note: the pinout drawing on the datasheetconfused me a little, as it numbers the pins as you  can see them on the mother connector and not as on the card-connector. But anyway it is OK now. Thanks.

[Henrik_Volkers]

Thanks for comming back 🙂