offset DMM measurements

[lieven]

I am currently developing an automated measurement system for measuring inductance and resistor values of coils.

As hardware I use a PXI-4072 DMM and PXI-2501 SWITCH.

I am using Labview7.1 and my program is based on the example of niSwitch DMM switch handshaking for what concerns the measurements.

However, the readings I get for measuring 10 coils show a reasonable ofset.

For resistance readings, I notice an ofset of about 3.53kOhm and when I measure an open loop, the DMM returns a value of 8.6kOhm

Also, when I measure an inductance of 280mH, the DMM returns a value of about 400mH.

What can be the reason for this corrupt values? I tried to compensate for it by modifying the configuration values of the DMM, but this did not solve anything.

[J.R.]

Hi Lieven,

Check this link, it can be useful for you.

http://sine.ni.com/manuals/main?searchsubmit=y&q=DMM+measurement

Regards

[lieven]

Thanks for the response Julien.

However, I already found out that the on resistance of the switch causes these offset measurements. In fact, the switch is not very suited for DMM measurements.  I am a bit astonished that the sales representative of NI proposed me this switch, because

it is marked in the DMM manual to use a switch with a very small on-resistance.

Do you know whether it is possible to swap it?

I doubt this is possible, but I would find it the right thing to do for NI.

Regards,

Lieven

[J.R.]

Lieven,

For checking if there is a possibility to swap your board. Please call us at this number 02/757.00.20 (Belgium franch and Dutch).

Regards,

[lieven]

Thanks Julien,

I just called NI and it is possible to replace the switch....

NI has got itself one pleased customer more