SCXI 1322/ 1122 Can't get strain gauge readings

[BBBRG]

Using SCXI 1322 terminal block, 1122 Module in 1000 Chassis. DAQ is ATM 10 16E, windows 2000, LAbview 5.1

Have attached strain gauge to terminal block as shown in manual (Vex- , Vex+ and Ch+) and can get some response in the test panel however there appears to be a quantization error - the voltage readings increase in large incremental steps. Everything is set to default settings and we have tried connecting the Vex/2 to the Ch- but nothing changes.

There are no such problems using a 1121 with 4 channel inputs but as I want to measure 16 channels need to use the SCXI 1322.

CAn anyone help with this problem?!

Thanks

[JustinBritten]

Since you appear to have the strain guage properly connected to the SCXI-1122, and everything works fine in the SCXI-1121, I am thinking that this issue could be related to your scan rate. It is important to remember that the SCXI-1122 needs to be scanned extremely slowly. While the SCXI-1122 and SCXI-1121 may look like similar modules, they are in fact very different due to the relay multiplexer on the SCXI-1122. For more information on this subject, you may find the following Knowledge Base article helpful.

Using the SCXI-1122 Module, a Single Channel Scan Reads Correctly, but Three or More Channels Read Incorrectly
http://digital.ni.com/public.nsf/websearch/AB9DFDC86F04E4D0862564ED00634A7A?OpenDocument

Regards,
Justin Britten

Applications Engineer
ing
National Instruments

[BBBRG]

Having Read this answer I have adjusted the scan rate and still the problem persists. When measuring single channel 0 the voltage measured stepped between two values. Alternatively, after connecting Channel 8 only, without any load on the strain gauge being applied, the voltage reading continually (and slowly) drops from a peak value (2v) to below -4v.
At this point everything has been tried with no success!