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Setting the gain on a SCXI-1102 Channel via MAX has no effect.

I am using a PCI-6034E board with an SCXI-1102 signal conditioning unit and an SCXI-1303 32 channel terminal block.

To measure 0...100mV signals the gain on a channel has to be set to 100, which I "can" set with MAX, however setting the gain to 100 via MAX has no effect i.e. a 10mV signal monitored on the test pannel after setting the gain to 100 remains a 10mV signal (no amplification, poor signal resolution).

The same occurs when using the "Obtaining Gain Applied by the Entire System, DAQ, SCXI for a Channel in an SCXI System" to read and "Setting a SCXI Module Gain" available in the NI Developer Zone. The Get Gain Levels vi always indicates a gain of 1, no matter what is set in MAX or set via the Se
tGain vi.

Am I missing something trivial or is it likely that there is an error with my SCXI-1102?
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CP,

The gain for your SCXI-1102 module can be set in MAX via the Properties page for your module. This will be the default gain for the SCXI module and used only when you do not define input limits in software or when you define input limits as 0 max and 0 min. If you wish to change the gain, then you will define input limits and the appropriate gain will be configured by the driver. This best gain will first be applied at the SCXI module and then at the DAQ card if more gain is needed.

Additionally, when you configure a Virtual Channel in MAX's Data Neighborhood, you define an input range and this is used to determine gain much like the software input limits terminal in LabVIEW. Therefore, if you use a Virtual Channel the gain will be set by the range and not by what is configured in MAX for the SCXI module. If you choose to use an SCXI channel string, instead of a Virtual Channel, in LabVIEW, then input limits will define the gain or, if none are selected, the default gain will be used.

The gain will also be transparent to the user. Meaning that if you apply a gain of 100 to a 1mV signal you will not read 100mV. You will still read 1mV; however, the original 1mV signal was amplified by the SCXI module and/or DAQ card and the full resolution of your DAQ card was applied over this smaller range.

So, taking a look at the example you pointed me to, "Obtaining Gain Applied by the Entire System, DAQ, SCXI for a Channel in an SCXI System," this will return the gain configured in MAX only if you use an SCXI chanel string, and only if you do not specify input limits. Otherwise the gain will be configured per your input range.

How Do I Set the Gain for My Analog Input Channels in LabVIEW?
http://digital.ni.com/public.nsf/websearch/cba83550ab782d1c862566210061beb9

Why Is My DAQ Gain Affected When I Remove "ob0" from My SCXI Channel String?
http://digital.ni.com/public.nsf/websearch/E2822BF07C458189862569D20073FF6D?OpenDocument

Regards,
Justin Britten

Applications Engineer
National Instruments
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OK I've now set the input range in the Virtual Channel to Min 0 Max 0.0999 and am now able to resolve 0.1mV and less, so it works.

Thank you Justin!

Best Regards,
Patrick Coray
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