Measuring low voltage with 6115, C++ application

[Broccoli]

I want to measure a signal +-0.5V. I am using the SCAN_Op function to take 1000 readings, and 6115 mulitfunction card, which has a 12 bit analogue input.

The problem is, the 6115 is measuring between +-10V, so my +-0.5V signal is only using a few of the bits.

How do I scale down the voltage range in C++?

[Tiptop]

Hello,

All that you should have to do to take advantage of the different gain settings on the board is utilize the SCAN_Setup Function. The last argument is an array that contains the values of the gains for each channel in the scan. For more help, please refer to the Function Reference Help, which can usually be found by going Start->Programs->National Instruments->NI-DAQ->Traditional NI-DAQ Function Reference Help.

Also, for valid gain settings, please refer to the PCI-6115 Users Manual
http://digital.ni.com/manuals.nsf/webAdvsearch/350F82C34DFF8BE586256D2C004E2759?OpenDocument&vid=niwc&node=132100_US

Also, note that the manual refers to ranges. The default range is +-10V, so all gains settings are in reference to this range, and .5, .2 are -1, and -2
in integer format.

Thanks,

Justin Tipton
National Instruments