Scale vertical resolution range

[Bob_Albern]

I am programming a PXI-6733 using LabVEW and would like to scale the 16 bit resolution to the programmed output range. The board currently runs 16 bits over the full +/-10V range resulting in a vertical resolution of about 300uV/step. If I drive a +/-250mV signal, I would like a vertical resolution of, say, 30uV/step. Is it possible to scale the 6733's internal DAC references so the outputs use the full 16 bits of resolution over a smaller output range?

[Norbert_B]

Bob,

the PXI 6733 has only one range for output: +-10 V. the resolution for each bit is always equally distributed over the range, therefore, you cannot create e.g. "logarithmic" distribution of the resolution.
sadly, no dedicated analog output devices from NI have different ranges than +- 10V.
if you want to realize such an issue, you might be interested to take a look on the M-Series MultifuncitonDAQ-devices. PXI 6251/6259/6281 and 6289 have at least two ranges for output (+-10V, +- 5V) and all have 16-bit.

Norbert B.
NI - Germany

[reddog]

While it's true the board only supports a 10 volt internal reference, you can still provide an external reference in order to increase the resolution of your step size.  If you provide a 1 volt external reference, you should get the desired 30 uV/step that you want.

[Bob_Albern]

The help files indicate that a DAQms Channel property "Analog Output:General Properties:DAC:Reference Voltage:Source" should be available. But when I place a DAQmx Channel property node on my block diagram and wire it to my AO Voltage task, Analog Output is not an available property. How do I specify External Source for my reference voltage?

[Bob_Albern]

Turns out my property node wsa set for my other DAQmx device. When I enabled all devices, the Analog output property became available and I was able to control the Output range and resolution.