How to generate Arbitrary waveforms of amplitude greater than 1 V using FGEN PXI-5411 ?

[justsmart]

I am developing a Vc++ application, in which I am using NI-PXI-5411 to generate square waveform of necessary frequency, amplitude, dutycycle & offset.

I use the "nifgen_createArbWaveform" function in my program. This function needs a parameter called "waveformDataArray".

The user manual says, itz range is between -1 & +1. Depending on the gain value, the output will vary.

But I am unable to generate waveform of my required amplitude, say for eg., 4 V (or) 2.8 V

I assumed that, the output voltage = wfmData * gain.
But when I measured the output using Scope, itz coming with different amplitudes.

I need to know, how to map (scale) the wfmDataArray points, according to my
required amplitude.

Can any one help me in this regard ?

Thanx in advance.
--sriram.

[GDEV]

Sriram,

"The user manual says, its range is between -1 & +1. Depending on the gain value, the output will vary."
This implies, that the 12 bit memory resolution corresponds to ±1V if no attenuation is applied (gain=1).

That said, if you downloaded a square waveform that utilizes the full memory resolution you will need to set the gain to 2 to achieve a peak to peak voltage of 4V (±2V) into a 50ohm load (1V peak to peak times gain).

Marian Koop
Software Engineer
National Instruments