I've a PXI 1044 chasis fitted with function generator card (PXI 5402). Noticed a problem when using DC offset. When I set the DC offset to 1V, the GUI displays it properly but when measured using a oscilloscope, it shifts up by 2V. Has anoyone seen this problem? Is it a s/w or a h/w issue? Please help!!!
Most likely you have set the load gain as "same as source" which is
50 ohms by default. The driver will automatically generate twice the voltage so
that you get the requested voltage at the load. This is because you have a load
and source impedance of the same value which will act as a voltage divider.
In NI-FGEN driver, there is a property node "Load Impedance". You
can set the value for this property node as "1M" and it will also
solve the problem. Look at the picture.
Hope this helps,
Message Edited by Yardov on 02-27-200704:09 PM
Gerardo O. RF SW Engineering R&D National Instruments