5112 input isolation

[jrconsulting]

Does anyone know if there is a coupler that can be used to isolate the input probe from the chasis ground of a pxi-5112 scope? We still want to use the probe for DC measurements as well as ac. Accuracy and calibration is a concern. All of our dif probes have problems in getting consistant measurements.
thanks

[Chris_D]

Message Edited by Chris_D on 12-17-2007 11:06 AM

[Chris_D]

When you say input probe, do you mean your input channel? If so, it is not possible to isolate your PXI-5112 scope from the chassis ground. Please see the link below for more information on isolation techniques and other isolated National Instruments products.

High-Voltage Measurements and Isolation
http://zone.ni.com/devzone/cda/tut/p/id/3410

If you are trying to do AC or DC coupling with your PXI-5112 then this can be selected through the software. You can see how this is implemented in the niScope EX Configured Acquisition.vi example. Please see the NI High-Speed Digitizers help for more information.

NI 5112 AC and DC Coupling
http://zone.ni.com/reference/en-XX/help/370592E-01/digitizers/5112_coupling/

What kind of problems are you having when you say you are not getting consistent measurements? Can you give more details about how exactly you have connected the signal and what exactly you are seeing?

[bosozoku]

I am using 2 5112 scopes in a 1042Q PXI Chassis.  Is there a way to isolate the ground of each one from each other and the chassis ground?  We are trying to take two measurements on two separate circuits simultaneaously.  We do not want to ground the two circuits together because it will affect the measurements on both circuits.  What would that way be?

[Chris_D]

Hey bosozoku,

There is no channel to channel isolation in the 5112. All of the inputs are tied to a common ground and the PXI chassis common ground is connected to earth ground via the power outlet. Are you seeing inaccuracies in your measurements?

[Matt_E.]

This seems to be a duplicate of the question that was asked by the same member in another thread:  http://forums.ni.com/ni/board/message?board.id=150&thread.id=2189