I have a programmable power supply (Sorensen DCR300-16T) that requires a floating programming voltage. From the manual:

(3.9.1) In selecting a signal source, the following should be considered:

  1. The source must be capable of sinking approximately 1 mA (the Programming Current).

  2. A floating (ungrounded) source must be used. All signal programming voltages will, however, have a common return.

I would like to use an analog voltage (ground-referenced) output of a NI PCI DAQ card for this purpose. (e.g. PCI-6713)

In tests, the power supply programming inputs float as much as +/-75 V with respect to the building ground. I suspect that the solution here is to insert something between the DAQ and the power supply input that converts a ground-referenced signal to a floating signal.

What is the conventional advice for how to do this?


1 Answer 1


I doubt you can ground this thing, from a quick glance of the manual, I can't see anything that 'for sure' would lead me to believe that you could connect a DAQ directly to it because it mentions that "a floating source must be used" and the symbol on the schematic is a battery.

It says pin 12 on J2 is a virtual ground, you might be able to build a circuit like this: https://electronics.stackexchange.com/questions/176396/how-can-you-build-a-floating-two-port-vcvs. There are op amps that can be purchased that handle really wide rails +100V, there is could also a be VCC somewhere on J2.

Another solution would be to get a floating isolated power\voltage supply that can be digitally programmed.

It does show that some of the digital inputs can be grounded, but that does not mean the analog inputs can. The analog inputs have capacitors that connect to the analog ground which is floating. There is a reason why the designers didn't ground the control circuitry. The question is, how much current would flow from the analog ground to earth ground, and that's not a question that can be answered without experimentation.

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