Output from DAC does not match setting

[MrMorden]

I have a 6036E multifunction DAQ card whose DACs do not supply the voltage set on the computer when connected to an instrument.  When set the voltage to 1V and connect a multimeter to the DAC, the reading is 1V.  When I T off the DAC and connect it to both a multimeter and the control input of, for example, a mass spec controller, the voltage goes up to 1.2 V.

In my attempts to diagnose the problem, I have used different cables and swapped the card into a different computer.  After swapping cables, the problem remained, but the voltage that the multimeter read changed.  After swapping the card into a different computer, the card worked normally.

It seems that the problem is somewhere with the computer, but does anyone know what specifically it might be?

Thank you.

[chris_amadasun]

Hello,

Could you elaborate by what you meant by the 6036E does not supply the voltage set in software when connected to an instrument?

Do you mean that if the PC and a standalone instrument are connected on the same power supply?

Or do you mean that when you measure with a DMM you get the right voltage but from a Mass Spec controller the voltage is different?

Thank you

[MrMorden]

I mean that when I measure with a DMM I get the right voltage, but from a mass spec controller the voltage is different.

[Kyle_A.]

Hello,

It seems like the controller is adding an additional load to the line which may or may not be adding extra resistance to the circuit.  Since V=iR, it would only make sense that the voltage increase you are seeing is a result of additional resistance being added but not compensated for, or additional current is flowing when the controller is connected.  The fact that the problem disappeared after using another computer would point to a power supply issue, but I cannot be for sure.  It seems there can only be speculation as to why the card could not hold steady on one PC and not the other.

[MrMorden]

I will try putting a bigger power supply in the computer and see if it helps.