PXI-4071 hookup - can both HIs and LOs be left connected together for 2 wire impedance, DC/AC voltage, Frequency and Waveform acquisition?

[johngardner58]

Hello,

We are using the DMM and PXIe-6363 card to test a hardware device.  We will also be using a PXI-2530B switch matrix.  We will use the DMM to perform DC and AC voltage measurements,  Impedance measurements (2 wire and 4 wire), frequency and waveform acquisition.  Can the PXI-4071 be left connected in 4 wire mode (black jacks connected and red jacks connected) and still be used to perform all the other measurements (including 2 wire impedance).  This would simplify switch matrix connections.

[Jake_H]

That shouldn't be a problem - the DMM will just ignore the other two wires when doing a 2 wire resistance, voltage, frequency, etc. 

[Jake_H]

If you're looking for more information, see this document. There is an exception for the 4065 when using 2-wire measurement but you should be fine with a 4071.

[Now_With_Underscores]

Thanks Jake for the great info!  I'll note that if we leave the Sense plus lead connected to HI, then we cannot exceed the 500 V maximum voltage to earth ground specifications laid out on page 14 of the 4071 spec sheet.  Also note that if we put the DMM into current mode, we will connect LO to Sense Plus, so make sure your circuit is ok with this (less advisable: don't put the DMM in current mode).

Let us know if you have any topology questions... always curious to see if anything can be optimized.

[johngardner58]

And current measurements?  Just want to be very sure.   One piece I left out: rather than using a terminal block for the multiplexer and Multi-IO we will create a custom board that makes it very easy to plug in the Device Under Test.  This board will have cables that will directly plug into the switch matrix, DMM and Multi-IO and it sounds like we could just have 2 wires to the DMM instead of 4.  So for the board layout we would need to be sure the permanent 4 wire connection would work for all scenarios.   Note  all our stuff is less than +/-15V. 

Given this information  there any reason to configure the 4071 for 2 wire impedance measurements?   I can't think of a reason.

[Now_With_Underscores · Accepted solution]

Current measurements use the S+ and LO leads, but the HI and S- can remain connected.  The problem you run into is if you have an active device on the DMM and you take a 4-wire resistance and voltage measurement with all 4 wires connected, and then switch to take a current measurement... when you do this, you short out the DUT terminals you just took the resistance measurement on.  If the DUT terminal is, say, a 10V power supply, then you've just shorted it out.  Obviously, this isn't an issue if your DUT is a passive device or if you just switch the two unused leads out whenever there's a low impedance active device.

If you want to do voltage, current, and 4-wire resistance, you'll need all 4 leads.  If you want to do voltage and current, you'll need 3 leads, but you could connect the S+ to HI and then just run two wires.  I vote running all 4 wires to your DUT board for maximum flexibility.

2-wire resistance is a must if you're measuring resistance above 10 MOhm.  Otherwise, you can use 4-wire for all measurements.