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PXIe-4082 (DMM) maximum differential between input and SENSE

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Hi everyone,

 

we're using a PXIe-4082 DMM in combination with a PXI-2527 multiplexer to perform various measurements, which works well. For additional test functionality, we are now adding a programmable PSU PXI-4110, so that power can be supplied to active DUTs. Since some measurements are 4-Wire, we have HI/LO of the DMM connected to COM0 of the multiplexer and SENSE HI/LO to COM1. To increase flexibility, we would like to connect a PSU channel to one of the multiplexer input pairs, e.g. CH31. This would allow us to perform 2-Wire measurements with channels 0..15, while supplying power using any of the channels 16..30. However, this means that the DMM will see the supply voltage on its SENSE lines, since these can not be fully isolated using the multiplexer relays.

 

Now my question: Are there any restrictions on the voltage differential between HI/LO and SENSE HI/LO on a PXIe-4082 when SENSE is not actively used for the measurement (voltage, 2-W resistance, frequency, capacity, inductance, capacitance)?

 

Thank you and best regards,

Philipp

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Accepted by topic author Altatec

Hi Philipp,

 

There are no restrictions on the voltage differential between HI/LO and SENSE HI/LO for this device.
The PXIe-4082 can still be connected in 4-wire mode even when making 2-wire measurements.
There are other DMMs that cannot have the SENSE leads connected when making 2-wire measurements due to an internal switching resistor. However, this is not present on the PXIe-4082, so it should not be an issue. (Can I Use My DMM in 2-Wire Mode When It Is Connected in 4-Wire Mode?)

Furthermore, when making 4-wire measurements, current is forced through the resistor under test (RUT) and a voltage drop across HI/LO is expected.
A different voltage drop will be present on SENSE HI/LO due to their very high impedance. As a result, the voltage drop of HI/LO can be removed from the measurement path when measuring the voltage using the SENSE leads. The section titled "Path Resistance" in the following article gives a more in-depth explanation: Switching Low-Level Signals to a DMM

 

Best regards,
Bendeguz Juhasz
Staff Technical Support Representative | NI

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Hi Bendeguz,

 

thanks for the reply and also for adding the information to the official documentation.

 

Best regards,

Philipp Burch

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