What Is the Input Impedance for the NI Digital Multimeters?

Updated Jun 11, 2018

Reported In

Hardware

  • PCI-4065
  • PXI-407X
  • PXIe-4080
  • PXIe-4082
  • PXIe-4081
  • PXI-4060
  • PXI-4071
  • PXI-4070
  • PXI-4072

Issue Details

I have noticed that on the specifications page for the NI 406x, NI 407x and NI 408x series digital multimeters, input impedance sometimes appears in a table with two different values, as shown below. Which value is correct?

Solution

For the NI 4071/4065, the input impedance specification reads ">10 GΩ, 10 MΩ," and for the NI 4070/4072, the input impedance specification reads ">10 GΩ, 1 MΩ." This means that the impedance is selectable in those ranges and can be either high impedance (greater than 10 GΩ), 10 MΩ impedance, or 1 MΩ impedance, depending on the device.

Note that Auto Range must be disabled to configure the DMM for an input resistance that is not supported on all ranges. This can be done by specifying the desired range manually using the Range input of the niDMM Config Measurement VI.



You can select the input impedance using the NI-DMM property node. After you place the property node on the block diagram, select Configuration » Measurement Options » Input Resistance as shown below.



To get property information, which will indicate what the input impedance is currently set to, right-click the node and select Change All to Read from the shortcut menu. To set property information and control the input impedance, right-click the node and select Change All to Write from the shortcut menu.  Now, you can create a constant or a control that will let you select between 1 MΩ, 10 MΩ, and >10 GΩ as shown below.

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