DMM Auto Range Time

Updated Jun 27, 2018

Reported In

Hardware

  • PXI-4071
  • PXI-4072

Driver

  • NI-DMM

Issue Details

How long does the auto range on my DMM take to start/stop? When I am using auto range on my DMM, there is a slight delay before the range is applied and my DMM starts providing expected measurements. What is the DMM doing during this time, and how long does it take?

Solution

When using auto range with a DMM, the DMM must acquire some initial samples to determine the appropriate rnage to apply. The duration of this process is provided in the DMM's specification sheet as Auto Range Time. During this time, the DMM takes some initial measurements and uses these values to determine what range it should apply.

For example, the PXI-4071 specifies the following:
  • Auto Range Time, DC V: 5 ms
  • ​Auto Range Time, DC I: 10 ms
  • ​Auto Range Time, resistance: 50 ms
  • ​Auto Range Time, AC V & I: 250 ms
If you are measuring an AC voltage or current, the DMM will acquire samples for 250 ms to determine the appropriate range before it selects this range automatically.

Additional Information

For additional information or specifications for your device, please refer to your DMM's specifications sheet.

For the 408X series of DMMs, we do not have this benchmarked, and so it will not be listed in the specifications sheet. This is because these particular DMMs utilize a software timed process which is less deterministic, and is dependant on the settings, ranges, and other configurations when you're taking measurements.

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