Configuring Auto Range

Configuring Auto Range

Auto Range allows you to measure a signal when you do not know which range to select. The DMM takes a series of measurements and adjusts the range until the measurement falls within the smallest range appropriate for that measurement.

Auto Range uses the same configuration as 5½–digit measurements. Refer to the NI 4065 DMM Measurement Defaults or the NI 4070/4071/4072 DMM Measurement Defaults for more information on the configuration of Auto Range measurements.

Notes   Auto Range does not adjust for the extended 200 MΩ range in 2-wire resistance measurements. You must specify the 200 MΩ range on the NI 4050 and NI 4060. Auto Range is unavailable during diode measurements and waveform acquisitions on NI 407x devices. Auto Range reduces the reading rate of your measurements because the DMM takes an Auto Range reading before each measurement. The NI 4050, NI 4060, and NI 4065 only support Auto Range when the trigger and sample trigger are set to IMMEDIATE. DC current Auto Range on the NI 4071 does not support the 1 µA and 10 µA ranges; for low currents, the NI 4071 only Auto Ranges down to 100 µA. This behavior prevents an electromechanical relay from switching between these ranges (especially when high-compliance voltages could be present) thereby lengthening the life of the relay.

To enable Auto Range, complete the following steps:

• LabVIEW
  1. Insert niDMM Config Measurement into the block diagram.
  2. Set Range to the desired Auto value (refer to the following table).
• CVI/C++/Visual Basic
  1. Use niDMM_ConfigureMeasurementDigits.
  2. Set Range to the desired Auto Range value (refer to the following table).

Values	Description
ON (–1)	An Auto Range measurement is performed prior to each measurement.
OFF (–2)	Use after a measurement that used Auto Range ON to set the DMM to the currently selected range.
ONCE (–3)	NI-DMM picks a range for the first point and uses that range for the remaining measurements.

Tip  Use niDMM Get Auto Range Value or niDMM_GetAutoRangeValue to retrieve the actual range used for a measurement.