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Series 3700

System Switch/Multimeter User's Manual Section 5:

Basic Digital Multimeter (DMM) Operation

Document Number: 3700S

-900-01 Rev. A / August 2007 5

-3

Performance considerations

Warm-up

After the Series 3700 is turned on, it must be allowed to warm up for at least two hours to allow

the internal temperature to stabilize. If the instrument has been exposed to extreme

temperatures, allow extra warm-up time.

Autozero

To help maintain stability and accuracy over time and changes in temperature, the Series 3700

periodically measures internal voltages corresponding to offsets (zero) and amplifier gains.

These measurements are used in the algorithm to calculate the reading of the input signal. This

process is known as autozeroing.

When autozero is disabled, the offset and gain measurements are not performed. This

increases the measurement speed. However, the zero and gain reference points will eventually

drift resulting in inaccurate readings of the input signal. It is recommended that autozero only be

disabled for short periods of time. The internal temperature references used for thermocouple

measurements are performed regardless of the autozero state because they do not have a

significant effect on measurement speed.

When autozero is enabled after being off for a long period of time, the internal reference points

will not be updated immediately. This will initially result in inaccurate measurements, especially if

the ambient temperature has changed by several degrees.

NOTE To force a rapid update of the internal reference points, set the AUTOZERO attribute

for the channel to ONCE. This will update the internal reference points once and stop.

Querying the AUTOZERO setting will show it set to OFF. The Instrument Control

Library (ICL) command to set AUTOZERO is covered in dmm.autozero.

To force a rapid update of the internal reference points for a long period of time and

also to remain on, is to change the dmm.nplc to 0.0005 and then back to the desired

NPLC. Autozero reference will be rapidly updated but continue to be collected.

For example:

dmm.autozero = dmm.ON

dmm.nplc = 0.0005

dmm.nplc = 1.0

Remote programming can be used to enable or disable autozero. Autozero can be configured

from the front panel by pressing the CONFIG key, then the DMM key (configuration includes:

OFF, ON, or ONCE). See dmm.autozero for remote programming information.

Keithley 3730 User Manual

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