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3-4
2.
3.
4.
5.
6.
Performance considerations
Warm-up
After the Model 2790 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
Model 2790 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 even-
tually drift resulting in inaccurate readings of the input signal. It is recommended that
autozero only be disabled for short periods of time.
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 measure-
ments, especially if the ambient temperature has changed by several degrees.
klqb
Remote programming can be used to enable or disable autozero
cannot be disabled from the front panel; however, it can be enabled by restoring factory
default conditions.
Attach the test leads to the circuit under test. Use appropriate safety rated test leads
for this application. If over 42V, use double insulated test leads or add an additional
insulation barrier for the operator.
Set the multimeter to the proper function and range.
Energize the circuit using the installed connect-disconnect device and make
measurements without disconnecting the multimeter.
De-energize the circuit using the installed connect-disconnect device.
Disconnect the test leads from the circuit under test.
To force a rapid update of the internal reference points, set the integration rate
to 0.01 PLC and then back to the desired rate (i.e., 1.0 PLC). The NPLC com-
mands to set the integration rate are covered in
Model 2790 SourceMeter
®
Swich System Reference Manual
Section
4.
(Table
3-1). Autozero
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