Autozero
Autozero is the process of cancelling out the offset voltage from DC voltage
and resistance measurements. When the multimeter is triggered and
autozero is enabled, the signal or induced voltage (resistance measurements)
is measured. The multimeter then internally disconnects the signal or turns
off the current source and measures the offset voltage. The difference
between these readings is the measurement, or the value used to calculate
the resistance.
When using autozero, consider the following:
1. Autozero ensures the most accurate DC voltage measurements;
however, measurement speed is half of that obtained with autozero off.
2. If the temperature of the measurement environment is constant and
the measurements are taken on the same range, autozero can be
turned off with few adverse affects on measurement accuracy.
3. Autozero does not occur following a range change whether it is on or off.
4. When on, an autozero will occur when changing the measurement
function to or from AC voltage.
5. Since autozero shorts the input internally, only the internal DC offset
to the A/D is measured.
Enabling Autozero
The
MEASure
and
CONFigure
commands turn the autozero function on.
The command used to turn autozero on and off is:
CALibration:ZERO:AUTO
mode
| ONCE
where:
mode
= ON
(an offset voltage measurement is made after every
measurement of the input signal) or
OFF
(turns the autozero function off).
ONCE -
performs an offset voltage measurement after one measurement
of the input signal. The offset is then subtracted from all subsequent
measurements.
Querying the Autozero
Mode
The autozero mode is queried with the
CALibration:ZERO:AUTO?
command. See Chapter 5 for additional information.
Chapter 4
Understanding the HP E1326B/E1411B Multimeter 99
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