206 Keysight B2980B User’s Guide, Edition 1
Function Details
Measurement Time
Measurement Time
Measurement time depends on aperture time, measurement range, and other
measurement conditions and is expressed by the following formula:
Measurement time = Aperture time Overhead time
Aperture time is the time required for measurement, and does not include such
factors as range change or data compensation which would be the overhead time.
Aperture Time
Aperture time is analogous to integration time, which can be described by Number
of Power Line Cycles (NPLC, number of PLC). It is the period of time that the
instrument's analog-to-digital (A/D) converter measures the input signal.
In general, the external noise is superposed to DC measurement signal and it
affects a measurement result.
If the noise is ac noise created from the power line, it can be rejected by setting
the aperture time to 1PLC. Or, if the noise is not created from the power line, the
longer aperture time may be required for noise rejection.
The longer aperture time provides more accurate measurement results but with a
tradeoff of measurement throughput. It is required to set the adequate aperture
time for your measurement application.
If your application simply calls for a true/false or high/low voltage reading, minor
noise will not be a major factor in achieving the desired value, and you can use a
very small aperture time to maximize throughput. The shorter you can set aperture
time the more the instrument acts like a digitizer.
Aperture time has two setting modes:
• Automatic aperture mode
Instrument automatically selects and sets optimum aperture time for
performing accurate and reliable measurements. The instrument provides
three types, Quick, Normal, and Stable, for the automatic setup. See Figure
5-1 for image of the automatic aperture operation. Use Stable if measurement
data is noisy.
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