Measure Ac Voltage; Induced Interference; Common Mode Rejection; Lead Considerations - Fluke 8588A Operator's Manual

8588A/8558A
Operators Manual
In auto, the gate time is the longest of the cardinal times that will not reduce the
reading rate. If the gate time is set manually, the reading rate is the longest of
RMS filter and gate times.
ACV measurements wait for both the RMS filter settling and the counter gate,
whichever is the longer. If you select long counter gate times, this may slow the
reading rate. The auto times are chosen to not slow the read rate.
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Measure AC Voltage

The sections below explain how to accurately measure ac voltage.

Induced Interference

If interference signals are present or lead interference (noise) takes place during
ac measurements, any induced interfering signals combine with the measured
signal to result in measurement errors. In some circumstances, it may be
possible to filter out the unwanted external signals, but it is generally more
effective to reduce the interference before it is induced. Accomplish this by
operating in a quiet environment, for example, using a screened cage if possible
and using twisted or shielded measurement leads as discussed below.

Common Mode Rejection

The principles of external guarding, outlined in the description of dc voltage
measurement, apply generally to ac voltage measurement. For ac, you gain
further advantage by using the external guard as a shield for the input leads.

Lead Considerations

In all cases, improve ac voltage measurement accuracy by shortening the leads
to the minimum-practical length. Doing this reduces lead capacitance, lead
inductance, and loop area.
Fluke Calibration recommends shielded twisted pair leads for low-frequency
measurements and coaxial leads for low and high frequency measurements.
Take care to avoid measurement errors from the interaction of lead capacitance
and inductance with any source output impedance. For additional information
and guidance, see the Fluke publication
(ISBN 0-9638650-0-5). See the ACV Reading Rate for RMS Filter Settings
Specification in the specifications. See Specifications.
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Peak to peak method: This submenu is active when the Secondary Reading
is set to Pk to Pk. Measured shows the peak to peak as measured in ACV
assuming no particular signal wave form. Sine, Square, Triangle, and
Truncated Sine specify the signal wave form that is measured, and calculates
the peak to peak based on the rms value. For example, if set to Sine, the
peak to peak displayed is 2 x (square root of 2) x rms. Square is 2 x rms,
Triangle is 2 x (square root of 3) x rms, and Truncated Sine is 4.618803 x
rms. Use the Square, Triangle and Truncated Sine selections to measure the
peak-to-peak output of multi-product calibrators like the Fluke 5522A which
have these non-sine wave outputs.
Calibration: Philosophy in Practice