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ManualsBrandsKEITHLEY ManualsTest & MeasurementBench multimeter
51525354555657585960
Front Panel Operation
2001-900-01 Rev. K/ August 2010 3-27
Crest factor: The crest factor of a waveform is the ratio of
its peak value to its RMS value. Thus, the crest factor
specifies the dynamic range of a true RMS instrument. For
sinusoidal waveforms, the crest factor is 1.414. For a
symmetrical square wave, the crest factor is unity. The crest
factor of a rectangular pulse is related to its duty cycle; as the
duty cycle decreases, the crest factor increases.
For the Model 2001, the additional error term for RMS
measurements caused by a high crest factor is specified up to
a value of five. The maximum displayable value is 9.99, or
else it shows “over”.
Note that the crest factor is not calculated if dB or dBm is the
presently selected units.
Low level considerations
For sensitive measurements, external considerations besides
the Model 2001 affect the accuracy. Effects not noticeable
when working with higher voltages are significant in
microvolt signals. The Model 2001 reads only the signal
received at its input; therefore, it is important that this signal
be properly transmitted from the source. The following
paragraphs indicate factors that affect accuracy, including
thermal offsets and stray pick-up.
Shielding: AC voltages that are extremely large compared
with the DC signal to be measured may produce an
erroneous output. Therefore, to minimize AC interference,
the circuit should be shielded with the shield connected to
the Model 2001 INPUT LO (particularly for low-level
sources). Improper shielding can cause the Model 2001 to
behave in one or more of the following ways:
• Unexpected offset voltages.
• Inconsistent readings between ranges.
• Sudden shifts in reading.
To minimize pick-up, keep the voltage source and the Model
2001 away from strong AC magnetic sources. The voltage
induced due to magnetic flux is proportional to the area of
the loop formed by the input leads. Therefore, minimize the