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Users manual
ET3260 and ET3260A
6 1/2 Digit Multimeter
The product adopts true virtual value to send measurement AC signals to measure potential
calorific value in voltage. The average heating power consumed by resistor is in direct
proportion to the square number of the voltage imposed to resistance, which has no relation with
signal waveform. The multimeter can accurately measure true virtual value voltage or current
provided that the energy contained in waveform on instrument's effective bandwidth is
negligible. The effective AC voltage bandwidth of the product is 300 kHz, and effective AC
current bandwidth is 5 kHz.
AC 有效值
AC+DC 有效值
波形
波峰因数（C.F.）
Waveform
Crest factor
AC virtual value
AC +DC virtual value
Multimeter AC voltage and AC current functions measure the true virtual value of AC coupling,
and the product only measures the calorific value of AC parts of input waveform (DC is
controlled). As shown in the above figure, for sine wave, triangle wave and square wave, AC
coupling equates to the value of AC+DC, for these waveforms do not include DC offset.
However, for asymmetric waveforms (such as pulse sequence), Agilent AC coupling true virtual
value measurement will control the existing DC voltage, which benefits a lot. When there is low
AC signal of high DC offset during measurement, AC coupling true virtual value measurement is
quite useful. For example, it is a common situation of measuring AC ripple wave existing in DC
power. However, you might need to understand true virtual value of AC+DC, which you can
confirm by combining DC and AC measurement results, as shown in the following:
For the best AC noise control, you should use integral time of at least 10 power-line periods
(PLC) to conduct DC measurement.
5.2.2 Crest factor error (non-sine wave input)
Generally there exists the following misunderstanding, "Since multimeter can measure signal
true virtual value, its sine wave accuracy indicator is absolutely suitable for input signals in other
waveforms". Actually, the waveform of input signals will influence measurement accuracy.
Generally, signal waveform is described by crest factor which is the ratio between waveform
crest and its virtual value, and the larger the crest factor is, the more energy the high-frequency
harmonic contains. All the multimeters have errors related to crest factor, and crest factor error of
the product is listed in the indicators of AC Characteristic in Chapter 6.
Measurement error caused by signal crest factor can be evaluated as follows:
Error sum=error (sine wave) +error (crest factor) +error (bandwidth)
Error (sine wave): Sine wave error (as indicated in Chapter 6)
Error (crest factor): Crest factor plus error (as indicated in Chapter 6).
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