Hioki 3290-10, Instruction Manual

Page: 83 / 152

4.5 Current Integration
77
1
2
3
4
5
6
7
8
9
10
M
easurement
P
ro
cedure
About the Measurement Process
The DC measurement method of this meter separates the input
signal into positive and negative polarity components.
A typical current integrator passes the signal through a low-pass fil-
ter (LPF), then converts the waveform (e.g., square wave) into DC
for measurement. These current measurements are then summed
to produce the integral. However, because of the inherent
response time of the low-pass filter, brief negative pulses cannot
be detected, as illustrated below. As a result, the negative integral
is zero or too small, and the positive integral may be too small
(although there is no net error in the total integral).
On the other hand, this meter splits the waveform into positive and
negative components before processing. Each polarity is then pro-
cessed independently so there is no loss of either, and therefore
more accurate detection. As a result, it is possible to measure very
slight control errors by positive and negative integration. The total
integral value is obtained by summing positive and negative inte-
grals. Sampling is 10 time/s (alternating polarities 5 times/s).
In AC and AC+DC modes, all waveforms are made positive by
RMS-DC conversion, so there is no meter-inherent difference as
described above.
0 A
0 A
After LPF
Negative pulses not detected
Short negative pulses
0 A
0 A
0 A
After LPF
Short negative pulses
After separating polarities