PSM1700 PsimetriQ user manual
10-2
The dc present is given by:
2
dc = 1/2
v() d
0
For a sampled signal, the formula becomes:
i = n-1
dc = 1/n
v[i]
i = 0
where n is the number of samples for an integral number
of complete cycles of the input waveform.
Having computed the true rms and the dc component, the
ac component can be derived from:
rms
2
= ac
2
+ dc
2
=> ac
2
= rms
2
– dc
2
The ac component is also expressed in dB referred to 1mW
into 600 (dBm):
dBm = 20 log (Vac/Vref)
where Vref = (1mW x 600)
or 20 log (Iac/Iref)
where Iref = (1mW / 600)
The peak measurement is simply the value with the largest
magnitude. Positive and negative peaks are independently
filtered then the result with the largest magnitude is taken
as the peak value.
In order to measure surge conditions, the maximum
instantaneous peak value (unfiltered) is also recorded. It is
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