Dynalyzer – High Voltage Unit
OPERATION MANUAL
25
Figure 15:
Current vs. Conduction Angle
Rms (root means squared) current measurement is essential. Rms current is the heating value of
that current. In the relationship l
2
R=power, the current is assumed to be the DC or rms value. Most
DVMs or VOMs have their ac average value of a rectified sine wave. Measurement of other
waveforms results in an erroneous, and often misleading answer. Other DVMs and VTVMs are
calibrated on the basis of peak voltage of a rectified sine wave. The use of these meters with
phase-controlled waveforms, often found in SCR circuitry will be totally misleading, as no change
in voltage will be measured until the SCR is phased back to 90° or less.
If desired, a graphical integration technique, similar to that described for mA measurement may be
used. In the case of rms measurement, divide one complete cycle (1/60 sec.) into 20 parts.
Measure the amplitude at each point and square it. Take the sum of the squares and divide it by
the number of points being counted (20 for example). Take the square root of this number. This is
the rms current. The procedure is outlined in Figure 16.
INPUT
WAVEFORM
Iav
Ip
Ip
Irms
CONDUCTION ANGLE (%)
