Voltage Modulation - Fluke ScopeMeter 190 Series III User Manual

190 Series III
Users Manual

Voltage Modulation

Use voltage modulation to display the modulated output signal.The submenu has selection for
what reference is used for the measurement.
Phase-Phase
Phase-Phase shows the modulated signal between 2 phases. The PWM voltage, voltage peak-
peak, frequency, and volt/frequency ratio show as readings in the top of the display. PWM voltage
shows on the display but not the rms voltage. PWM voltage represents the effective voltage of
the switching output based on the average value of samples over a whole number of periods of
the fundamental frequency.
2 adjusts the zoom level (1, 2, or 3) of the waveform as well as the corresponding
readings.
For Zoom 2, the test tool selects a time base that shows the pulses in more detail and the
readings change to Volt Peak Max, Volt Peak Min, and delta voltage between the upper and
lower levels.
4 BURST (positive or negative) selects either the positive part of the modulated signal or
the negative part of the modulated signal. This selection also applies when you change to
Zoom 3.
For Zoom 3, the test tool selects a time base that shows the edge of pulse of the modulation
signal. A pulse with a high peak is selected automatically to find the highest dV/dt value.
The readings change to Volt Peak Max, dV/dt, risetime, and overshoot percentage when Peak is
selected as Risetime with 4. The risetime measurement is based on the IEC 60034-17
method that uses the 10 % and 90 % values of the peak of pulse. This peak value is used as dt in
the dV/dt reading and the Peak Voltage as dV. Make sure that the slope that is automatically
selected is indeed the pulse of the PWM signal and not of an interference. The start of the slope
must be around the 0-level.
4 LEVEL selects the readings for Delta Voltage, dV/dt, risetime, and overshoot
percentage. The risetime measurement is based on the NEMA MG1 Part 30.1 method that uses
the 10 % and 90 % values of the voltage level. This value is used as dt in the dV/dt reading and
the level voltage as dV.
To change the view of the waveform manually in any of the Zoom modes:
L
1. Push or
2. To change the time base, use the
3. Use the voltage, time, and dV/dt reading to see if the steepness of the switching impulses is
within the motor insulation specification.
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