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VA Check Screen
33
VA Check Screen
Press at any time to access the VA Check screen, which displays volts
graphed against amps. Press
a second time to exit the VA Check screen
and return to your starting point.
With the VA Check screen, the Tester displays one cycle of the fundamental
frequency (current on the vertical scale, voltage on the horizontal scale). The
resulting graph can appear as a straight line, a stepped line, an ellipsoid, or as
some other pattern that you would normally expect to see on an oscilloscope
with two input channels.
Use the VA Check screen to show the phase shift of the fundamental
frequency and detect the existence and severity of nonlinearity caused by
harmonics. It could be that the VA Check screen may simply show that you
have clamped the Current Probe in the wrong direction. Figure 15 shows
some typical VA Check signatures.
When the Tester is set for autoranging (
AUTO), ranges for the vertical and
horizontal scales on the VA Check screen are adjusted automatically to
provide a meaningful display. If the Tester is set for manual ranging (
MAN),
both scales (ranges) are fixed; you may have to choose
AUTO (press for
1 second) or select an appropriate manual range in either V or A, or both
functions (i.e., press
briefly for each range change).
Note
V or A ranges cannot be changed while in the VA Check screen.