PPA5xx/15xx user manual
15-1
15 Phase meter
The phase meter mode is a secondary function which does
not have a separate button. It is selected by stepping
through the operating mode via the MODE menu.
The phase meter uses the terminology of channel 1 for
voltage and channel 2 for current as it is normal to use a
phase meter to compare voltages directly. In this case, the
current input is set to external attenuator in the RANGE
menu, and a voltage probe (oscilloscope probe) can be
used. For optimum phase accuracy, the same type of
voltage probe should be used for the voltage input which
can also be set to external attenuator in the RANGE menu.
Remember to trim the oscilloscope probes if necessary by
connecting them to a 1kHz square wave and adjusting
them for 33.3% 3
rd
harmonic in the harmonic analyser
mode.
The phase meter measures the phase and gain of channel
2 relative to channel 1 using a discrete Fourier transform
(DFT) algorithm at the fundamental frequency. Relative
gain is given as an absolute value and in dB. The ratio can
be inverted to give the gain of channel 1 relative to
channel 2.
To look at differences in gain from a nominal value, an
offset gain can be applied either manually or by pressing
ZERO.
offset gain = measured dB – offset dB