Configuration
Measured Input
Referenced To:
Va-b
Voltage A
Voltage input B
Vb-c
Voltage B
Voltage input C
Vc-a
Voltage C
Voltage input A
Va-c
Voltage A
Voltage input C
Vc-b
Voltage C
Voltage input B
Vb-a
Voltage B
Voltage input A
Va-n
Voltage A
Voltage input N
Vb-n
Voltage B
Voltage input N
Vc-n
Voltage C
Voltage input N
Va-s
Voltage A
Synthesized neutral
Vb-s
Voltage B
Synthesized neutral
Vc-s
Voltage C
Synthesized neutral
Table 2.2:
DC Measurement Configurations
The Model 931A has two simultaneous measurement modes: wide-band
and narrow-band. Except for harmonics and waveform, all measurements
are made continuously, regardless of the measurement displayed. Changing
the display selection, other than for harmonics or waveform, does not affect
the measurement process. In contrast, the 931A measures harmonics and
waveform on-demand.
The Wide-Band Mode simulates the operation of an extremely accurate
analog rms detector or analog multiplier. Therefore, measurements made
in wide-band include the effect of harmonics within the instrument’s 3.05
kHz bandwidth.
The Narrow-Band Mode is a completely different measurement pro-
cess. Through proprietary DSP state-estimation algorithms, it accurately
estimates the parameters (viz. frequency, magnitude, and phase angle) of
the input waveform. This mode rejects the effects of noise, distortion, and
DC offsets, measuring the fundamental parameters with great precision.
Unlike an FFT, these algorithms are insensitive to the input frequency,
and will make accurate measurements for any frequency within the rated
range of 20-500 Hz.
For measuring a signal with more than 30% THD, or a signal that has
any harmonic with greater amplitude than the fundamental component,
apply the signal to be measured to CH2 and a clean synchronous signal
with the desired fundamental frequency to CH1. The Model 931A will
lock on to the CH1 signal and the CH2 signal can be analyzed.
7
Summary of Contents for 931A
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