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User Manual – Rev J
4.5
Measurements
Standard measurements are always available through the Meas key on the front panel. These
measurements are spread across multiple screens to enhance readability. Switching between
these screens can be done by successively pressing the Meas button on the front panel. This
will cause the screen to cycle through all available measurement screens.
4.5.1
Basic Measurements
The following three measurement screens are available:
Parameter
VOLTAGE
CURRENT
FREQUENCY
POWER
VA POWER
VAR POWER
POWER FACT
CREST FACT
VOLT THD
CURR THD
PEAK CURR
PHASE
Note: The V and I distortion calculations are based on H2 through H50 with the fundamental
component (H1) in the denominator.
Measurements are always running in the background. When the user selects a measurement
screen for display, the AC source first updates all the measurement parameters before
displaying the requested screen. Consequently, pressing the MEAS key may not always bring
up the selected screen immediately. There will be a perceptible delay. This will prevent the
screen from appearing with invalid or blank readouts.
Note that all measurements are AC coupled only so any DC offset will not be reported.
4.5.2
Accuracy Considerations
Any measurement system has a finite accuracy specification. Measurement specifications are
listed in Section 2. When using the AC source for measurement purposes, always consider
these specifications when interpreting results. Measurement inaccuracies become more
pronounced as the signal being measured is at the low end of the measurement range. This is
particularly relevant for low current measurements. The CS Series is a high power AC source
optimized for providing and measuring high load currents. When powering low power loads,
measurement inaccuracies on rms and peak current measurements will greatly affect derived
measurements such as power, power factor and crest factor.
The measurement system on the CS Series uses a digital data acquisition system with a 96
Ks/sec sampling rate and 16 KHz bandwidth. This means that higher frequency components of
the measured signal are filtered out. Any contribution to the rms value of voltage and current
California Instruments
MEASUREMENTS 1
AC rms voltage
AC rms current
Frequency
Real power
MEASUREMENTS 2
Apparent power
Reactive power
Power factor
Crest factor
MEASUREMENTS 3
Voltage distortion
Current distortion
Highest AC current found
Phase angle (relative to phase A (ø1))
CS Series
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