Omicron CMC 430, Руководство пользователя

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3.10.1 Measurement concept
The following figure shows the signal processing for the analog input mode and the binary input mode:
Input signal
10 kHz/40 kHz
sample stream
Binary changes
ADC
Correction
filter
The input signal is conditioned by an analog front end consisting of programmable gain amplifiers and
an anti-aliasing filter, and then digitized with a sampling frequency of 240 kHz. The further processing
is performed in two independent paths:
• In the analog input path, the gain, offset and delay errors are corrected. The signal is then down-
sampled to 10 kHz or 40 kHz and streamed to the controlling software or device, where the final
measurement results for RMS, powers, harmonics, etc. are computed. The 10 kHz sampling
frequency is used by default. Setting the sampling frequency to 40 kHz provides the advantage of
a higher measurement bandwidth, however at the cost of increased network load and noise
bandwidth.
• In the binary input path, the samples are processed by a binary change detector with hysteresis
and a deglitch logic. Only the binary changes are then streamed to the controlling software or
device.
Since the processing of the ADC data (analog/digital converter) is performed in two independent
paths, the controlling software can use both signals at the same time (for example, in
EnerLyzer Live
and Test Universe ). One possible application for this is checking or setting the deglitch/debounce
parameter configuration.
3.10.2 Analog input mode
In the analog input mode, a variety of measurements are possible, such as RMS, phasor, harmonics
or power measurements. The computation of the measurements is performed in the controlling
software or device on the basis of the pre-conditioned signals delivered by the hardware. Therefore,
the following specifications only apply to the measurement hardware itself and not to the
measurement algorithms. For accuracy specifications of the measurement algorithms, please refer to
the documentation of the concerning software.
Characteristic Specification
Measurement ranges (RMS value of
the sinusoidal shaped input signal) 10 mV, 100 mV, 1 V, 10 V, 100 V, 600 V
Measureable crest factor < 1.75
Sampling frequency (f
s
) 10 kHz, 40 kHz
Measurement bandwidth 4 kHz @ f
s
= 10 kHz with > 80 dB attenuation above 5 kHz
16 kHz @ f
s
= 40 kHz with > 85 dB attenuation above 20 kHz
Typical input impedance 1 MΩ || 170 pF
Technical data
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