Siemens SIMEAS R-PMU, Manual, Page: 43 / 296

6
6.1 Measured Value Acquisition and Processing
43
Digital Fault Recorder, SIMEAS R-PMU, Manual
E50417-H1076-C360-A5, Release 10.2012
Sampling frequencies
The sampling frequencies of the different DAU types are shown in the table below.
Analog-to-digital converter
The analog-to-digital converter operates according to the sigma-delta principle. This method
uses a single-bit converter. A separate analog-to-digital converter is provided for each measur-
ing input to ensure that all measuring signals are processed simultaneously.
In order to avoid aliasing effects during the analog-to-digital conversion, the signal passes an
anti-aliasing filter (low-pass filter) before being digitized. This ensures that frequency compo-
nents in the signal to be sampled that exceed half of the sampling frequency will be suppressed.
Resolution
The analog measured values are sampled and converted into digital values with a resolution of
16 bit (max. 65,536 values). That means that 32,768 values and the “Null value” are possible for
each polarity. The following table contains the resolution of the A/D converter:
Table 6-1 Sampling rates
Nominal frequency
or
binary signals
Sampling
frequency
DAU type
50 Hz 9,600 Hz Analog signals: VCDAU, VDAU, CDAU
Process signals: DDAU
60 Hz 11,520 Hz Analog signals: VCDAU, VDAU, CDAU
Process signals: DDAU
Binary signals 2,000 Hz BDAU
Binary inputs: VCDAU, VDAU, CDAU, DDAU
Table 6-2 A/D converter resolution
Measured value Measuring range A/D converter resolution
Voltage AC 1.5 V
eff
to AC 200 V
eff
13.9 mV
AC 3 V
eff
to AC 400 V
eff
27 mV
Current AC 5 mA
eff
to AC 7 A
eff
0.321 mA
AC 7 A
eff
to AC 400 A
eff
36.9 mA
Process values DC ±10 V 0.34 mV
DC ±1 V 0.033 mV
DC ±20 mA 0.65 µA