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364
Monitoring of DC analog measurements
All processing of the measured signal is performed on the module so that only the min-
imum amount of information is necessary to be transmitted to and from the MPM. The
measuring module receives information from the MPM on setting and the command pa-
rameters; it reports the measured values and additional information—according to
needs and values of different parameters.
Each measuring channel is calibrated very accurately during the production process.
The continuous internal zero offset and full-scale calibration during the normal opera-
tion is performed by the A/D converter. The calibration covers almost all analog parts
of the A/D conversion, but neglects the shunt resistance.
Each measuring channel has built in a zero-value supervision, which greatly rejects the
noise generated by the measuring transducers and other external equipment. The value
of the measured input current is reported equal to zero (0) if the measured primary quan-
tity does not exceed +/-0.5% of the maximum measuring range.
The complete measuring module is equipped with advanced self-supervision. Only the
outermost analog circuits cannot be monitored. The A/D converter, optocouplers, digi-
tal circuitry, and DC/DC converters, are all supervised on the module. Over the CAN
bus, the measuring module sends a message to the MPM for any detected errors on the
supervised circuitry.
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The PST Parameter Setting Tool has to be used in order to set all the parameters that are
related to different DC analog quantities.
Users can set the 13 character name for each measuring channel.
All the monitoring operating values and the hysteresis can be set directly in the mA of
the measured input currents from the measuring transducers.
The measured quantities can be displayed locally and/or remotely according to the cor-
responding modules that are separately set for each measuring channel by the users
(five characters).
The relation between the measured quantity in the power system and the setting range
of the direct current measuring channel corresponds to this equation:
(
Valu e
ValueMin
I IMin
=
+
–
ValueMax ValueMin
–
)
⋅
---------- --------------------------------------------------- -
IMax IMin
–
&KDSWHU
0RQLWRULQJ
(Equation 79)
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