West Control Solutions KS98-1 - Manual (Page 276)

Input circuit monitor
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Thermocouples
The input circuit monitor monitors the thermocouple for break and polarity error. An error is deter -
mined if the measured thermovoltage signals a value which is by more than 30 K below the span start.
q
Pt100 measurements and transducers are monitored for break and short-circuit.
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Current and voltage signals
With current (0/4...20mA) and voltage signals (0/2...10V), monitoring for out-of-range (I > 21,5 mA or U >
10,75 V) and for short circuit (I < 2 mA or U < 1 V) with “life zero” signals is provided.
Sensor errors are output as digital output ( fail). In case of error, statuses ‘Upscale‘, ‘Downscale‘ or
‘ Subst.val.‘ defined in the configuration can be preset for the input circuit.
Linearization
Thermocouples and Pt100 are always measured over the overall physical measuring range according to data sheet and
linearized according to the allocation table. Linearization is realized with up to 28 segment points by error curve ap -
proximation.
Scaling
mA and V standard signals are always scaled according to the physical measuring range of the transmitter ( x0,
x100).
With transducer measurements, “calibration” is according to the proven method. Bring the transducer to start and then
to end position and “calibrate” it to 0 % or 100 % by key pressure. In principle, calibration corresponds to a scaling,
whereby gradient and zero offset are calculateed automatically by the firmware.
Additional measurements
Dependent of configured sensor type, additional and corrective measurements are required.
The amplifier zero is checked with all measurement types and included into the measurement value. The lead
resistances with Pt100 and transducer, and the cold-junction reference temperature (internal TC) are measured addi -
tionally.
Filter
A 1st order filter is adjustable in addition to the analog part filtering of each input signal.
Sampling intervals
The sampling interval for the INP1 is 200ms.
Linearization error
Thermocouples and Pt100 are linearized over the overall physical measuring range. Linearization is with up to 28 seg -
ments, which are placed optimally on the error curve by a computer program and thus compensate the linearity errors.
As error curve approximation is provided only by segments (polygons) rather than by an nth order polynomial, there are
points on the characteristic in which the residual error is zero. Between these “zero points”, however, the residual er -
ror has very small, but measurable values. For the reproducibility, however, this error is irrelevant, because it would re -
peat itself in exactly the same point and amount, if the measurement would be repeated under identical conditions.
9499-040-82711 Inputs
AINP1 ( analog input 1 (No. 08)) III-276