1 input fail detection 24, 2 two-wire measurement 24 – West Control Solutions KS 45 User Manual

Page 24

For using the pre-defined scaling with thermocouples and resistance thermometers (Pt100), the settings
for

InL and OuL as well as for InH and OuH must correspond with each other.

For resetting the input scaling, the settings for

InL and OuL as well as InH and OuH must

correspond.

6.2.1

Input fail detection

For life zero detection of connected input signals, variable adjustment of the response value for FAIL detection is pos -
sible according to formula:

Fail response value

£ In.L - 0,125 * (In.H - In.L)

Example 1:

In.L = 4 mA, In.H = 20 mA

Fail response value

£ 2 mA

Example 2:

In.L = 2 V, In.H = 6 V

Fail response value

£ 1,5 V

6.2.2

Two-wire measurement

Normally, resistance and resistance thermometer measurement is in three-wire connection, whereby the resistance of
all leads is equal.
Measurement in four-wire connection is also possible for input I. With this method, the lead resistance is determined
by means of reference measurement.
With two-wire measurement, the lead resistance is included directly as a falsification in the measurement result.
However, determination of the lead resistances by means of is pos-
sible.

Besides the connection of the both leads of the RTD / R
sensor the 3rd connector has to be short-circuited.

Procedure with Pt100, Pt1000

Connect a Pt100 simulator or a resistance decade instead of the
sensor at the test point so that the lead resistance is included and
calibrate the values by means of 2-point correction.

By means of measurement value correction the resulting
temperature value will be corrected, but not the resistance
input value. In this case the linearization error can increase.

Procedure with resistance measurement

Measure the lead resistance with an ohmmeter and subtract it from
the measured value via the scaling.

- preliminary -

Functions

KS 45

Input scaling

INP2

INP1