1 input error detection 24, 2 two-wire measurement 24, 3 connection thermocouple 24 – West Control Solutions TB 45 Temperature Limiter User Manual

Page 24: Input error detection 24, Two-wire measurement 24, Zweileiter - messung 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.

6.3.1

Input error detection

For life zero detection of connected input signals, variable adjustment of the response value for FAIL detection is possi-
ble 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

6.3.2

Two-wire measurement

Normally, resistance and resistance thermometer measurement is in three-wire connection, whereby the resistance of
all leads is equal.
With two-wire measurement, the lead resistance is included directly as a falsification in the measurement result. How-
ever, determination of the lead resistances by means of is possible.

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 a

t 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 mea-
sured value via the scaling.

6.3.3

Connection Thermocouple

If the device is used as a teperature limiter, a double thermocouple must be connected. For measurements in the area
of ambient temperature (0mV) the plausibility is ensured by the control of the 2nd thermocouple. Outside of this range
there is no check of the 2nd thermocouple.

If the device is used as a teperature monitor or limit signaller, no double thermocouple should be connected.
There is no plausibility check. (See connecting diagram Chapter 4.1)

Functions

Input scaling

TB 45

INP2

INP1