Saia-Burgess Controls AG
Manual for PCD2.W745 and PCD3.W745
│
Document 26-796 E
NG06 │ 2018-10-12
2
Configuration
2-3
Operating modes
4 – Wire connection
In this operating mode, the influence of the supply lines is completely eliminated. The
effective voltage on the temperature sensor is measured using two high – impedance
sense lines.
PCD x.W745
R
th
X
+
S
en
sX
+
S
en
sX
-
G
N
D
RTD
Thermocouple measurement
The module PCDx.W745 can be configured to measure temperature using thermo
-
couples.
Physical principle (Seebeck voltage):
The two different metals of the thermocouple generate a small voltage, when the
measurement junction temperature is different from the reference junction tempera
-
ture. This voltage allows to determine the temperature difference between the two
junctions.
To calculate the absolute temperature, the reference junction temperature must be
known.
Internal reference junction (CJC int. – Cold Junction Compensation internal)
In this operating mode, the thermocouples are directly connected to the input clamp
of the PCDx.W745. The module measures the temperature of the clamp terminal and
calculates the temperature of the measurement junction.
The temperature of the input clamp terminal should not be influenced from externally,
for example through forced air ventilation or heat sources close to the clamp terminal.
External reference junction (CJC ext. – Cold Junction Compensation external)
This mode is used when an external isothermal clamp is used. The thermocouples
are connected to the isothermal clamp; the voltage signal from the thermocouples is
transmitted to the module using copper wires.
To calculate the absolute temperature at the measurement junction, the temperature
of the external isothermal clamp terminal must be measured. On the module PCDx.
W745, input 0 is used to acquire this temperature. All selectable temperature sensors
can be used for the measurement of the external reference junction temperature.
