Connecting Temperature Sensors To The Analogue Inputs - Festo CPX-AB Series Electronic Manual

4. Analogue input module CPX−4AE−T

4.3.3 Connecting temperature sensors to the analogue inputs

4−cable design
1
Constant source
of current in the
module
2
Connecting pin of
the CPX module
3
Current supply
for sensor
4
Separate voltage
cable
5
Temperature
sensor
Fig. 4/2: Connection in 4−cable design
Festo P.BE−CPX−AX−EN en 0503b
Each input provides a constant source of current and two
connections for measuring the voltage drop at the sensor. The
voltage drop can be measured at various points, dependng
on the degree of accuracy desired. A distinction is therefore
made between various connecting methods:
The highest degree of accuracy is achieved with the 4−cable
design:
2 cables transmit the current from the constant source of
current (connections lx+, Ix−) through the sensor,
2 cables serve for measuring the voltage drop directly on
the sensor. Connections Ux+ and Ux− are highly−resistive,
so that the cable resistance does not lead to incorrect
measurement.
1 2
Ix+
Ux+
Ux−
Ix−
3
4
5
3
4−11