Principle Of Operation - Hitachi HIDIC EH-150 Instruction Manual

1.4 Principle of Operation

The EH-PT4 is able to measure the temperature by supplying constant current to PT100/1000 and by measuring
the voltage drop of it, which is based on the linearity between the resistance of PT100 and the temperature. The
operation of the input part of EH-PT4 is shown below.
PT100 or PT1000
3-wire system
PT100 or PT1000
3-wire system
1. Introduction
2mA
The current is very low.
2mA
Fig. 1.4 Principle of Operation
A0
b0
Voltage
measurement
B0
A3
b3
Voltage
measurement
B3
1-4
Constant
current