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What is a PT100 sensor ?
The PT100 is a sensor Based on resistance measurement principle.
Material is platinum and resistance value is 100 ohm at temperature 0 °C
Platinum has a positive resistance temperature factor; resistance increases with rising temperature
Resistance variation is a function of temperature; 0.39 ohm per 1 °C.
Long term stability is the main difference compared to other temperature measuring methods.
Pt100 sensor structures
One sensor structure can include also several Pt100 resistances: 1, 2 or 3 Pt-100.
Most common is 1 Pt-100.
For different measuring circuits the resistance element can be produced in different versions: 2, 3 or 4-wire connection.
Most accurate is 4-wire.
Even as a standard version the industrial Pt100 sensor is vibration proof and additionally it can be produced as an extra vibration proof version for extreme circumstances.
What does 2, 3 and 4 wire connection mean?
A resistance temperature detector (RTD) can be connected with 2, 3 or 4 wires.
The 2-wire connection needs only 2 wires, but then the measuring electronics is measuring also wire resistance, which is not desirable.
Using extra wires for compensating the cable resistance gives more precisely the desired resistance of the RTD itself.
The 4 wires connection is the most accurate one.
Pt100 wire colors
Colors of wires attached to Pt100 resistance are defined in standard EN 60751.
For 2 wires, one resistance:
For 2 wires, two resistances:
For 2 wires, 3 resistances:
For 3 wires, one resistance:
For 3 wires, two resistances:
For 3 wires, three resistances:
For 4 wires, one resistance:
For 4 wires, two resistances: