resistances rtd

The principle of measure for resistances sensor is a variation a the resistance in function of the temperature. The Pt100 element is constituted / built in platinum and has a resistance of 100Ohms at 0°c following the certification iec, bs1904/jisc1604. The power measurement should not be over than 1mA to reduce the auto-heating sensor's risk.

2 cables assembly, measure by Wheatstone Bridge

2 cables assembly is the easiest assembly
Resistances r1 and r2 are on line with the measurement element.
The cable resistance (r1 + r2) is added to that of the element.


3 cables assembly, measure by Wheatstone Bridge

The 3 cable assembly is the most used. An equality of the resistances r1, r2, r3 is needed.
Contact resistances problems and drains bad balancing are still possibles.


4 cables assembly, measure by Wheatstone Bridge

In 4 cables assembly, two measures are done. Mistakes leaded by resistances of the two, two cables assembly are canceled. Moreover, both, line resistances and thermals drains balancing problems are solves. However, resistances contact remains.