RTD 3th wire compensation Vs 2-wire with instrument amplifie

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Hermano Canguro

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Some one know why 3-wire RTD are broad used
instead just 2 wire with instrument amplifier ? any mathematical
analisys to get a clue ?

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Re: RTD 3th wire compensation Vs 2-wire with instrument ampl

third wire is used for earthing purpose for safty reasons.
 

Re: RTD 3th wire compensation Vs 2-wire with instrument ampl

Third wire is used for compensation of lead wire resistance. Since, the temperature resistance is interpreted by resistance
 
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    kender

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any mathematical analisys to get a clue ?
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It's simple enough to figure it out yourself, I think. 3-wire compensation is based on the assumption of equal resistance of both current carrying lead wires. It can't handle e.g. arbitrary contact resistances which would be compensated by a 4-wire circuit, too. For the analysis, simply assume a sensor resistance, wire resistances and a current source feeding the circuit.
 

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