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Sensor Installation Handbook Preface 3rd edition - Siemens ...

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Electrical resistance sensors<br />

Metals change their resistance (measure in ohms) with a change in<br />

temperature.<br />

The change in resistance per Kelvin (K) is different for every metal,<br />

and is used directly as an output signal.<br />

Material Construction Function System<br />

Platinum Electrical<br />

Nickel resistance, R,<br />

in ohms Ω<br />

There are two types of change in resistance:<br />

PTC: Positive temperature coefficient<br />

Rising temperature = increased resistance<br />

Falling temperature = reduced resistance<br />

NTC: Negative temperature coefficient<br />

Rising temperature = reduced resistance<br />

Falling temperature = increased resistance<br />

Temperature<br />

69

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