Measure the Temperature of the RTD

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Suppose you need to measure the temperature of an operating oven using nothing but a 1000 Ω RTD (α = 0.00385), a 1.75 kΩ precision resistor, and a battery of unknown voltage:

measure the temperature of RTD

Turning the switch on, you measure 1.32 volts across the resistor and 1.22 volts across the RTD.

Calculate the oven temperature based on these measurements, and also explain why it is important to quickly take these measurements once the switch is turned on.

Answer :

RRTD = 1.617 kΩ

Toven = 160.4 oC = 320.7 oF (calculated from formula, not from a table)

The voltage measurements must be taken very soon after the switch is thrown to avoid measurement errors due to “self-heating” of the RTD.

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