Wheatstone Bridge
Wheatstone Bridge
Wheatstone Bridge
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Example<br />
Consider using a <strong>Wheatstone</strong> bridge having R 1 = 200 Ω and R 2 = 2000 Ω to measure a<br />
resistance, R m , of a temperature sensor. Suppose the resistance of the temperature sensor, R m ,<br />
in Ω, is related to the temperature T, in °C, by the equation<br />
R = 1500 + 25T<br />
m<br />
The temperature is expected to vary over the range 0 to 100 °C. Over what range must R 3 vary<br />
in order for the bridge to measure temperature over the range 0 to 100 °C?<br />
Solution:<br />
Solve equation 6 for R 3 :<br />
When T = 0 °C, Ω and 1500 R =<br />
m<br />
When T = 100 °C, ( )<br />
m<br />
2<br />
R1<br />
R3 = Rm<br />
(7)<br />
R<br />
R1<br />
200<br />
R3= Rm=<br />
1500 = 150 Ω<br />
R 2000<br />
R = 1500 + 25 100 = 4000 Ω and<br />
R1<br />
200<br />
R3= Rm=<br />
4000 = 400 Ω<br />
R 2000<br />
2<br />
R 3 could be implemented as a 150 Ω resistor in series with a 250 Ω potentiometer:<br />
2<br />
3
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