Question

What are the advantages of Wheatstone bridge measurement over a direct resistance measurement if for a temperature sensor?

Answer 1

lets first look at direct resiatance measurment

for this temperature sensor connected in series with a kown resisor (R)

by measuring the voltage across the sensor decide the resistance of sensor

since the R and sensor are in series by using voltage division rule

we find Voltage across sensor as

if you can observe clearly for small change of Rsen there would not be any change in Vsen so

we can not occuratly measure the temperature change.

but

in case of Wheatstone bridge, we design bridge circuit is in balance at some temperature (as per our requirment)

Bridge circuit is:

see Vout is taken across C and D terminals.

when bridge is in balance Vout = 0V

since all resistors other than Rx in nework are constant

if any small change in Rx the bridge will out of balanced condition

we can identify a significant change in Vout

hence using bridge we can measure even mV rage signls where as small chage is not recognized by direct resistance measurement.