PHYS345 Electricity and Electronics

Answer for P8-17

Av = V2/Vt =(10 V)/(42 mV) = 238 = 47.5dB.

Gain of 238 on an input offset of 5 mV yields an output offset of 1.2 V.

(42+5)/45 = 1.12, so the input offset makes the thermocouple emf look 12% higher than it actually is, thus the perceived temperature is 12% higher than 1000 deg; that is, 120 deg of error.

Changes in gain amplify the thermocouple emf and the input offset in the same proportion, so no minimization of input offset is accomplished by reducing the gain.

Last updated Oct. 30, 1998.
Copyright George Watson, Univ. of Delaware, 1998.