Experiment: Op amp applications

Purpose: This time we use the AS35 which the amplifier change its gain from its temperture connect to the Lm741 circuit, and it has the change scale factor of 10mV/ ºC. We should build the circuit and measure the Vc, VF, and Vref to get the relation of these value. Then calculating temperture with the formula.

The Lm741 part is the difference circuit
so the vf=(1+R2/R1)vc -(R2/R1)*Vref
The formula covert ºF to ºC is ºF=1.8ºC+32
If we assume the 1+R2/R1=1.8, the R2/R1 will be 0.8.
Then make -(R2/R1)*Vref=0.32, so the Vref= -0.4V
The relation of vf, vc, and vref will be the formula of temperture covert.

Data measures:
R1=2.12kΩ
R2=1.75kΩ,  R1/R2=0.825.
Vref=-0.404V
Vc=0.237V
Vf=0.765V

Calculation:
Tf= (1.825*0.24+0..825*0.404)*100=76.58ºF
The room temperture is 23ºC= 73.4ºF
error %=(76.58-73.4)/73.4=4.33%