Thermometer circuit with temperature compensation

The circuit of a humidity measuring instrument with temperature compensation is shown in Figure 5-44
. When 0%.~100%RH, o-lov is output accordingly.
The output signal of IH-3605 is processed by the operational amplifier Al, so that at o%
RH, the output is ov (the voltage output by South RP1
is equal to the voltage output by 0% RH); at 25℃, the output of 100%RH
is iov . The Ptl00 platinum resistor is a temperature sensor, which is
amplified by the operational amplifier A2 and outputs a signal proportional to the temperature. Ptl00
and RP3 and two lOk resistors form a measuring bridge, and its working
voltage is provided by the op amp Al output to meet the compensation needs. A3
is an adder that adds the amplified humidity signal and the temperature compensation signal
(taken from RP4), and its output voltage is the temperature
compensated output voltage.