NTC/humidity sensor Simulation help needed

Thread Starter


Joined Jan 17, 2016
Hello Guys,
I am struggling to simulate and understand below circuit but unable to understand it.
Could anyone help me out ?

Circuit Explanation -

In place of R6, R5 i have to use humidity sensor. So i consider it 56 ohm resistor.
R3, R4 is bridge resistance.

My circuit understanding is - 1658675796827.pngU2 is differential amplifier with gain of R9/R8.
I do not know how U1 is working without any feedback component.

Could any one help me to understand this circuit ?
Ltspice file is attached herewith.



Thread Starter


Joined Jan 17, 2016
Do you have the spec of the sensor? Does it act simply as a passive resistor or as an active voltage (or current) generator?
Hey Alec_t,

to be very frank no idea about humidity sensor.
It might be resistive.

Thanks for your support.