Question

A potentiometer displacement sensor is to be used to measure work piece motion from 0 to 100 cm. The resistance changes linearly over this range from \(0\ to \ 1 ~ k \Omega \). The above sensor is incorporated in the op-amp based signal conditioning circuit as shown below. For an input motion of 40 cm the voltage output (volt) of the op-amp is ?


Potentionmetric 15V (const) Sensor

• A. 4V
• B. 0.4V
• C. 40mV
• D. 4mV

Answer 1

The correct option is A 4V

Since the length varies linearly with resistance due to 40 cm the
resistance is:-

$\because 100cm\to 1k\Omega$

$40cm\to 0.4k\Omega$

$V_{out}=-\left(\frac{R_F}{R_1}\right)V_{in}$

$R_F=\text{Resistance of potentiometer}$

$R_1=1k\Omega$

$V_{in}=-10V$

$\therefore V_{out}=-\left(\frac{0.4k}{1k}\right)\times (-10)$

$V_{out}=4V$