Capacitive displacement sensor is constructed of two plates

Capacitive displacement sensor is constructed of two plates, one fixed and one moveable as shown below. The parameters are indicated as in Figure 1. Assuming that you can measure the capacitance of the device(C), Y and d explain how you can use the device as a proximity sensor using the equations. Assuming that you can measure the capacitance of the device(C), Y and x explain how you can use the device as a proximity sensor using the equations

Solution

(a) C= €yx/d , where €= permitivity

X= Cd/(€y)

X= size of object can be measure

(b) d= €yx/C

d=Distance of object from fixed plate can be measure.

(B) R= resistance of potential meter at x degree rotation

=1.8x/210 k ohm

V= voltage across potentiometer=3.5*R/(R+0.5)

0.8=3.5R/(R+0.5)

R=0.8*0.3/2.7=0.8/9 k ohm

Hence X=R*210/1.8 = 10.37 degree

Rotation X= 10.37 degree