Linear variable differential transformers (LVDT) used to measure the displacement . Here output voltage will change according to the movement of core. It requires an alternating signal to excite the primary coil. It have found in variety of applications in industry to measure the displacement. A LVDT is basically an electro-mechanical transducer. In simpler words it is a transformer. Here the moving core is made by using ferrite. Ferrite has high magnetic permeability compared to air.
Reactance of inductor is given by,
XL=2πfL
From above equation its clear that we must chose high frequency above 100 KHz alternating wave
to increase the reactance in primary side. As a result low driving current
needed to drive primary coil. Here driving is done by half-bridge configuration
(L293D).H-Bridge configuration chosen because the wave to primary side is an alternating square wave.
In output side rectification and filtering is done to
obtain pure dc to interface with Micro-controller.
Simple half wave rectifier using germanium diode is used to reduce the voltage drop after rectification.
It has the following specifications:
• Linear range: ±12mm
• Sensitivity: 100mV/mm
Construction & working
The transducer construction consists of a cylindrical
transformer, with a single primary winding and Secondary winding. At one side
of hollow tube primary winding are made and on other side secondary winding are
made. Core made of ferrite core in shape of a cylinder. In primary winding,
high frequency square wave to excite the coil. Output is taken from Secondary
windings, which is rectified and filtered to obtain D.C. voltage
Materials Required
Final assembled part
Materials Required
Final assembled part
Output wave across the pin RC0 and RC1
Program
#include<pic.h>
#define _XTAL_FREQ 16000000__CONFIG(0X3F7A);
void main()
{
TRISC=0;
PORTC=0x01;
while(1)
{
PORTB=~PORTB;
}
}
