Capacitance Meter

[Meisam]

I want to design a Capacitance Meter with the use of Bridge Circuit.I need some help in designing a variable Capacitor for automatic balancing of the Bridge circuit.

 

[Nigel Goodwin]

I want to design a Capacitance Meter with the use of Bridge Circuit.I need some help in designing a variable Capacitor for automatic balancing of the Bridge circuit.

You vary the resistor, it's FAR easier, and just have switched capacitors to change ranges.

 

[Meisam]

Actually I want to measure the Telephone Likne resistance with calculation of TIP&RING Capacitance.
I found out that the best circuit for measuring Capacitance of TIP&RING is Bridge Circuit.
My problem is how can I make the Bridge circuit into balanced state by changing variable Capacitor or resistor.
Also I should mention that balancing should be done automatically by CPU.

 

[Nigel Goodwin]

Actually I want to measure the Telephone Likne resistance with calculation of TIP&RING Capacitance.
I found out that the best circuit for measuring Capacitance of TIP&RING is Bridge Circuit.
My problem is how can I make the Bridge circuit into balanced state by changing variable Capacitor or resistor.
Also I should mention that balancing should be done automatically by CPU.

I suggest you try googling for "wheatstone bridge", there's plenty of information out there.

To do it via a CPU try replacing the variable resistor with a digital resistor or poteniometer.