Circuit's Blog :
Return to BlogDigital LC Meter with Accurate Measurment
Posted Feb 03, 2012 at 12:01 pm
Figure 1
The project is based on PIC16F628 and PIC16F84 microcontrollers to build an inductance/capacitance meter that can measure capacitance range from 0 to >0.1uF and inductance range from 0 to >10mH.
The project utilizes an LM311 comparator with positive feedback to make a parallel LC oscillator with digital output which seems to oscillate readily over a wide range of L and C values. The PIC program includes a test mode which is entered by shorting link LK1 and pressing zero to aid the initial troubleshooting. This will cause the PIC to repeatedly count oscillator cycles for 0.1 second and display the result. The oscillator will run at about 550KHz and the display will show around 55000 with just the 82uH inductor and 100pF in the circuit.
The display will show Over Range if the frequency is too high while the display will show 0 if the oscillator is not running. The free running frequency should be 10% to 15% below 655KHz for best accuracy. It may accidentally overflow the internal 16-bit count of the PIC if it is too close. This may require an adjustment of the inductance to get the right frequency.
Comments on this post:
Featured Products
Sullins Connectors
Wire-to-board interconnection options from Sullins feature a wide range of sizes and applications
MCC Voltage Suppressors
MCC’s TVS series high-power suppressors protect sensitive components from voltage spikes and transients
Bourns RS-485 Eval Boards
Evaluation boards that streamline evaluating circuit protection on RS-485 serial device ports
There are currently no comments.