vary Precise Lc Meter

Posted on Feb 7, 2014

Well this is a Very Accurate LC Meter based on PIC 16F628A. Having inspired from surprisingly accurate LC Meter. This is my attempt to build an accurate L/C meter. This design is little different from other designs found on the internet. The goal of my hard work is to people get success in a single try. Cz Most of the design doesn`t

vary Precise Lc Meter
Click here to download the full size of the above Circuit.

work as described in the documentation or lack of information`s. The most challenging part of the project was to program the entire floating point math in 2k code memory of 16F628A. Basically LC meter is a kind of frequency meter, there is an LC Tank oscillator that oscillates with measured L or C and result is being calculated. The precision of frequency is up to 1Hz. For more details of measuring frequency with timers, see my article frequency counter. Theory of operation: Look at the schematic carefully; I didn`t use any reed relay, which is the burden for most of hobbyist, because of unavailability in local market. In my country (Bangladesh) it is also not available. So first I decided to use a Mosfet instead of Reed Relay. But I found better result in normal NPN transistor like BC547. If you don`t trust transistors, you can add Reed Relay yourself. I have used Pic`s internal comparator for oscillator and fed it to Timer1 External clock source to calculate frequency. So it eliminates the external Lm311 Op amp. The relay RL1 used for selecting L and C mode. The meter works on four basic equations. This are For both unknown L and C, Equation 1 and 2 are Common. Means we get F1 with internal LC tank circuit then connect Ccal Parallel with tank circuit and take the value of F2. After getting the raw value of inductance or capacitance, program automatically scales the value to engineering unites. Then shows it to 16x2 LCD...

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