LC meter na PIC 16F628A

[SP6AN]

Witam.
Autor twierdzi, że nie są potrzebne dokładne elementy, lecz stabilne:

Special Components.

No particularly accurate components are required, except for one (or more) accurately known "external" capacitors used to calibrate the meter.
The two 1000pF capacitors ("C" and "Ccal") should be fairly good quality (stability is important, accuracy is not ;-). Polystyrene are preferred. MKT are fine, as are Mica. Greencaps tend to drift in value too much. Avoid ceramic capacitors. Some of these can have high losses (and it is hard to tell).
The two 10uF capacitors in the oscillator should be NEW tantalum ones (for low series resistance/inductance). Alternatively, "low ESR" aluminium capacitors can be used. You could add a 0.01uF ceramic capacitor in parallel with each, "just to be safe".
The 4MHz crystal should be a genuine 4.000MHz one, not something approximate to 4MHz. Every 1% error in crystal frequency adds 2% error to the indicated inductance value.
The 100uH inductor should have a low "DC" resistance. Ideally less than an Ohm or two.
The relay should be a low current one. The PIC can only provide about 30mA of drive current. The relay should be able to "pull in" with 4.5 volt applied to the coil. (Most 5volt reed relays will be OK).