PROBLEM FOR R18

[sisco]

HI Carl

I adjust r18 for maximum voltage TP4(~1.4 v) after this ,short pad 1 IC8

to ground and adjust r23 to voltage across pin2 and 3 IC8 for zero.

for readjust R18 i have problem.

in readjust R18 for zero TP4 i have noise in waveform.

you think this is a problem or not important.

I can't adjust better this picture.

[Carl-NC]

I suspect it's just interference... what do you have running at 33.33kHz?

[sisco]

I set R2 (with R3) TO Maximum frequency 2300Hz(2.99KHz).

but can't set R18 for Zero out with this noise.

other question:

what is best frequency for P1(positive and negative time of duty cycle )?

and with your HH for best setting any distance you can detect small coin(with

25cm dia coil)?

thank.

[Carl-NC]

In looking at your waveform, it appears to be picking up an 33.33kHz interferer. Try this...while probing TP4 rotate the coil to different angles between horizontal & vertical and see if the amplitude changes.

Best frequency for PI? I don't know... I run mine at ~1kHz, detects a US dime at ~6-7 inches as I recall.

- Carl