Using an oscillator running at 455 kHz, the metal-detector circuit produces an indication on the meter
Ml. When the oscillator frequency changes because of metal in the field of Li, the change will show as an
increase or decrease in frequency, which produces a charge iii the meter reading. The ceramic filter FILT1
produces a selective band pass that yields this effect. Li can be a 4” diameter coil wound on a suitable
plastic form. About 10 turns of #26 wire are required. Use a frequency counter to adjust Li and verify that
Q1 is operating on or near 455 kHz.
No comments:
Post a Comment