I wound a 18cm x 20cm RFID coil big enough for my cat go walk through with 55 turns of 30 gauge magnet wire. I measured the inductance with a cheapo meter to be 2.4 mH and the resistance as 15 Ohm. When I hooked it up to my RFID circuit it worked great and I got a detection range of about 6" with a standard fob.
Then I soaked the coil with super glue to keep the wires from moving and make the coil rigid. My RFID circuit quit working. I measured the inductance and it had changed to 1.6 mH and the resistance was still 15 Ohm.
Does anyone know what happened? I neglected to measure capacitance before. I didnt think cyanoacrylate was magnetic. I dont think it melted the magnet wire coating shorting out some wires as the coil resistance was unchanged. very strange.
I started winding another coil but ran out of wire. I will have to wait 3 days for more wire to come before I can wind another coil and measure capacitance.
Never mind. When the glue dried the inductance went back up.