Hi folks... I've been developing a homemade EMF meter with LED bargraph display, and am looking for some tips on tweaking the EMF sensing circuit.
I don't have a schematic for my actual circuit handy (circuit's at home, I'm at work), but it's based on this one:
**broken link removed**
But, if I disconnect the side of the coil going to the + input on the op amp in the schematic, leaving it free floating, then I can pick up fields. So, in essence, it's acting more as an antenna than an inductor. Any thoughts on this? Maybe I need a better coil?
My 2nd question: the circuit is a LOT more sensitive if I connect it to an earth ground, such as when I connect the grounding clip on my oscilloscope when taking readings. Any thoughts on this? Since I intend this device to be portable, I can't be earthing it all the time.
I'll post a more complete schematic this weekend when time permits, but thought I'd post what I have in case anyone has suggestions for making it better!
Thanks,
KJP