ohm reading

[Mark-VA]

Need pin out ohm reading for the fisher f75 11" dd coil
Thanks

[Skippy]

I'm pretty sure the full L & R info are stated in another thread on here, but nevertheless:
Pin1 - Pin2 : R = 38 Ohms
Pin3 - Pin4 : R = 2.4 Ohms
Pin5 is connected to the screen/shield, and none of the other pins.

[Skippy]

Presumably your question is related to your earlier thread on the subject of F75 & T2 coils?
http://www.geotech1.com/forums/showt...75-5-quot-coil

It would've made sense to add your question onto that thread, rather than starting another thread.

I don't know if you have an inductance meter, but the F75 11" x 7" L readings are:
Pin1,2 : L = 6.95 millihenry (this is the receive coil)
Pin3,4 : L = 690 microhenry (the transmit coil)

[Mark-VA]

I have lost coil ohm information. What sparked me to ask was I recently purchase the ARC Pro version of the F75. I noticed the machine would false if I move the detector quickly or rather shook it in the air. Thought it might be a bad coil so I switched to the 5" and no issues with false chatter. Checked the pin ohm readings and was shocked to find pin 1-2 was .5 ohms, and knowing that seemed to very low for this coil. The 5" coil reads from pin 1-2 is 38.5 ohms. I'd guess something might be wrong. I'll run the detector through my test garden and that will add to my suspensions. I could almost guess someone might have put the wrong coil in the box.

[Skippy]

30 -50 Ohms is a common receive-coil resistance, so even if it's an 11x7 coil for a different First Texas machine, like a F19/Greek series, I would still expect similar R value. The exception would be the Fisher F4 coil, which DOES have a low resistance Receive coil, less than 2 Ohms, I recall. This is made to be compatible with the 'Bounty Hunter' concentric coils that the F2/F4 use.

I'm not sure about the 'shaking in the air' thing... it could be the ground pickup varying, and a false trigger as a result. My own machine will do that sometimes. Try shaking it horizontally, so it's still the same height above the ground, and all that occurs is shaking, with little pickup changes.

[Mark-VA]

Did extensive test and found the coil is most likely okay. Noise while shaking the coil only happens when disc is 0. As for the Ohm readings, I think one of my meter leads is failing. Test garden results were good. Thanks for all the input.