Trifield TF2. I found a used one on ebay for half price
Discussion
The magnetic sensor is pretty good on this one
But the RF and electric sensors suck pretty badly
Ideally you would get a Safe & Sound Pro2 (or CLASSIC thats cheaper) to properly measure RF
Electric is the least problematic of the 3, so if you cant measure that one super well its not a huge deal
Well that sucks 😕