First, I pulled the meter out and measured it, Red to Black = 305.4 Ω, Red to White(to tank wire) = 111.3Ω, Blank to White = 194.3Ω. The voltage out of the meter appears to be a voltage divider.
The attached is the schematic of what worked and after adjustments, the 2nd number by the pots is their setting.
In practice the "true opamp integrator" produced a 10 volt square wave, so I went back to an RC integrator.
Another fun little project,
Thanks for the help,
Kinarfi