Equipment Setup and Calibration Support
Reference electrodes
Copper-copper sulfate (CSE) is the field standard. Keep crystals visible in the solution, the porous plug wet and uncontaminated, and the tip clean; chloride contamination shifts the potential. Check a portable CSE against a second, stable electrode before and after a survey. A difference of about 5 mV or less is acceptable; larger differences require cleaning, re-soaking, or replacement. Ag/AgCl and zinc electrodes are used in specific environments, and the type must be recorded.
Meters and leads
Use a high-input-impedance voltmeter (10 MΩ minimum, 100 MΩ preferred) so electrode resistance does not load the circuit. Verify the meter against a certified source, check DC range selection, and confirm lead continuity and insulation before the first reading. Interrupters must be GPS-synchronized so instant-off readings are truly simultaneous; confirm synchronization, not just that the unit is running.
Shunts
Current is derived from a voltage drop across a known resistance: I = V/R. Record the shunt rating - mixing 0.001 Ω and 0.01 Ω shunts creates tenfold errors.
Traps: trusting a sticker instead of a verification check; using a low-impedance analog meter; a dry electrode giving a falsely positive reading. Worked example: a shunt rated 0.001 Ω shows 45 mV. I = 0.045 V / 0.001 Ω = 45 A. Reading that shunt as 0.01 Ω would wrongly report 4.5 A.