Follow the steps below to reduce current and voltage for very narrow pin/electrode spacings - ASTM G57, IEEE80, etc.
For very narrow spacing of 3, 2 or sometimes even 1/2 foot electrode spacing, operators will likely need to reduce the maximum current and possibly voltage allowed during auto-ranging of the higher power SuperSting™ instrument.
Manually Reducing Current:
Key sequence from the main menu
(6) System Settings
(1) Measurement Settings
(4) Output Current = 2000mA
(-) Several times to reduce current from 2000mA to 250mA or less
Enter to save new output current max
Press MEN key to return to the main menu
Continue test in manual mode
Additional step if needed to also reduce the output voltage:
(6) System Settings
(4) General Settings
(7) HVOLT=400
50V and press enter
With each voltage entered, the next nearest voltage bracket will be saved
The transmitter voltage range is 24 to 400V
Press MEN key to return to the main menu
Continue test in manual mode
For spacings above 5 feet, go back to defaults
Key sequence from the main menu
(6) System Settings
(4) General Settings
(4) Factory Defaults
Press MEN key to return to the main menu
Continue test in manual mode
The SuperSting™ produces a very strong DC pulse and resultant high signal to noise (S/N) compared to smaller handheld AC based testers. Lowering contact resistance is your primary control to further improve S/N as this allows more current to be injected. Raising the surface area of the stake also helps, but you need to limit pin/electrode size and penetration to avoid creating a line source vs the assumed point source. Inserting pins/electrodes to 10% or less of the a-spacing (pin/electrode separation) will maintain a point source and avoid artificially lowering the resistivity measured. If stability is an issue with narrow pins or dry soils try ~ 1 cup of 2% saltwater at the stake and soil interface to lower the contact resistance (ohm) without changing the resistivity (ohm-m) as sampled. This is suggested as a standard procedure to optimize data quality.