Ground test probe spacing calculator

Preliminary estimate

Inputs

Calculation note

This estimates a probe layout distance only. Soil conditions, electrode geometry, test method, and instrument instructions govern field testing.

Method

Voltage probe distance = current probe distance x voltage probe percent / 100

Remaining distance = current probe distance - voltage probe distance

Total lead length estimate = current probe distance + voltage probe distance + electrode offset

MoreLess

Formula variables

  • Current probe distance is the entered distance from the electrode under test.
  • Voltage probe percent sets the voltage-probe placement along that distance.
  • Electrode offset is an optional extra lead allowance.
  • Total lead length is a setup planning estimate.

Assumptions

  • The calculator only places probes along the entered test line.
  • The voltage-probe percent is entered by the user, with 62 percent as the default shortcut.
  • Soil conditions, electrode geometry, and instrument method can invalidate a simple spacing layout.
  • This calculator does not set pass or fail targets, approve grounding systems, or replace instrument instructions.

Examples

62 percent setup. With a 30 m current-probe distance, a 62 percent voltage-probe point is 18.6 m from the electrode.

Test workflow. Use instrument instructions and site conditions before relying on a simplified probe layout.