Why Cable Locator Calibration Matters

A cable locator should be calibrated at least once a year. Calibration confirms the unit still responds at the correct sensitivity and depth accuracy. Because a locator drifts silently, an out-of-calibration CAT can read "clear" over a live cable, which is the exact failure that calibration exists to prevent.

Calibration is the least glamorous part of cable avoidance and the part that quietly keeps people alive. Here is why it matters and what a proper service involves.

Why does a locator need calibrating at all?

A CAT measures tiny electromagnetic fields. Over months of site use, components age, knocks accumulate, and the unit's response shifts. None of this is visible on the display. A drifted unit might under-read a shallow cable or over-read a harmless one. Annual calibration measures the unit against a known reference and brings it back to specification, so the number on the screen means what it should.

How often, and who says so?

Twelve months is the industry standard and the interval most fleet policies enforce. Many modern units include a CALSafe feature that can lock the CAT once calibration is overdue, which removes the temptation to keep using a lapsed unit. Network Rail and most major contractors will not let an uncalibrated locator on site.

What does a calibration service actually check?

• Sensitivity in Power, Radio and Genny modes against a reference signal.
• Depth accuracy on depth-capable models such as the CAT4+.
• Genny output and signal integrity.
• Physical condition, seals, batteries and connectors.

You should receive a calibration certificate confirming the unit met specification, with the date and the next due date. That certificate is your audit trail.

Calibration is not the same as a daily check

The annual calibration is the formal reference check. It does not replace the daily function check you do before each shift, where you confirm the unit powers up, self-tests and responds to a known signal. Both matter: the daily check catches sudden faults, the annual calibration catches slow drift.

Keeping a fleet compliant

If you run several units, stagger their calibration dates so you are never without kit, and keep certificates together for audits. We offer accredited CAT, Genny, gas and survey equipment calibration, service and repair, and we can turn units around quickly to keep you working. For the wider picture, see the 2026 ultimate guide to cable avoidance.