Calibration vs. Function Testing: What UK Law (HSG47) Requires

↠Part of the Series: The 2026 Ultimate Guide to Cable Avoidance (CAT & Genny)

Calibration vs. Function Testing: What UK Law Actually Says

There is a dangerous misconception in the UK construction industry that pressing the "trigger" on a C.A.T4 constitutes a calibration check. It does not. As we move into 2026, with stricter adherence to HSG47 and insurance liability tightening, understanding the difference between a "Functional Check" and a "Calibration Certificate" is critical for every Site Manager and Surveyor.

In this guide, we strip away the jargon to explain exactly what is required to keep your kit legal, accurate, and safe.

Table of Contents

• The Legal Stance (HSG47 & PUWER)
• Daily Functional Checks: The Morning Routine
• Annual Calibration: The 12-Month Rule
• eCert & CALSafe: The Digital Revolution
• The Risks of Uncalibrated Equipment

The Legal Stance (HSG47 & PUWER)

The Health and Safety Executive (HSE) document HSG47: Avoiding Danger from Underground Services states that equipment must be "maintained in good working order." Furthermore, the Provision and Use of Work Equipment Regulations 1998 (PUWER) requires that all safety measurement equipment acts accurately.

If you have a utility strike and an investigation reveals your Locator was out of calibration (or had never been checked), your defence of "safe systems of work" collapses. Manufacturer guidelines (which H&S courts treat as the standard) typically mandate an annual calibration.

Daily Functional Checks: The Morning Routine

Every morning, before the C.A.T4 leaves the van, the operator must perform a Self-Test. This is not a calibration; it is a check that the circuitry is alive.

How to performing a Daily Check:

1. Hold the Trigger: On a C.A.T4, hold the trigger while switching the unit on.
2. Listen for the Tone: A single confirmed beep indicates the internal diagnostics (batteries, display, basic circuitry) are functioning.
3. Check the Genny: Turn on the Genny4. Does it emit a constant, strong tone? Does the induction boost work?
4. The "Swing" Test: Place the Genny on the ground in induction mode. Walk 5 metres away. Does the CAT pick it up? If you need to walk 2 metres to hear it, the sensitivity is drifting – Do Not Use It.

Annual Calibration: The 12-Month Rule

A functional check tells you the machine works. A calibration tells you the machine is accurate.

Over time, the delicate ferrite coils inside a locator can drift due to knocks, drops, and temperature changes. A unit might beep and look normal, but it could be reading a 1.0m deep cable as 1.5m deep a fatal margin of error.

The Bench Test: During an annual service, your unit is placed on a computer-controlled test rig. It tests:

• Frequency Lock: Is it listening to exactly 33kHz (or 131kHz), or has it drifted?
• Depth Accuracy: Is a 1.00m simulated signal reading as 1.00m?
• Gain Control: Does the sensitivity dial respond linearly?

Upon passing, a Calibration Certificate is issued. This is the document your Insurance Auditor will ask for.

eCert & CALSafe: The Digital Revolution

Managing paper certificates for a fleet of 50 locators is a nightmare. Radiodetection's eC.A.T4 and gC.A.T4 series solve this with two key features:

1. eCertâ„¢ (Remote Calibration)

Using the C.A.T Manager PC software, you can connect your locator via USB. The software runs a diagnostic test against the factory settings stored in the unit's firmware. If it passes, it extends the calibration validity for another year and prints a new certificate instantly. No downtime, no shipping costs.

2. CALSafeâ„¢ (Enforced Safety)

This is a setting for fleet managers who don't trust their teams to check dates. When enabled, the C.A.T4 will heavily restrict its functionality or simply refuse to work once the calibration date has passed. It forces compliance. A "dead" CAT is annoying; an uncalibrated CAT is dangerous.

The Risks of Uncalibrated Equipment

Using expired equipment isn't just about red tape. The physical risks include:

• Depth Errors: Drifting depth estimation leads to excavators digging aggressively when they should be hand-digging.
• Ghost Signals: Damaged coils can pick up "noise" from your own boots or mobile phone, masking the real utility signal.
• Reduced Sensitivity: A drifted unit might miss a weak telecoms signal that a calibrated unit would catch.

Conclusion

Calibration is your licence to operate. It proves that your "measurements" are fact, not fiction. Ensure every CAT and Genny in your fleet has a valid sticker, and if you have gC.A.T4s, utilize eCert to save thousands in service costs.

Need a service? View our Authorised Calibration Centre or upgrade to a gC.A.T4+ with eCert today.

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Why Professional Equipment Matters

In the field of utility surveying and safety, "cheap" equipment is arguably the most expensive mistake you can make. False readings leading to a cable strike, or a failed gas monitor in a sewer, can cost lives and millions in liability.

At Cable Locators & Survey, we stock only the verified industry standards Radiodetection, C.Scope, Abtech, and Leica. Every unit is checked, calibrated, and field-ready.