What are the Requirements for Calibration of Electrical Test Equipment in the UK?

In the UK, maintaining the accuracy and reliability of electrical test equipment is not just a matter of best practice but also a legal and safety requirement.

Calibration of electrical test equipment is essential to ensure that these instruments provide accurate readings, which is critical for the safety and compliance of electrical installations.

This article delves into the requirements for calibration of electrical test equipment in the UK, discussing its importance, the standards involved, and the process itself.

The Importance of Calibration

Calibration is the process of comparing the measurements from a piece of equipment against a standard known value.

In the field of electrical testing, the accuracy of instruments like multimeters, insulation testers, and RCD testers is crucial.

Incorrect readings can lead to a false sense of security, potentially overlooking dangerous faults in an electrical system.

Regular calibration ensures that these instruments perform accurately, safeguarding against electrical hazards, and ensuring compliance with industry standards.

Legal and Standard Requirements for Calibration

In the UK, the calibration of electrical test equipment is governed by various regulations and standards.

The Electricity at Work Regulations 1989, for instance, mandates that electrical systems be maintained to prevent danger.

This implicitly includes the need for accurate testing equipment.

Standards such as BS EN 61557 provide specifications for test equipment used in general electrical installations, emphasizing the need for regular calibration.

Frequency of Calibration

The frequency of calibration depends on various factors, including the manufacturer’s recommendations, the frequency of use, the environment in which the equipment is used, and the inherent stability of the equipment.

As a general rule, a yearly calibration is recommended for most electrical test equipment.

However, for equipment used more frequently or under harsh conditions, more frequent calibration may be necessary.

The Calibration Process

The calibration process involves several steps:

  1. Pre-Testing: The equipment is inspected for any signs of damage or wear that could affect its performance.
  2. Comparison with Standards: The readings from the equipment are compared against known standards. This usually involves using equipment that has a higher accuracy grade.
  3. Adjustment (if necessary): If discrepancies are found, the equipment may be adjusted to bring it back within acceptable accuracy limits.
  4. Certification and Documentation: After calibration, a certificate is issued detailing the equipment’s performance against the standards. This serves as a record of compliance and accuracy.

Choosing a Calibration Service

When selecting a calibration service, it’s important to choose a provider that is accredited by a recognised body, such as the United Kingdom Accreditation Service (UKAS).

Accredited calibration laboratories follow international standards, ensuring that the calibration is performed to the highest standards.

In-House vs External Calibration

Some organizations choose to perform calibration in-house, especially if they have a large number of equipment or require frequent calibrations.

This requires investment in calibration standards and trained personnel.

External calibration, on the other hand, is done by specialized laboratories and is often more practical for smaller operations or for equipment that requires less frequent calibration.

The Role of Calibration in Quality Assurance

Beyond compliance, calibration plays a critical role in quality assurance.

In industries where electrical measurements are critical, such as in inspection and testing, manufacturing or medical environments, the accuracy of electrical test equipment is paramount.

Calibration ensures that these measurements are reliable, supporting overall quality and safety standards.

GS38 and Requirements for Calibration

GS38, or ‘Guidance Note 38‘, is a set of guidelines issued by the Health and Safety Executive (HSE) in the UK, specifically targeting electrical testing.

This guidance is crucial for anyone involved in electrical testing, as it outlines the best practices to ensure safety.

Here’s what GS38 emphasizes:

  • Safety First: GS38 primarily focuses on safety measures to protect against electric shock and other hazards when using test equipment.
  • Equipment Standards: It specifies the standards that test probes, leads, and clips must meet. This includes aspects like insulation, durability, and ratings for voltage and current.
  • Regular Checks: The guidelines recommend regular visual inspections of testing equipment for any signs of damage or wear that could compromise safety or accuracy.
  • Best Practices: GS38 also advises on safe working practices, including the use of suitable protective gear and methods to minimize risks during electrical testing.

Adhering to GS38 not only ensures compliance with safety regulations but also boosts the reliability of test results by promoting the use of well-maintained, high-standard equipment.

The Importance of Quality Test Leads

The accuracy of your electrical test equipment heavily depends on the quality of your test leads. Here’s why good-quality test leads are non-negotiable:

  • Accurate Readings: High-quality leads ensure that the readings you get are as accurate as possible. Poorly made leads can introduce resistance, capacitance, or even noise, skewing your readings.
  • Reliability: Good leads are designed to withstand the rigours of regular use without breaking down, ensuring consistent performance over time.
  • Safety: Quality leads are usually better insulated and more durable, reducing the risk of electric shocks or shorts during testing.
  • Compliance with Standards: Quality leads are more likely to meet the stringent requirements set out in guidelines like GS38, ensuring that your testing practices are compliant and safe.

In conclusion, complying with GS38 guidelines and investing in high-quality test leads are both essential for accurate, safe, and reliable electrical testing.

These elements are fundamental in safeguarding against electrical hazards and ensuring the integrity of your testing procedures.

Remember, in the world of electrical testing, cutting corners on safety and equipment quality is never an option!


Calibration of electrical test equipment in the UK is a critical aspect of ensuring electrical safety and compliance.

By adhering to the legal requirements and standards, and ensuring regular and accurate calibration, businesses can maintain the safety of their electrical systems.

Whether conducted in-house or through accredited external services, calibration is an essential practice for any organization that relies on electrical test equipment.

The key takeaway is that the safety and effectiveness of electrical installations hinge significantly on the precision of the testing equipment, and regular calibration is the cornerstone of maintaining this precision.