What is Calibration and Do I need it?

Calibration is the process of comparing an instrument’s measurements against a known reference to identify any inaccuracy. It ensures your equipment is measuring correctly and can often include adjustments to bring the readings back into specification.

Put simply, calibration confirms that what your instrument says is actually true.

• Accurate Measurements
  Instruments can drift over time due to regular use, environmental factors, or mechanical wear. Calibration restores accuracy and reliability.
• Compliance with Industry Standards
  Many industries require regular calibration to comply with regulations and quality standards such as ISO 9001 or ISO/IEC 17025.
• Traceability and Audit Readiness
  A calibration certificate provides traceability to national or international standards—important for audits, quality assurance, and certification.
• Cost Efficiency
  Reducing rework, product defects, and safety issues saves money. Calibration is a low-cost way to protect your reputation and operations.

The International Organisation for Standardisation (ISO) develops globally recognised standards that promote safety, quality, and consistency across industries. Two key ISO standards relevant to calibration include:

• ISO 9001 – Focuses on quality management systems. Calibration is often required as part of ongoing quality assurance.
• ISO/IEC 17025 – Applies specifically to calibration and testing laboratories. It ensures labs are technically competent and able to produce valid, reliable results.

Choosing calibration services that are compliant with ISO standards—especially ISO/IEC 17025—gives you confidence in the accuracy and traceability of your instruments.

There are several types of calibration available, depending on the level of assurance and traceability you require:

• Manufacturer Traceable Calibration - Also known as standard or factory calibration. This type of calibration compares your instrument to reference equipment that is traceable to national standards. It provides a calibration certificate but does not carry ISO/IEC 17025 accreditation.
  • Best for: Non-regulated industries, routine checks, internal quality systems.

• UKAS Accredited Calibration - Performed by a laboratory accredited by the United Kingdom Accreditation Service (UKAS) to ISO/IEC 17025. This type of calibration is highly reliable and comes with a certificate recognised internationally.
  • Best for: Regulated industries (e.g. medical, food, aerospace), critical measurements, ISO compliance.

• On-site Calibration - Some instruments can be calibrated at your premises, minimising downtime. This can be traceable or UKAS-accredited, depending on provider capability.
  • Best for: Fixed installations, high-use instruments, minimal disruption.

• In-house Calibration - For companies with their own reference standards and qualified personnel. Requires investment in training and equipment but offers immediate control.
  • Best for: High-volume users, large manufacturing environments.

The right calibration service depends on:

• Industry Requirements
  If you're in a regulated industry (e.g. healthcare, pharmaceuticals, aerospace), UKAS-accredited calibration is often mandatory.
• Purpose of Measurement
  For critical or safety-related measurements, use UKAS calibration. For trend monitoring or general use, traceable calibration may be sufficient.
• Audit or Certification Needs
  If you’re working towards or maintaining ISO certification, ensure your calibration provider offers documentation traceable to international standards.
• Budget and Frequency
  For routine use, traceable calibration is cost-effective and reliable. For high-accuracy needs, investing in accredited calibration is worthwhile.

There’s no one-size-fits-all answer, but general guidelines include:

• Annually – A good standard for most applications.
• Biannually or Quarterly – For critical equipment or harsh environments.
• Manufacturer Guidelines – Always follow these for specific instruments.
• After Repairs or Relocation – If an instrument has been moved, dropped or serviced, it should be recalibrated.

• Initial Inspection – Instrument is checked for physical damage or defects.
• Reference Comparison – Measurements are taken and compared to certified standards.
• Recording of ‘As-Found’ Data – Pre-adjustment readings are documented.
• Adjustment (if possible) – Instrument is fine-tuned to meet tolerance levels.
• ‘As-Left’ Verification – Post-adjustment readings are recorded.
• Certificate Issued – Complete with calibration results, uncertainties, and traceability.

Most calibrations are completed within 2–3 weeks of receipt. UKAS-accredited services may take slightly longer due to rigorous testing and documentation.

Whether you’re measuring temperature, humidity, pressure, or electrical signals, regular calibration is essential to keep your instruments accurate, compliant, and ready for audit.

ATP Instrumentation provides both traceable and UKAS-accredited calibration services, backed by decades of expertise. We help businesses across the UK meet quality standards with precision, confidence, and minimal downtime.