Reference Standards and Calibration
Every measurement made in the Velocity Interoperability Network is traceable, through an unbroken chain of comparisons, to the reference standards of measurement held in the custody of the Department. The Department maintains the standards, compares them with one another and with the standards of the laboratories, and calibrates the instruments of member organisations against them.
Traceability is what allows a measurement made by one organisation to be relied on by another. The Department calibrates instruments at its Calibration Laboratory at Northgate Relay; chemical analysers are calibrated at the Analytical Chemistry Laboratory against primary reference materials. A certificate of calibration issued by the Department records the standard applied, the results at each point and the uncertainty of the comparison.
Calibration service opens on Monday 7 September 2026
The standards register. The register below records the reference standards in the Department's custody at establishment. Each standard is kept under controlled conditions by its custodian laboratory and is compared at least annually; artefacts are intercompared in pairs where two are held.
| Quantity | Standard held | Custodian laboratory | Uncertainty |
|---|---|---|---|
| Time and frequency | Caesium frequency standard | National Measurement Laboratory | 1 part in 10¹² |
| Length | Iodine-stabilised laser interferometer | National Measurement Laboratory | 2 parts in 100 million |
| Mass | Stainless-steel kilogram artefacts, Nos. 1 and 2 | National Measurement Laboratory | 0.05 milligrams |
| Temperature | Triple-point-of-water cells | Calibration Laboratory | 0.2 millikelvin |
| Electric potential | Solid-state voltage reference bank | Calibration Laboratory | 0.5 parts in 10⁶ |
| Mass fraction and purity | Primary reference materials | Analytical Chemistry Laboratory | Stated on each certificate |
The Department keeps the register under review. A standard is replaced when its condition or uncertainty no longer serves the measurements made against it, and the replacement is announced in the Newsroom.
Calibration services. The services below are provided to member organisations and to the departments of the Network. The stated turnaround is the usual period from receipt of an instrument to the issue of its certificate, and applies at establishment; it will be reviewed in the light of demand.
| Instrument group | Laboratory | Usual turnaround | Sessions or intakes |
|---|---|---|---|
| Balances and scales | Calibration Laboratory | 5 working days | Monthly |
| Dimensional instruments (callipers, micrometers, gauges) | Calibration Laboratory | 5 working days | Monthly |
| Thermometers and temperature probes | Calibration Laboratory | 10 working days | Monthly |
| Electrical instruments (meters, oscilloscopes) | Calibration Laboratory | 10 working days | Monthly |
| Pressure gauges and transducers | Calibration Laboratory | 10 working days | Fortnightly |
| Chemical analysers | Analytical Chemistry Laboratory | 15 working days | Quarterly |
Submitting an instrument for calibration. The steps below apply to every calibration submitted to the Department.
Step 1: Write to the Department
Send a description of each instrument, its owner organisation and site, the accuracy required and the date by which it is needed, to the Department's email address. The Department confirms within two working days whether the work can be undertaken and when.
Step 2: Send the instrument
Send the instrument to the Calibration Laboratory at Northgate Relay, marked with the submission reference issued by the Department. Instruments should be sent in their protective cases where they have them.
Step 3: The instrument is calibrated
The instrument is compared against the reference standard for its quantity, across the range of its use. Where an instrument is adjusted, the readings before and after adjustment are both recorded.
Step 4: The certificate is issued
A certificate of calibration is issued bearing the instrument's identification, the standard applied, the results at each point and the uncertainty of the comparison. Instruments are returned to the sending organisation with the certificate.
Organisations holding instruments that fall outside these groups may write to the Department, which will advise whether the instrument can be calibrated or should be referred elsewhere. Enquiries about the standards register may be sent to contact@science.gov.vin. For the work of the six laboratories, see National Laboratories; for the committees that advise on the standards, see Scientific Advice; for answers to common questions, see the frequently asked questions.