Time and frequency metrology

Time and frequency are factors used in all sorts of industrial processes, systems and sectors. The degree of accuracy of a timekeeping or positioning device is crucial. Reliable measurements and calibrations are directly traceable to the national time standard.


Time and frequency

Time is perhaps the most telling example of the importance of accurate and traceable measurement. Everyone has at some point missed a train or bus by just seconds. In an ice-skating competition, the difference between winning and losing is sometimes no more than a hundredth of a second. GPS positioning requires even more accurate timekeeping.

Time and frequency are quantities we apply in all sorts of industrial processes, data security systems, telecommunications, astronomy, geodesy, navigation and medical research. In stock market trading, the timestamp of a transaction directly affects the price the buyer or seller pays or receives.

Would you like to know more about our services?

Our experts are happy to help.

Michel Brakel
Sales Engineer

VSL and time and frequency

VSL is an expert in performing highly accurate and traceable measurements. We provide various time and frequency measurement services to clients including manufacturers and suppliers of frequency and time measuring instruments, research institutes, the Ministry of Defence, banks, telecom and Internet providers. We are also working in several research projects at European level, including one that is exploring whether the existing fibre optics network can be used to distribute very precise and stable signals.

VSL uses four atomic clocks to realise the Dutch national time standard. This standard is part of a global network that is used to collectively define the international time scale (or Coordinated Universal Time, (UTC)) and the duration of one second. This is done with a minimum uncertainty of 1 ns. VSL uses frequency dividers and multipliers, which create an extended frequency range. To compare time over long distances, VSL developed the Two Way Satellite Time and Frequency Transfer method (TWSTFT), which is applied internationally.


We support and advise manufacturers and end users with regard to questions, enabling them to improve measurement and inspection methods to optimise the quality of their processes and products.

Custom services

Custom time and frequency metrology

Organisations regularly request our expertise in time and frequency measurement. We work for a variety of companies and organisations, including the aerospace industry and financial institutions.

Our extensive knowledge of measurements and the interpretation of measurement data enables us to provide the following and other services:

  • Delay measurements using a satellite simulator.
  • Timestamping for financial institutions, for example.
  • Design and composition of measurement systems. From the design of measurement setups to traceability and construction.
  • Development and validation of measurement methods. This results in a report describing the measurement and validation method, including the determination of measurement uncertainty.

Every situation is unique. Do you need advice or would you like to know what we can do for you? Don’t hesitate to contact us.


Time and frequency calibration services

VSL provides the Netherlands’ most accurate time and frequency calibrations, which are directly traceable to the national time standard. VSL’s scope ranges from frequency measurements with an uncertainty of 0.000 000 000 000 2 Hz/Hz to stopwatch calibrations with an uncertainty of 0.014 seconds per day. Internationally respected and recognised, VSL’s calibration reports ensure that products are accepted worldwide.

Calibration of time and frequency measuring instruments

Measuring instruments need to be calibrated regularly to ensure accurate and traceable measurements of time and frequency. VSL calibrates stopwatches, clocks, oscilloscopes and other instruments.

Time Service Bulletin and time synchronisation

VSL’s weekly “Time Service Bulletin” provides information on signals whose time or phase difference from UTC (which is also the national time standard) has been measured. It also contains information from the IERS and BIPM. The Time Service Bulletin is available on subscription. Computers, however, can be time-synchronised free of charge through ntp.vsl.nl.

Our areas of expertise