Frequency and time


The uncertainties quoted here are expanded uncertainties representing a confidence level of approximately 95 percent. They were obtained assuming a normal distribution and multiplying the standard uncertainty (one standard deviation) by a coverage factor of k=2.


NRC operates an atomic clock ensemble consisting of primary cesium beam time standards and commercial cesium clocks. These clocks operate on a continuous basis and produce the NRC time scale. In addition to these cesium clocks, NRC operates atomic hydrogen masers whose stable output frequencies are used in the evaluation of various standards.

NRC also maintains standards of optical frequency and vacuum wavelength to provide traceability to the SI metre. These standards include an ensemble of three 633-nm (visible red wavelength) helium-neon lasers stabilized on the 11-5 band R (127) component of iodine-127. The fractional uncertainty of the frequency of these lasers relative to the cesium standard is 5 x 10-11. For calibrations in the 1540 nm optical telecommunications band, NRC operates a diode laser system stabilized on transitions in acetylene. An optical frequency comb is used in periodic calibrations of these optical standards, as well as to provide calibration capabilities at other optical wavelengths.

Laboratory services

NRC performs in-house calibrations on a variety of instruments such as commercial cesium atomic frequency standards, rubidium frequency standards, quartz oscillators, signal generators, synthesizers, and electronic counters and timers. The frequency drift and frequency stability of a frequency standard can also be measured. The uncertainty of the calibration is usually limited only by the quality of the instrument submitted. The basic reference for the measurements is the primary cesium standard, which has an uncertainty as good as 1 x 10-13 relative to the SI second. Its frequency stability over one day is 10-14. Hydrogen masers provide a reference that has a stability as low as 10-15 over 1000 seconds. The indicated time of clocks brought to NRC can be related to time scales in other countries, usually with an uncertainty of less than 100 ns.

NRC maintains facilities for calibrating frequency-stable helium-neon lasers used in length metrology and scientific research. The absolute values of wavelengths of lasers are determined by comparing the laser frequencies against the primary standard laser frequencies. An ongoing research program in the development of new optical frequency standards provides many accurately known infrared laser frequencies that can be used as standards for laser frequency/wavelength calibrations. This service is available only by special arrangement and on an experimental basis.

Remote services

We assist clients in making traceable time and frequency comparisons with NRC. The comparisons are made on equipment at the client's site and can have uncertainties in frequency as low as 10-13. Clients can arrange service by contacting us. Comparisons are made via signals from GPS (global positioning service) satellites across Canada. NRC can also assist in comparing the frequency of a client's standard with the frequency of the time scales of other laboratories such as the Bureau International des Poids et Mesures, the Physikalisch Technische Bundesanstalt, and the National Institute of Standards and Technology.

Users can make frequency calibrations and obtain time of day information from a variety of time signals disseminated across Canada by NRC. Short wave radio station CHU broadcasts time signals at three frequencies: 3.33 MHz, 7.850 MHz, and 14.67 MHz, with a frequency uncertainty of 5 x 10-12 as transmitted. The time of day is available from a telephone signal provided by NRC to the CBC AM radio network and retransmitted daily at 13:00 Eastern Time in English and 12:00 Eastern Time in French. The time of day can also be obtained by dialing (613) 745-1576 for English, (613) 745-9426 for French, or (613) 745-3900 for computer readable code. These numbers are not toll free.

NRC TimeLinkTM – remote clock

The demand for secure and accurate time has been growing in recent years in telecommunications, infrastructure, navigation and finance, with these sectors requiring traceable time with sub micro-second precision. Currently available methods have technical or reliability limitations in achieving this goal, so NRC has developed a remote time system with uncertainty down to the nanosecond level. Based on a high quality local oscillator and GPS for time transfer, the remote clock is continuously monitored and adjusted to UTC (NRC) to ensure traceability, and minimize vulnerability to GPS signal jamming and spoofing.

For inquiries please contact:
Martin Rutter
Telephone: 613-990-6439

Fees for service

If you wish to order a calibration service, please request a quote from the following technical contact:

Telephone: 613-993-5186

Note that the calibration costs quoted DO NOT include shipping, insurance or the cost of a customs broker. The client must arrange and pay for these services separately.

Calibration number Description Fee
A33-07-00-00 Custom frequency or time standards measurements or services Fee on request
A33-07-00-01 Handling fee. A charge is levied for any instrument found to be unsuitable for calibration. This fee covers opening, inspection and return, and is based on the work done prior to discovery of the fault. $250
A33-07-00-02 Unsuitable instrument handling fee. Fee on request
A33-07-00-03 Special set-up handling fee. $150

Time measurements

Calibration number Description Fee
A33-07-01-01 Time measurement. This service measures the time of a portable clock, providing 1 pps (pulse per second) output to within 100 ns with respect to any international time scale or to within 2 ns of the NRC time scale. $510
A33-07-01-02 Time measurement and setting. This service measures and sets the time of an easily adjustable clock that provides a 1 pps output. $570

Time interval and frequency measurements

The uncertainty quoted in each of the following descriptions is for the specified measurement period under normal laboratory conditions only. Investigations of the effects of ambient temperature, other environmental factors or instrumental parameters are not included. The overall uncertainty depends on the stability of the standard under test both during the test and during transit to and from NRC.

Repeated measurements can be taken upon request. Additional fees are charged only to cover the added time required for the test and are generally significantly lower than for the original test. The calibration of equipment, which cannot be interfaced electronically with the measuring system, for example, stop-watches or oscillators with non-standard output, will generally cost more and produce much higher uncertainty than that shown below.

Calibration number Description Fee
A33-07-02-01 Counter-timers and synthesizers. Measurement is taken of the crystal oscillator frequency of frequency counter-timers and synthesizers to an uncertainty commensurate with the crystal quality, but not less than 5 x 10-9. $370
A33-07-02-02 Frequency measurement and setting (crystal oscillator). The measurement and setting of the crystal oscillator frequency of frequency counter-timers and synthesizers are determined to an uncertainty commensurate with the crystal quality and the ease of adjustment, but not less than 5 x 10-9. $450
A33-07-02-03 Frequency measurement (crystal frequency standard). The mean output frequency of a quartz crystal frequency standard is measured over a period of one hour to an uncertainty commensurate with the crystal quality, but not less than 1 x 10-11. $650
A33-07-02-04 Frequency measurement and setting (crystal frequency standard). The measurement and setting of the mean output frequency of a quartz crystal frequency standard are determined over a period of one hour to an uncertainty commensurate with its stability and re-setability, but not less than 1 x 10-11. $770
A33-07-02-05 Frequency measurement (rubidium or cesium frequency standard). The mean output frequency of a rubidium or cesium frequency standard is measured over a period of 24 hours to an uncertainty commensurate with its stability, but not less than 2 x 10-13. $905
A33-07-02-06 Frequency measurement and setting (rubidium or cesium frequency standard). The measurement and setting of the mean output frequency of a rubidium or cesium frequency standard are determined over a period of 24 hours to an uncertainty commensurate with its stability and re-setability, but not less than 2 x 10-13. $1,110

Frequency stability

For each service described below, the frequency stability is measured over the specified period and under normal laboratory conditions. It is preferable that the unit be operating on battery power when it is delivered to NRC. If this is not possible, a warm-up period should be specified indicating the length of time to wait after the unit is switched on at NRC before measurements can begin.

Calibration number Description Fee
A33-07-03-01 Measurement of crystal oscillator drift rate. The frequency and frequency drift of a quartz crystal frequency standard are measured over a period of one week to uncertainties commensurate with the crystal quality, but not less than 1 x 10-12 in frequency or 1 x 10-13/day in frequency drift. $1,095
A33-07-03-03 Customized measurement of Allan variance of frequency standard. Customized, shorter-term stability measurements of the Allan variance can be made over periods as short as one second for frequency standards with at 5 MHz output. Uncertainties of 2 x 10-15 can be obtained for time intervals of 1000 - 105 seconds. Fee on request
A33-07-03-04 Time and frequency traceability to NRC. Customized assistance is available for establishing time and frequency traceability to NRC using signals from GPS satellites, using the common view technique to overcome the effects of SA (selective availability). Fee on request

Laser frequency/wavelength

Calibration of helium-neon lasers at 633 nm

For information about laser frequency/wavelength calibration services, please visit Optical frequency/wavelength.

Authenticated NTP services

NRC offers NTP (network time protocol) servers with optional authentication procedures. Using authentication, a client's server can have assurance that the Internet data packets containing the NTP time stamp comes from NRC. Authentication is obtained by encrypting the data in MD5 (Message Digest 5) format. MD5 is restricted for use in Canada and the U.S. only.

At present, there is no fee for unauthenticated NTP time service. To receive authenticated NTP service, for a one-time fee, a client will receive a key code and a password on an NTP server at NRC. Authentication is available on our stratum-1 and stratum-2 servers.

The client must specify how many servers they will synchronize to, and whether each is stratum-1 or stratum-2. The client will specify how the keyID and password will initially be sent. They can be sent by telephone, fax, email or courier.

Calibration number Description Fee
A33-07-06-01 Time service, secure NTP, set-up fee. A one-time set-up fee will be charged for a key ID and a password on each server that will provide authenticated time service. This fee is valid for one client host installation. $125
A33-07-06-02 Time service, secure NTP, annual maintenance fee. A yearly fee, paid in advance, will be charged to maintain one authentication key for a client on one NRC NTP server. $125
A33-07-06-03 Time service, secure NTP, annual maintenance fee, extra server. A yearly fee, paid in advance, will be charged to maintain each additional authentication key for a client on another NRC NTP server. $75


Telephone: 613-993-5186

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