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.


The 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, the NRC operates atomic hydrogen masers whose stable output frequencies are used in the evaluation of various standards.

The 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, the 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

The 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 1,000 seconds. The indicated time of clocks brought to the NRC can be related to time scales in other countries, usually with an uncertainty of less than 100 ns.

The 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.

NRC TimeLinkTM Services

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 the 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 to ensure traceability, and minimize vulnerability to GPS signal jamming and spoofing.

NRC TimeLinkTM - Monitored NTP

NRC TimeLinkTM - Monitored NTP services provide clients with a secure (authenticated) source of time directly traceable to UTC(NRC), the official time for Canada. Clients receive time synchronization through a connection with NRC stratum-1 servers and clients NTP server time accuracy is monitored by NRC systems. Monitored NTP clients receive monthly reports on their server's performance. These reports include the time accuracy of the client's server with uncertainties limited by the network's round trip delay and can be used for quality monitoring, auditing, as well as ensuring regulatory compliance. The NRC offers two tiers of Monitored NTP services with different levels of technical support, monitoring schedules and alerts.

Calibration number Description Fee
A33-07-04-01 NRC TimeLinkTM - Monitored NTP Basic. Service includes authenticated connection to stratum-1 NTP server, client NTP server performance monitoring, monthly reports, as well as basic, best effort customer support. Client server time offset from UTC(NRC) is measured to an uncertainty commensurate with the network delays but not less than 100 µs. This service does not include troubleshooting or remedial action. $1,500 per server per year
A33-07-04-02 NRC TimeLinkTM - Monitored NTP Premier. Service includes authenticated connection to stratum-1 NTP server, close monitoring of client NTP server performance, email alert/alarm notifications, monthly reports, as well as guaranteed 48 hour response time regarding customer support. Client server time offset from UTC(NRC) is measured to an uncertainty commensurate with the network delays but not less than 100 µs. This service will meet Investment Industry Regulatory Organization of Canada (IIROC) guidance on time synchronization requirements for traceability, alerting for time drifts beyond maximal allowable limits and audit trail requirements. $7,500 per server per year
A33-07-04-03 NRC TimeLinkTM - Remote Clock. This service provides a time of day signal, as well as a 1 pulse per second synchronized and traceable to UTC(NRC) with uncertainty better than 1 µs. Features such as long hold over times, monthly traceability reports and client PTP or NTP server performance monitoring and traceable measurements are available. Fee on request

For inquiries related to NRC TimeLinkTM services please contact:
Martin Rutter
Telephone: 613-990-6439

Authenticated NTP services

The 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 the NRC. Authenticated services are only offered in Canada and the U.S. as 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.

There is no fee for unmonitored NTP time services which are delivered via stratum-2 NTP servers. To receive authenticated NTP service, a client will need to request a key code and a password for an NTP server at the NRC.

The client must specify how many servers they will be synchronizing to NRC time. The client will select how the keyID and password can be communicated to them by NRC staff: via email or by telephone.

Remote services

Users can make frequency calibrations and obtain time of day information from a variety of time signals disseminated across Canada by the 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 the 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.

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 fees for measurement and calibration services are subject to change. The fees for service 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. $265

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 UTC time scale or to within 2 ns of the UTC(NRC) time scale. $540
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 with respect to UTC(NRC) time scale. $600

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 the 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 Stop watches and Timers. This service measures the device crystal oscillator frequency using the timer standard mode of operation as it would be used by the client. $620
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. Fee on request
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. $685
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. $810
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. $1,225
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. $1,410
A33-07-02-07A Counters and Tachometers. Measurements are taken of the crystal oscillator frequency to an uncertainty commensurate with the crystal quality, but not less than 5 x 10-9. This service includes a maximum of 4 frequency settings. $700
A33-07-02-07B Measurements of up to 4 additional frequency settings of A33-07-02-07A under the same conditions. $230

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 the 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 the NRC before measurements can begin.

Calibration number Description Fee
A33-07-03-01 Customized measurement and Allan deviation analysis of frequency standard stability including frequency drift evaluation. Stability analysis can be made for periods from one second to several days. 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.


Telephone: 613-993-5186

Date modified: