Time and Frequency Metrology Section

Our division is responsible for the highest level of time and frequency measurements in India and keeping them traceable to the International Bureau of Weights and Measures (BIPM) using ultraprecise satellite links. In simple words, we maintain the Indian Standard Time (IST). The time keeping by us is based on a bank of Cesium (Cs) atomic clocks and a Hydrogen maser. These clocks are so accurate that they would lose or gain one second in about three lakh years. The traceability of our time scale with BIPM is at the level of few nano-seconds (ns). In addition, we carry out research and development on primary atomic clocks.


The major activities in timekeeping at NPL comprise the following:

Time Generation and Dissemination

  • Generation and maintenance of UTC(NPLI)
  • Time transfer using GNSS
  • Time transfer using TWSTFT
  • Internet Time Dissemination Service (NTP Service)
  • Dissemination by Telephone Time broadcast (Teleclock, Fonoclock),.

Cs Fountain Frequency Standard

  • Frequency evaluation and international inter-comparison of the first Cs Fountain.
  • Development of the second Cs Fountain.

Rubidium Clocks for Space Applications

  • Filling up bulbs and cells with Rb.
  • Development of physics package of the clock.

Optical Frequency Standards

  • Development of single trapped Yb + ion standard.

Calibration Services

  • Atomic Clocks (Rb & Cs Freq Standards), Time Interval Counter, Hour Meter, Teleclocks, GPS timing receivers and Stopwatch.
  • Providing traceability to IRNSS time scale of ISRO.
  • Remote calibration set-up.




R&D on Primary standards of T&F

CSIR-NPL is perusing R&D activities on the development of modern primary reference clocks with improved accuracies (e.g. few-nanoseconds) at par with international standards .


 MOU was signed between CSIR-National Physical Laboratory and Department of Telecommunication

Memorandum of Understanding (MOU) signing ceremony jointly held by Department of Telecommunications, Ministry of Communications and CSIR-NPL, Ministry of Science & Technology on 25/04/2018, Wednesday atApex Metrology Building, Conference Hall , CSIR-National Physical Laboratory, Dr. K.S. Krishnan Marg, New Delhi



 MOU with ISRO

We are providing UTC Traceability to the Time scale of the Indian Regional Navigational Satellite System (IRNSS). This Time scale is known as the IRNWT and is maintained by the Indian Space Research Organization (ISRO). The technique used presently is all in view GPS P3. We supplement this with a dedicated TWSTFT link.



List of CMCs



Dr. Ashish Agarwal
Principal Scientist
Time & Frequency and Electrical & Electronics Metrology Division
Phone: 91-11-4560-8384 / 91-98-6880-6150
E-mail:  ashish@nplindia.org

Head, Time & Frequency and Electrical & Electronics Metrology Division
Room No. 126
National Physical Laboratory
Dr. K. S. Krishnan Marg
New Delhi – 110012