Precision Timing for Reliable Power.  Simplified.
CM4000 Time Sync


DCF77 Protocol Description

DCF77 is a time synchronization protocol with its origin in Europe.  DCF77 was developed by the Physikalisch-Technische Bundesanstalt (PTB), the national institute for science and technology in Germany.   Historically, DCF77 has been used to synchronize power system devices, such as breakers, relays and meters, by Schneider Electric, Eaton and others.

DCF77 is typically distributed at 24V as a DC level shift (DCLS), pulse-width coded signal that provides a complete date/time string once every minute.  Like IRIG-B, DCF77 is used for time sync, accurate to 100 microseconds in reference to UTC (Coordinated Universal Time).

For more details on DCF77 protocol and its applications, see Tech Note: Overview of DCF77 Time Protocol (TN-103)


Time Sync: CM4000 Power Meters

Modern industrial/commercial power systems require precise time synchronization of all devices to ensure meaningful data for analysis and reliable operation.   CM4000 Circuit Monitors from Schneider Electric (as well as older CM3000 and PM800 meters) support DCF77 protocol for precision time sync.   CyTime™   SER-3200/2408 Sequence of Events Recorders from Cyber Sciences can generate DCF77 to synchronize these meters, greatly simplifying time sync design.   SER-3200/2408 Event Recorders accept a variety of time source options and then sync with each other using PTP.  In turn, a PTP slave can also output a legacy protocol (e.g., DCF77) to devices that do not support PTP (e.g., CM4000).

CM4000 Time Sync Wiring

A CM4000 (or CM4000T or CM3000 or PM800 series) can decode a DCF77 time sync signal via a dedicated digital input.   To take advantage of PTP (IEEE 1588) precision time sync over Ethernet, an SER-3200-PTP (or SER-2408-PTP) is configured as a time sync master with DCF77 as its output (via PLX-24V).

CM4000 Setup

When using DCF77 for time synchronization, CM4000 meters are configured for time sync via a dedicated digital input.  DCF77 can only be connected to one of the digital inputs located on the meter base, not an option module.   The device must be set as follows:

  • Input Mode = DCF77 (for the digital input wired to the IRIG-B signal)
  • Ensure the current year is set correctly prior to connecting the DCF77 signal.

For more details, see Tech Note: Overview of DCF77 Time Protocol (TN-103)