Time Synchronization

Purpose of Time Synchronization

When data is recorded and timestamped on board field devices, it is important to ensure that their internal clocks are accurate with respect to other devices and local time. The setting of devices to a single time reference is called time synchronization.

Time Synchronization Protocols

Various protocols and methodologies may be used to implement time synchronization.

Some of the most expensive, but most accurate time synchronization technologies rely on non-Ethernet protocols (for example IRIG-B, DCF77) linked to a GPS antenna, GPS receiver, and clock.

Ethernet-based protocols provide more economical solutions. The most cost-effective but less accurate approach is achieved with Modbus-based (or ION-based) time synchronization over an Ethernet or serial communications network.

Protocols such as NTP/SNTP are now commonly supported by a wide range of connected devices and can provide sufficient performances for non-critical applications, typically in the range of 1 s down to 10 ms, at an affordable cost.

A recent Ethernet-based protocol called PTP (Precision Time Protocol), defined in IEEE 1588 and IEC 61588, can achieve even more accurate time synchronization, in the range of 1 ms or better, offering a strong alternative to serial line based protocols.

	How to Optimize Time-Synchronization and Data Recording for EcoStruxure Power Digital Applications
	Technical Guide Ref: ESXP2TG001EN 11/2019