SATEC EM920 Operation Manual - Manual (Page 83)

Chapter 5 Configuring the EM920
General Meter Setup
EM920 Power Quality and Revenue Meter 83
Using the IRIG-B
Select the GPS IRIG-B option and connect the GPS master
clock to the meter IRIG-B input. See the EM920 Installation
Manual for the connection diagram.
The EM920 automatically synchronizes its clock with the GPS
time each second, normally with accuracy better than one
millisecond if the time is locked to the GPS satellite time.
When the GPS clock loses the satellite, the clock continues to
generate the IRIG-B time code referenced to the last
available satellite time (called unlocked time), but the time
quality may get worse. Such losses may continue from a few
minutes to hours. The time code generated during outages is
typically accurate to within a few milliseconds over a 24-hour
period.
If the signal from the GPS master clock is not detected on the
meter input, the EM920 changes the time synchronization
source to the internal RTC in 10 minutes after signal is lost.
When the signal is restored, the meter automatically acquires
the GPS time.
Whenever the IRIG-B signal status or quality changes, the
corresponding event is automatically recorded to the device
Event log.
You can check the presence and quality of the IRIG-B signal
via the device diagnostics display (see
Device Diagnostics
Display in Chapter 3) or via PAS (see Clearing Device
Diagnostics in Chapter 6).
Using SNTP
Enable SNTP client operation and configure it if required (see
Setting-Up SNTP Client ).
When an SNTP server is not available or when a connection
with a server is restored, the corresponding event is
automatically recorded to the device Event log.
Using Time Synchronization Pulses
Select one of the available digital inputs as either 1PPS, or
1PPM synchronization input.
The transition edge of an external pulse (open-to-close or
close-to-open transition depending on the selected pulse
polarity) adjusts the meter clock to the nearest whole second
for a 1PPS source, or to the nearest whole minute for a 1PPM
source. The time accuracy may be affected by the operation
delay of an external relay.