Satec Expertmeter EM720 Operation Manual page 74

Chapter 5 Configuring the EM720
74
beginning of the minute. If the IRIG-B option is selected
but the IRIG-B signal is not present on the device input,
the EM720 automatically uses its internal RTC clock.
Using the IRIG-B
To use the IRIG-B input, select the GPS IRIG-B option and
connect the GPS master clock to the IRIG-B BNC
connector on the IRIG-B communication module.
When the IRIG-B signal is present on the device input, the
EM720 automatically synchronizes the clock with the GPS
time each second, normally with accuracy better than 1
millisecond if the time is locked to the GPS satellite time.
If the GPS clock loses the satellite signal, the clock
continues to generate the IRIG-B time code referenced to
the last available satellite time, but the time quality may
get worse. Such signal losses can last from a few minutes
to hours. During such outages the time code generated by
the GPS receiver is typically accurate to within a few
milliseconds over a 24-hour period.
If the IRIG-B signal is lost, the EM720 changes the time
synchronization source to the internal RTC in 10 minutes.
When the IRIG-B
automatically acquires the GPS time.
Whenever the IRIG-B signal is lost or time code quality
changes (locked to the GPS satellite time or unlocked), the
corresponding event is automatically recorded to the
device Event log.
The lost or unlocked signal status is indicated in the device
diagnostics, so you can check presence and quality of the
IRIG-B signal via the device diagnostics display (see
Device Diagnostics Display
Clearing Device Diagnostics
Using Time Synchronization Pulses
External time synchronization pulses can be delivered
through one of the digital inputs. If a digital input is
selected as the time synchronization source, the edge of
an external pulse adjusts the device clock at the nearest
whole minute. The time accuracy could be affected by the
debounce time of the digital input, and by the operation
delay of the external relay.
EM720 Power Quality and Revenue Meter
General Meter Setup
signal is restored,
in Chapter 3) or via PAS (see
in Chapter 6).
the meter