User Guide SL7000 IEC7
30
Alternatively, the APS also accepts an external DC voltage ranging from 48V to 145V.
Typical DC voltage APS terminal wiring illustrated below:
Note:
There is no polarization for DC APS (we can cVe on terminal 14 and –Ve on terminal 15.
6.4.
Power-fail operation
In the event of a continuous absence of power, all SL7000 meter data is saved in a non-volatile memory, with a
retention time of at least 10 years without the aid of any backup power.
The contents of the non-volatile memory are regularly checked with checksum markers and a fatal alarm (page
59) is raised if data corruption is detected.
6.5.
Real-time clock
The meter incorporates a Real-Time Clock (RTC) to facilitate time- and date-based energy rate switching,
interval measurement and time stamping of events.
The RTC can be configured to use either the mains supply or an integral quartz crystal as its default frequency
reference. Where the mains supply is used, the RTC will automatically be maintained during periods of power
failure by the quartz crystal powered from the meter's lithium battery or super-capacitor.
The quartz crystal is temperature-compensated to ensure accuracy over the operating range of the meter.
The meter can also be configured to synchronise the RTC against an externally-sourced control I/O signal, either
every hour or once a day.
The RTC meets the requirements for IEC 62052-21 and IEC 62054-21 time-switches for metering.
6.6.
Calendar
The calendar provides a flexible and configurable switching regime that handles up to sixteen energy rate
switches per day. The calendar also has the ability to apply different energy rate regimes during different
seasons of the year and on designated individual days.
Two completely separate calendar switching regimes are available and can be programmed into the meter:
•
Current
The switching regime currently in use by the meter.
•
Future
(latent)
An alternative switching regime that will be used by the meter once a pre-programmed due date is reached.
This feature accommodates any contractually agreed energy rate changes and automatically applies them when
they are due to come into force. At the due date, the future calendar becomes the current one; a further future
calendar can then be programmed into the meter.
