7.9. Reading without power (RWP)
The meter can be factory-fitted with an option that allows meter reading even when main network power is
missing. The power for this Reading Without Power (RWP) feature is provided by two dedicated (½ AA type)
batteries fitted in a holder located under the meter terminal cover, as shown:
The expected battery life is 10 years based on a typical usage cycle of 5 x 5minute readings a year.
The meter monitors the RWP battery voltage and raises a non-fatal alarm in the logbook when it falls below a
programmable threshold.
An RWP session is initialised by pushing the display pushbutton.
During an RWP session
There is no LCD back light and an RWP icon is lit on the meter display.
A meter reading can be taken immediately or after an EOB. An EOB action can be performed using the Reset
pushbutton (if enabled in configuration) or using the optical communication port. Only one EOB action can be
performed during an RWP session.
Certain alarms will be detected, typically:
Watchdog activity
External clock and programming incoherence
Excess demand - only when an EOB is done during the RWP session
Clock loss
RWP and RTC Battery low
Many meter functions are not available or inhibited, for example:
metrology (this is stopped, so there is no voltage measurement)
communication via serial ports
auxiliary I/O
most alarms
non-volatile memory save
DST management
The RWP session is closed automatically if no further action occurs during a programmable time out period.
Once the RWP session has ended, a programmable lock out interval prevents a successive RWP session from
being immediately initialised.
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