Installation Guide

8 Introduction
soft-start mechanism for the ECN system processor and expansion cards, and
prevents heavy loading on the power supply while line voltages are settling.
When the power supply is stable, reset is released and a “wake-up” interrupt is
issued to the measurement processor, which has been operating in watch mode
while power was off. During initialization, the measurement processor starts to
monitor the AC line voltage and begins its other measurement tasks.
Power-Down Function
While the ECN is operational, the measurement processor continually monitors
line voltages. When the line voltage drops below 50% of nominal for longer than
one minute, the system performs its power-down procedure:
• The system processor completes housekeeping tasks.
• If the ECN unit includes backup batteries, the ECN switches to battery
power.
• If the ECN unit does not include backup batteries, the main system
processor and all expansion cards are held in reset and the measurement
processor enters watch mode. In this mode, the real-time clock and
tamper functions are maintained.
For line voltage drops of less than one minute, the ECN operates in brown-out
mode, with internal capacitance providing temporary power to the ECN unit.
WARNING: Wait at least one minute after removing mains power from an ECN
unit before opening the cover and handling internal components, including
expansion cards.
Brown-Out Function
If the line voltage sags for longer than one second, but remains 50% to 80% of
nominal, the ECN runs in a reduced state of operation known as brown-out. In
this state, the ECN effectively operates as if it was in battery back-up mode, but
power continues to be taken from the line voltage, not the battery. The
measurement processor continues to monitor line voltage and hold the system in
brown-out state until power is either restored or removed.
Line voltage sags of less than one second are ignored and do not trigger a brown-
out event.
Energy Saving Mode
The ECN also provides a “Burst Mode Control” option. When in burst mode, the
power supply runs more efficiently. The burst mode circuit operates as a type of
relaxation oscillator where the output voltage from the power supply switches
between 11.8 V
DC
and 14.0 V
DC
. The burst mode operates when the temperature
is greater than 60 °C, thereby reducing the power dissipation inside the ECN
enclosure.
Peripheral Power Control
Power for the USB hubs and expansion cards is derived from the main power
supply on the ECN main system board. The hubs are powered by a single +5 V