SATEC EM920 Operation Manual - Manual (Page 24)

Chapter 2 Operating the EM920
Operating Digital Inputs
24 EM920 Power Quality and Revenue Meter
Operating Digital Inputs
The EM920 can monitor a total of 10 digital inputs including
two fast internal digital inputs and 8 inputs found on the 8DI
expansion module. See the EM920 Installation Manual for
digital input ratings and connection diagrams.
Fast internal digital inputs are sampled at a 1-ms rate, and
expansion inputs are sampled at a 1/2-cycle rate.
Digital inputs functionality is programmable in the EM920 and
any digital input can perform multiple metering and control
functions at the same time:
• Receiving energy pulses from external watt meters
(sub metering) – link a digital input to a Billing/TOU
register and provide a required multiplication factor
(see
Configuring Billing/Tariff Registers in Chapter 5)
• Counting pulses from external pulse sources – link a
digital input to a pulse counter (see Using Counters in
Chapter 5)
• Triggering a setpoint – put a digital input into a
setpoint trigger list (see Using Control Setpoints in
Chapter 5)
• Triggering the Fault Recorder – link a digital input to
the Fault Recorder (see Configuring Digital Inputs in
Chapter 5) and enable external triggers in the Fault
Recorder setup (see
Configuring the Fault Recorder in
Chapter 5)
• External synchronization of power demand intervals –
select a digital input as an external power demand
sync source (see
Basic Meter Setup in Chapter 5)
• External synchronization of the meter clock – select a
digital input as a time synchronization input (see Local
Settings in Chapter 5) and provide 1PPS or 1PPM
pulses from the external master clock source.
All digital inputs have a user-programmable debounce time
from one to 100 milliseconds. See
Configuring Digital Inputs
in Chapter 5 on how to configure digital inputs in your meter.
Operating Relay Outputs
Up to seven relay outputs can be provided in your EM920
including one on-board KYZ relay output and six additional
outputs on the 6RO expansion module. See the EM920
Installation Manual for available relay output ratings and
connections.
All relay outputs are updated at a half-cycle rate.
Each relay is independently programmable in the EM920 and
can operate in latched, unlatched, pulse or KYZ mode.
Relay operations can be inverted so that the relay is
energized in its non-active state and de-energized when it is
operated. This mode, known as “failsafe” mode, may be used
for signaling purposes to send alarms when the device is not
operational either due to a fault or due to loss of power.