Operation Techniques
71
below analog output operation). The user should explicitly configure the status
inputs to be used as an analog output selector.
Pulse Inputs
The input pulse is recognized by the instrument at the negative input transition: open
⇒
closed. To be latched by the instrument, the pulse width should not be less than 50
ms. The minimum pause allowed between successive pulses is 50
ms.
Signals from pulse inputs are held by the instrument and buffered for three types of
applications, programmed by the user.
First, each pulse input can be connected to any of the 8 large-scale counters (see
below counter operation) to count pulses with arbitrary scaling, and concurrently -
to any of the 8 accumulating energy registers to count pulses from external energy-
counting meters (see
Section 4.7.5
).
Second, each incoming pulse is asserted as external event, and can trigger a setpoint,
so any available setpoint action can be made in response to external pulse.
Third, one of the pulse inputs can be configured to sense the external
synchronization pulse in the event that external time reference is used for the
demand interval measurements (see
Section 4.3.6
)
Each of these applications is programmed in the instrument independently, i.e., each
pulse input can be configured for either application at the same time.
4.9 Relay Output Operation
The
PM295
provides four relay outputs. For the relay ratings, see technical
specifications in
Chapter 6
. The present relay status can be monitored via the front
panel and communications, and used as a trigger for setpoint operation.
Each relay can be configured to be operated via a setpoint, or to output pulses.
Setpoint Activated Relay
Using a programmable setpoint, the user can activate (energize) or deactivate (de-
energize) any relay output to provide alarm and control operations on external
equipment. Setpoint programming allows the user to close the relay contacts for
programmable time interval, so the user can produce both level (status
) and pulse
output of an arbitrary duration upon predefined events.
