Emerson Rosemount 702 - Latching warnings; 6.4 Discrete output circuits, measurement option code 42; 6.5 Discrete output switch functionality

Latching warnings
WARNING
When state latching is enabled, the discrete variable reported to the system
will represent the latched value which may not be the actual state value
measured by the Rosemount 702 Transmitter
WARNING
Ensure that the state latch time value is long enough for the value to be
reported throughout the entire system to guarantee the state transition is
not missed. After configuring discrete latching function, check for proper
operation at the system level to ensure the desired state transitions are
captured as desired.
6.4 Discrete output circuits, measurement option code 42
The Rosemount 702 Transmitter has two channels that can each be
configured for discrete input or output. Inputs must be dry contact switch
inputs and these were described in a preceding section of this document.
Outputs are a simple switch closure to activate an output circuit. The
Rosemount 702 Transmitter output does not provide any voltage or current,
the output circuit must have power of its own. The Rosemount 702
Transmitter output has maximum switch capacity per channel of 26 volts DC
and 100 milliamps.
Note
It is very important that the polarity of the output circuit is as shown in the
wiring diagrams, with the positive (+) side of the circuit wired to the +
terminal of each channel, and the negative (-) side of the circuit wired to the
CMN terminal. If the output circuit is wired backwards it will remain active
(switch closed) regardless of the state of the output channel.
6.5
Discrete output switch functionality
The discrete output of the Rosemount 702 Transmitter is driven by the host
control system, through the Wireless Gateway, and out to the transmitter.
The time required for this wireless communication from the Gateway to the
transmitter is dependent on many factors, including the size and topology of
the network and the total amount of downstream traffic on the wireless
network. For a network that is constructed to our best practices, typical
delays in communication of a discrete output from the Gateway to the
transmitter are 15 seconds or less. Remember that this delay is only part of
the latency that will be observed in a control loop.
April 2021 Quick Start Guide
Quick Start Guide 27