Watlow ez-zone pm - Retransmitting a Process Value or Set Point

Watlow EZ-ZONE
®
PMI Controller • 191 • Chapter 9 Features
The Watlow NO-ARC relay is a hybrid relay. It uses a mechanical relay for the current load
and a triac (solid-state switch) to carry the turn-on and turn-off currents. NO-ARC relays
extend the life of the relay more than two million cycles at the rated full-load current.
Although a NO-ARC relay has signicant life advantages, a few precautions must be followed
for acceptable usage:
Do not use:
• Hybrid relays for limit contactors. A limit or safety device must provide a positive mechani-
cal break on all hot legs simultaneously
• DC loads with hybrid relays. The triacs used for arc suppression will turn off only with ac
line voltage
• Hybrid switches to drive any inductive loads, such as relay coils, transformers or solenoids
• Cycle times less than five seconds on hybrid switches
• On loads that exceed 264V ac through relay
• On loads that exceed 15 amperes load
• On loads less than 100mA
• NO-ARC relays in series with other NO-ARC relays
Retransmitting a Process Value or Set Point
The retransmit feature allows a process output to provide an analog signal that represents
the set point or process value. The signal may serve as a remote set point for another con-
troller or as an input for a chart
recorder documenting system per-
formance over time.
In choosing the type of retransmit
signal the operator must take into
account the input impedance of
the device to be retransmitted to
and the required signal type, ei-
ther voltage or milliamps. Typically
applications might use the retrans-
mit option to record one of the
variables with a chart recorder or to generate a set point for other controls in a multi-zone
application.
Outputs 1 and 3 can be ordered as process outputs. Select retransmit rЛЏt as the Func-
tion fn (Setup Page, Output Menu). Set the output to volts volt or milliamps ЛЏa with
Type o.ty. Select the signal to retransmit with Retransmit Source r.sr. Set the range of the
process output with Scale Low s.Lo and Scale High S.hi. Scale the retransmit source to the
process output with Range Low r.Lo and Range High r.hi.
When the retransmit source is at the Range Low value, the retransmit output will be at its
Scale Low value. When the retransmit source is at the Range High value, the retransmit out-
put will be at its Scale High value.
Retransmit
Retransmit Source
Output Scale
Range High
Range Low
Scale High
Scale Low