Watlow EZ-ZONE RM Limit Module Rev C - Manual (Page 8)

Watlow EZ-ZONE ® RML Module • 5 • Chapter 1 Overview
A Conceptual View of the RML
The flexibility of the RML’s software and hardware
allows for variation in configurations. Acquiring a
better understanding of its functionality and capa-
bilities while at the same time planning out how the
controller can be used will deliver maximum effec-
tiveness in your application.
It is useful to think of the controller in three
parts: inputs, procedures and outputs. Information
flows from an input to a procedure to an output when
the controller is properly configured. An RML con-
troller can carry out several procedures at the same
time, e.g., monitoring for several different alarm situ-
ations, monitoring and acting upon digital inputs and
driving output devices such as audible alarms, lights
and contactors. Each process needs to be thought out
carefully and the controller’s inputs, procedures and
outputs set up properly.
Inputs
The inputs provide the information that any given
programmed procedure can act upon. Simply stated,
this information may come from an operator pushing
a button or from a sensor monitoring the tempera-
ture of a part being heated or cooled.
Each analog input typically uses a thermocouple,
RTD or thermistor to read the process temperature.
It can also read volts, current or resistance, allowing
it to use various devices to read humidity, air pres-
sure, operator inputs and others values. The settings
in the Analog Input Menu (Setup Page) for each ana-
log input must be configured to match the device con-
nected to that input.
Each digital input reads whether a device is active
or inactive. An RML equipped with digital input/out-
put hardware includes two sets of terminals where
each of which can be used as either an input or an
output. Each pair of terminals must be configured
to function as either an input or output with the di-
rection parameter in the Digital Input/Output Menu
(Setup Page).
Functions
Functions use input signals to calculate a value. A
function may be as simple as reading a digital input
to set a state to true or false, or reading a tempera-
ture to set an alarm state to on or off. Alternatively,
if a failure with the primary sensing device should
occur the limit could trip a contactor removing power
from the heating element to avoid damaging the load.
To set up a function, it’s important to tell it what
source, or instance, to use. For example, if the control
is equipped with digital inputs they can be config-
ured to reset an individual alarm or all alarms. If
configured as such, the next step would be to define
which of the available digital inputs would be tied to
the alarm reset function. The RML module can be
equipped with up to 7 digital inputs, instance 1 - 6
and or 9. Once the specific input has been selected
simply assign the alarm reset function to it (Setup
Page, DIO Menu). The last step would be to define
the alarm instance that should be reset. If zero is en-
tered for the alarm instance when the digital input
selected above is enabled, all latched alarms without
a currently existing alarm condition will be reset. If
a specific alarm instance (1 -16) is selected it will be
that instance alone that will be reset.
Note:
Alarms will reset automatically when the condition
that caused the alarm goes back to a non-alarm
state if the alarm latching prompt is set to non-
latching (Setup Page, ALM Menu).
Keep in mind that a function is a user-programmed
internal process that does not execute any action out-
side of the controller. To have any effect outside of the
controller, an output must be configured to respond
to a function.
Outputs
Outputs can perform various functions or actions in
response to information provided by a function, such
as removal of the control voltage to a contactor; turn-
ing a light on or off; unlocking a door; or turning on
an audible alarm.
Assign an output to a function in the Output
Menu or Digital Input/Output Menu. Then select
which instance of that function will drive the select-
ed output. For example, in using a Limit Control an
output can be configured to respond to an alarm, i.g.,
(instance 15) or to a limit condition.
You can assign more than one output to respond
to a single instance of a function. For example, alarm
2 could be used to trigger a light connected to output
1 and a siren connected to digital output 5.
Input Events and Output Events
Input events are internal states that are set by the
digital inputs. Digital Input 1 provides the state of
input event 1, and Digital Input 2 provides the state
of input event 2. The setting of Digital Input Func-
tion (Setup Page, Digital Input/Output Menu) does
not change the relationship between the input and
the event. An input will still control the input event
state, even if Digital Input Function is set to None.
Actions
Based on a given input (Digital I/O, Event output,
Logic function, etc..) the Action function can cause
other functions to occur. To name a few, set alarms to
off, silencing alarms and reset a tripped limit condi-
tion. Energise
Module Limit
This function allows the user to setup a single out-
put to reflect an energized (safe) or deenergized
(tripped) state for the module. If any configured limit
is tripped (process value exceeds set point or limit in-