L91 FM Approved Limit Controls - Special Features
Alarm Logic and Configuration:
Thermocouple & RTD Input Types
The L91 & L41 accept the following thermocouple & RTD inputs:
Display Configurations for Normal non-Alarm Condition
The L91 display may be configured as shown below for noraml non-alarm conditions.
LED Annuciators: The Output status annuciator LEDs, OP1 and OP2 show the status of the output relay(s), the display values being degrees C or F may be viewed at any time showing status of the output relay(s).
At any time the operator may view PV, High SP1, Low SP1, SP2 by depressing the scroll key and observing the annuciator below the display. The appropriate SP values will only be displayed if the control is so configured.
Display Logic while in Alarm Condition
When the process goes into either High or Low Alarm condition [output #1] the display will show Process Value [PV] and Output #1 annuciator LED will be energized.
At any time the operator may view PV, High SP1, Low SP1, SP2 by depressing the scroll key and observing the annuciator below the display interpret the display value. The appropriate SP values will only be displayed if the control is so configured.
The High or Low Alarm relay will stay latched until the PV is no longer in alarm condition and the operator depresses the Reset key.
How to Change Setpoint Value - Lock & Unlock Mode
High Setpoint 1, Low Setpoint 1 and SP2 values may be viewed at any time by depressing the scroll key and watch the annuciator below the display to interpret the display value. The Setpoint value(s) are not adjustable when the LOCK annuicator is energized.
Changing Setpoint(s) require the control to be in the UNLOCK mode.
The control is in the UNLOCK mode for three minutes after power-up and can be entered at any time by depressing the RESET key for a minimum of 4 seconds.
Using the Event Input as a Remote Reset disables the keypad UNLOCK function. The Remote Reset must be held in place for 4 seconds to allow SP changes.
Output #1 is available as a mechanical relay, 1A triac or ssr driver output.
Output #2 offers mutually exclusive options: mechanical relay, 1A triac, ssr driver, transmitter power supply, analog retransmission of SP or PV, RS485 Modbus communication or event input for remote reset. Discussion below assumes Output #2 is uses as an alarm relay, 1A triac or ssr driver output.
Configuration of both Output #1 and Output #2 alarm outputs: hysteresis value per Output, action with control failure, and upper & lower Setpoint limits within the operating range of the selected input.
Output #1: Latching Output available as a mechanical Form C [spdt] relay, 1A triac or ssr driver that may be configured as follows:
When the Process Variable is in an alarm condition Output #1 will latch its' output. The output can be cleared only when the Process Variable is no longer in alarm and the operator depresses the RESET key.
Output #2: Form A [spst] relay, 1A triac or ssr driver that may be configured as follows:
The non-latching configuration function as a normal process alarm - relay changes when in alarm condition and returns to original state when the PV in no longer in alarm.
The latching configuration function the same as output#1, relay is latched until the Process Variable is no longer in alarm condition and the operator depresses the RESET key.
The Limit Annuciator [Alarm Silence] configuration:
Event Input - Remote Reset of Latched Alarm or Lock Unit
Output #2 offers mutually exclusive options: a selection of a digital output [relay, triac, ssr driver], analog retransmission, RS485 Modbus and an Event Input. Shown below are configurations for the Event Input.
Event Input Configured for Remote Reset: Providing a dry contact closure to the Event Input terminals will perform the same function as depressing the RESET key.
Event Input Configured for Lock Unit: Providing a dry contact closure to the Event Input terminals will Lock the unit and not allow any parameter changes including Setpoint(s).
View Minimum, Maximum PV Values and Time in Alarm
The Maximum & Minimum PV values as well as the time output #1 is in alarm can be viewed in the Setup Mode.
The LOCK and UNLOCK sequence limit when Setpoint(s) may be changed and when entering UNLOCK the Maximum & Minimum PV values and time in alarm are reset. If interested in viewing these values first enter the Setup Mode and scroll down until these values can be read. Care should be taken not to depress the RESET key for 6 seconds even when in the Setup Mode so as not to enter the UNLOCK mode and inadvertanly clear the values.
After entering the UNLOCK mode the PV High & Low values will start from the current PV value and Time in Alarm will be reset to zero.
Communications - RS485 Modbus or Retransmission
Output #2 offers mutually exclusive options: a selection of a digital output [relay, triac, ssr driver], Analog Retransmission, RS485 Modbus and an Event Input. Shown below are configurations for the RS485 Modbus and Analog Retransmission. Click here for more information on Modbus & Analog Retransmission.htm.
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