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User Manual
Piccolo Range
4.4 Alarms
Alarms are used to alert an operator when a pre-set level has been exceeded. They are
indicated by flashing the alarm number and the red ALM beacon in the display.
Up to three process alarms may be configured using the Quick Start Codes, section 4.1.1. or
‘P’ Codes P21 to P29.
They may also switch an output, usually a relay, to allow external devices to be operated when an alarm occurs (‘P’
code P11 to P14).
Each alarm can be configured to the types listed below:-
Alarm Type
Full Scale Low
Full Scale High
Deviation Low
Deviation High
Deviation Band
Description
The alarm is shown if the process value falls below an absolute threshold
The alarm is shown if the process value rises above an absolute threshold
The alarm is shown if the process value deviates below the setpoint by a set threshold
The alarm is shown if the process value deviates above the setpoint by a set threshold
The alarm is shown if the process value deviates above or below the setpoint by a set threshold
In addition to the above alarms the following alarm types may be configured:-
Sensor Break If the sensor becomes open circuit the alarm message Sb.r is flashed in the display. The controller
control outputs can be configured to output a ‘safe’ value. ( ‘P’ code P36).
Excess Current
Loop Break
An alarm will be indicated if the current is exceeded. (‘P’ code P33).
Current alarms can be Load, Leakage, Overcurrent
The loop is considered to be broken if the PV does not respond to a change in the output in a given
time. (‘P’ code P34).
If an alarm is not configured it is not shown in the list of level 2 parameters shown in section 4.7.2.
4.4.1 To Set Alarm Setpoints
The levels at which alarms operate are adjusted by the alarm setpoint parameters AL1, AL2 or AL3. By default,
these can only be set in Operator Level 2*, (section 4.7.2). If the controller is configured to measure load
conditions, parameters Ld.AL, LE.AL, Hc.AL are used to set alarm setpoints for load currents.
Press until the required alarm setpoint is shown *.
Press or to raise or lower the alarm setpoint.
Press to accept the value.
* The alarm setpoint parameters can be ‘promoted’ to Level 1 using iTools (section 10.5.3).
4.4.2 Alarm Indication
If an alarm occurs, the red ALM beacon will flash together with the alarm number, for example AL1. If more than
one alarm is present each alarm number is flashed in turn. Any output (usually a relay) attached to an alarm will
operate. An alarm relay can be configured, using the Quick Start Codes or the ‘P’ codes P11 to P14, to be
energised or de-energised in the alarm condition. It is normal to configure the relay to be de-energised in alarm so
that an alarm is indicated if power to the controller fails.
4.4.3 To Acknowledge an Alarm
There are three ways in which an alarm can be acknowledged:
1. In all cases an alarm can be acknowledged in Level 2, or in Level 1 if it is a latching alarm, as follows:-
Press to select Ac.AL (Alarm Acknowledge). This parameter is always present in operator level 2, unless a
function key has been configured for Alarm Acknowledge (‘P’ code P71, P72 or P73).
Press or to select YES.
Press
to accept.
2. By operating an external pushbutton attached to Digital Input 1 or 2, if either of these have been configured for
Alarm Acknowledge (‘P’ code P51 and P52).
3. Press or or if any of these buttons have been configured for Alarm Acknowledge (‘P’ codes P71,
P72 and P73).
If the alarm is still present the ALM beacon will light continuously and the alarm message will continue to flash.
The action which takes place depends on the latching type of the alarm configured, as described in the next
section.
☺
‘P’ codes are found
in section 5.2.
26 Part No HA031260 Issue 1 May -12