FDC DIN Controls - Alarm Logic

Alarm Logic: Process, Deviation, Deviation Band, Dwell Timer, Heater Break & Loop Break

 

Process Alarms [applicable to B, C, 90, 100, 300 & P Series Controls - not 200 Series Controls]

A Process alarm has a specific SP set within the configured operating span of the instrument. When the process exceeds this SP an alarm occurs. The process alarm SP is independent from primary control setpoint [output #1].

 

Deviation Alarms: [applicable to B, C, 90, 100, 200, 300 & P Series Controls]

A Deviation alarm has a positive or negative SP relative to the primary control [output #1] SP.

Example: SP = 100F with deviation alarm set at +20F. When process exceeds 120F an alarm is triggered.

 

Deviation Band Alarm: [applicable to B, C, 90, 100, 200, 300 & P Series Controls]

A Deviation Band alarm presents two reference levels to SP [output #1].

Example: SP = 100F with deviation band alarm of 20F. When process is within 20F of SP no alarm.

 

Latching or non-Latching Alarm Configuration: [applicable to 200, 300, B42 & P Series]

Non-Latching: Alarms clear when PV is no longer within alarm setting

Latching: Alarms do not clear until PV is no longer within alarm setting AND operator depresses the scroll key

[Note: The L Series FM approved High Limits output #1 is always latching. The L Series optional 2nd relay output is configurable as either latching or non-latching.]

 

Alarm Configuration - High or Low: [applicable to B, C, 90, 100, 200, 300 & P Series Controls]

High: Alarm relay closes when PV exceeds alarm SP

Low: Alarm relay closes when PV is lower than alarm SP

 

Alarm Hold Function: [applicable to B, 90, 100, 200, 300 & P Series Controls - not C Series Controls]

A Holding alarm prevents alarm conditions on power up.

The alarm is enabled only when the process reaches SP [output #1].

After PV reaches SP the alarm functions as a normal alarm.

 

Alarm Action in Control Failure Mode: [applicable to B, C, 90, 100, 200, 300 & P Series Controls]

Alarms are configurable to close or open on control failure.

 

Dwell Timer Alarm: [B, C, 90, 100, 200, 300 & P Series Controls]

One alarm may be configured as a dwell timer alarm. Once configured the dwell time is measured in minutes - the maximum number of minutes vary by control series with the longest being the 300 Series at 6,553 minutes. Once the process reaches setpoint the dwell timers starts to count down from zero until time out. The dwell timer alarm relay will remain unchanged until time out. The dwell timer is reset by power up sequence.

[Note: The 300 Series event input may be configured to reset the dwell timer]

 

Alarm Modes Unique to the 300 Series Controls

Heater Break Alarm: [applicable to 300 Series Controls]

A Current Transformer [CT; 0-50A] is connected to Input #2.

An alarm is configured as a process alarm. Alarm occurs when current draw exceeds alarm SP.

 

Loop Break Alarm: [300 Series Controls only]

Loop Break Conditions are detected during a time interval of 2 x TI1 [double the integral time but 120 seconds maximum]. Hence there is a delay for the alarm to respond to actual Loop Break. If the process variable doesn't increase (or decrease) while the control output has reached its' maximum (or minimum) value within the detecting time interval a Loop Break Alarm occurs [when an alarm is configured as Loop Break Alarm].

 

Sensor Break: [applicable to 300 Series only]

Alarm may be configured as a sensor break alarm and is activated as soon as failure mode occurs. Note that A-D failure also creates a sensor break alarm.

 

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Return to:

Process & Temperature Control Page.htm

90 Series.htm

300 Series.htm

100/C Series.htm

B Series.htm (board level control)

Limit Controls.htm

P Series Profile Controls.htm

 

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