Topic: DMD0003

ALRATE - Rate of Change Alarm

The Rate of Change Alarm instruction (ALRATE) monitors the Input at the specified Sample Time and sets one or both of the designated alarm bit locations if the Input has changed more than the Rate Limit.

Parameters:

Note: Use the F9 key (Element Browser) or Down-Arrow key (Auto-Complete) at any time to see a complete list of the memory locations that are valid in the current field of the instruction.

Input - identifies the memory location to monitor. This can be any readable numeric location.

Sample Time - specifies the frequency (in milliseconds) at which the comparison between the Input value and the Rate Limit is done. The Sample Time can be any positive integer constant value or any readable numeric location.

Rate Limit - specifies the maximum allowable change of the Input value from one sample time to the next. The Rate Limit can be any constant value or any readable numeric location.

Positive Alarm - (if selected) designates the bit location to turn ON if the Input value has increased by more than the Rate Limit since the last Sample Time, otherwise the bit will be turned OFF. This can be any writable bit location.

Negative Alarm - (if selected) designates the bit location to turn ON if the Input value has decreased by more than the Rate Limit since the last Sample Time, otherwise the bit will be turned OFF. This can be any writable bit location.

See Also:

• ALDEV - Deviation Alarm

• ALHILO - High/Low Alarm

• ALRATE - Rate of Change Alarm
   

• PID - Closed Loop Controller

Related Topics:

• Getting Started with PID Loops

• Using the PID View

• Using the PID Overview

• Using the PID Process Simulator in the Do-more Simulator

Rung Example: