Topic: DMD0003
ALRATE - Rate of Change Alarm
The Rate of Change Alarm instruction (ALRATE) monitors how quickly the value in a numeric memory location is changing, and sets alarm bits if the value has changed more quickly than a specified amount.
Parameters:
Note: Use the F9 key or click the 'three dot box' at the right edge of the parameter field to open the Default Element Selection Tool (the Element Picker or the Element Browser) or use the Down-Arrow key (Auto-Complete) on any parameter field to see a complete list of the memory locations that are valid for that parameter of the instruction.
Input is the numeric memory location to monitor. This can be any readable numeric memory location.
Sample Time is 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 memory location.
Rate Limit is 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 memory location.
Positive Alarm (if selected) selects 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) selects 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:
ALRATE - Rate of Change Alarm
Related Topics:
Getting Started with PID Loops
Using the PID Process Simulator in the Do-more Simulator
Rung Example:
