It is impossible to display an alarm on any HMI in existance "as soon as the alarm condition declaired by PLC".
An alarm condition in a PLC must remain in an alarm state for at least one complete polling cycle of the communications link between an HMI and a PLC.
Typical HMI's monitor a "Tag", which is connected to a data server, which is connected to a PLC. The Data Server only polls the PLC for information periodically. Even if you try to poll every millisecond, you won't be getting an accurate value for every point in the PLC every millisecond. Commonly, HMI alarming is polled on a 250, 500, or 1000 millisecond basis.
If you know that your data server is polling at 250msec or faster, than to assure that an HMI can 'see' an alarm condition, you must make sure the alarm condition is maintained for AT LEAST 250msec... and preferably, add 10% to that, so you want the alarm 'Bit' to stay 'Active' for at least 275msec.
(Caveat: If the HMI is PART of the PLC, as some smaller 'integrated HMI/PLC's are, it just might be possible)
Wsandeep said:
Hi
Please help me to understand how alarm tagging to be done so that alrm desplay on HMI as soon as alarm condition declaired by PLC