Created Date: March 02,2016

Created by: sbenes

Of the alarms that remain, none of them will clear after pressing the Clear All button a second or third time. None of them require confirmation to clear either. Your third question deserves some thought however and after looking closely at the alarms that did remain and after testing this theory, I came up with the following conclusion.

I monitor the states of many inputs with the event manager database. It does work well to capture various states and conditions. However, after looking at kewakl's last question I realized that what's probably happening is that the alarms that are left in the list are ones whose state is currently true.

For example: an input gets turned on and it gets recorded as a line in the Alarm History of the touchscreen. The input turns off and that also gets recorded in the Alarm History. After pressing the Clear All button, only the alarm that happened when the input turned on, is removed from the list. Since the input is still in the "off " state, the alarm is still true and it remains in the list. I understand how this could be the case.

The problem with this is, a lot of these alarms will never clear because their states may never change. I may stop monitoring the input or I may load completely different ladder logic, or power cycle the PLC. The same alarms will always remain in the list. The Clear All button should do just that, clear ALL alarms and start monitoring again from that point on. Otherwise, it's not as useful a tool as it should be.

It seems the choices I have now are to, 1)just deal with seeing all the old alarms in the alarm history that won't clear, or 2)modify my event manager database to be extremely selective when choosing the inputs I monitor.

Thanks for posing the question kewakl.

Created Date: March 02,2016

Created by: kewakl

You are welcome.

I don't know what PLC you are using, but can you migrate your (OFF=ALARM) for HMI alarm history bits in PLC to another bit that is TRUE when the (original) alarm bit GOES false and use the inverted states - just for the alarm history, but leave the PLC alarm handling as-is.

FirstScanBit OriginalAlarmBit InvertedBit

OFF = ALARM ON = ALARM

ExistingAlarm CanBeCLEARED

---------]/ V

FirstScan to inhibit the Inverted bit from setting at Power-On or into Runmode

It may need more massaging.....

Created Date: March 02,2016

Created by: kewakl

I may stop monitoring the input or I may load completely different ladder logic, or power cycle the PLC. The same alarms will always remain in the list. The Clear All button should do just that, clear ALL alarms and start monitoring again from that point on. Otherwise, it's not as useful a tool as it should be.

Maybe you need a REALLY! CLEAR ALARM HISTORY! REALLY! ! ! button.

Seriously, you would probably need to remove the alarm from the event manager if you decide to stop monitoring a specific bit that alarms in the OFF state.

If the event/alarm exists in the event manager, it follows that it should alarm whenever the specified trigger state is matched. In the HMI, that is ON or OFF for bits.

Created Date: March 01,2016

Created by: sbenes

I have a huge number of EA7 6 " touchscreens installed in the field and I 've never been able to completely clear any of the Alarm History screens on any of them. Is there some trick to this? It will clear out some of them by using the clear all button, but it always leaves a large number of them untouched. These alarms are from the event manager that I have set up for various PLC states and conditions.