Event Trend, Easy Chart

Ignition
1

Hi All,

I’m trying to setup an easy chart to only display pen data when a particular event has occurred. My pens are

Pens:
-pH
-Temperature

Event (only display data when this event is true):
-Valve Open

There must be basic way to do this ?

2

The Tag History system stores samples individually, and without any reference to the conditions of other tags. The SQL Bridge’s transaction groups do, as it stores multiple values per row. With transaction groups, two simple solutions are possible:

  • Record pH and Temperature together at a suitable pace, with the Valve Open status as a trigger condition. Use “Database Pens” in the Easy Chart to display the values. The EasyChart simply won’t have data to display when the valve is closed, leaving a gap on the chart.
  • Record pH, Temperature, and Valve Open status together at a suitable pace. Then in the configuration of the EasyChart Pens, include a where clause that checks the Valve Open status. This will also omit the data from the chart, but it will remain available for other historical purposes.
3

Thanks Pturmel,

I thought where clause might have been the answer but it did not seem to work for me earlier today. I’ll check over things again in the morning. I used an expression binding for the where clause {valve open tag}=1, I assume that is ok?

4

No. A pen's where clause must be in SQL format, as the database actually executes it when the EasyChart retrieves the data. If you mean as a transaction group trigger condition, no, you must set up an execute-always item in the transaction group, and use it in the trigger settings for the group.