An error handler chart is a chart or a group of charts that run in a control strategy. The error handler charts will monitor the error queue for errors caused by an I/O unit going offline. If an error is found, the control logic in the chart will tell the controller to try to communicate with the I/O unit again. If the I/O unit has come back online, the controller will re-establish communication to the I/O unit. If the I/O unit has not come back online yet, the controller will not be able to talk to the I/O unit and another error will appear in the error queue.
Error handler charts can be very important and we suggest that every strategy has one. We even offer a pre-made error handler chart that you can import into your strategy and then start from your power-up chart. This example error handler comes with the installation of PAC Project and can be found C:\Program Files\Opto22\PAC Project 8.0\Control Basic Examples\Error Handler Simple.