In this lesson we are going to show you how to modify a value in the PLC. You are working on a new plant and you have a line of logic that is looking for a particular field device to be true before the logic will solve true but that field device isn’t yet installed. Let’s say that you need a valve, valve A on a tank to open when this other valve, valve B closes. You want to test valve A but valve B hasn’t been wired up yet. You can use a watch table in your control system software in order to overwrite the closed status of valve B so that you can test your logic. Let’s open this lesson see how easy it is to overwrite some values.