There may come a time in your career when you are called to investigate a malfunction in an existing control system that someone else has written. The field device documentation may be scarce or even nonexistent and you don’t know what field device belongs to which address. You could press each switch to determine what address is associated with it but you need a central location, with all of the addresses, to see them all at once when the switch is pressed, particularly with a large program. One of the best options is a watch table. A watch table is a table that you populate with the addresses that you want to monitor. There is a monitor value column that tells you the current value of the addresses. Let’s get started with this lesson and monitor some addresses.