Question: An industrial furnace is to he controlled as follows: The contacts of a bimetallic strip inside the furnace close if the temperature falls below the set point, and open when the tempera lure is above the set point. The contacts regulate a control relay that turns the heating elements of the furnace on and off. If the door to the furnace is opened, the heating elements art temporarily turned off until the door is closed.
(a) Specify the I/O variables for this sys-tem operation and define symbols for them (e.g., X1, X2, C1,111).
(b) Construct the ladder logic diagram for the system.
(c) Write the low-level language statements for the system using the PLC instruction set in Table.
