Limit and safety controllers respond to changes in what, and do what as a result?

Limit and safety controllers respond to changes in what, and do what as a result?

• A. They respond to changes in the controlled variable and make or break a circuit
• B. Change in color
• C. Change in energy price
• D. Change in location

Answer: (A)

Limit and safety controllers continually monitor the process variable—the measurement that indicates how the system is behaving. When that variable moves outside its safe range, they change the electrical circuit by opening or closing it, effectively stopping or limiting the energy supply to the appliance (such as shutting off a gas valve or burner). This is why they respond to changes in the controlled variable and then make or break a circuit.

Limit and safety controllers continually monitor the process variable—the measurement that indicates how the system is behaving. When that variable moves outside its safe range, they change the electrical circuit by opening or closing it, effectively stopping or limiting the energy supply to the appliance (such as shutting off a gas valve or burner). This is why they respond to changes in the controlled variable and then make or break a circuit.