How to adjust the normally open and normally closed state of a fiber optic sensor

Fiber optic sensors can be configured to normally open (NO) or normally closed (NC) by using the sensor's output mode switch or programming function, which determines whether the output activates on light detection or absence.Understanding NO and NC ModesNormally Open (NO): The sensor output is OFF when no object is detected. It turns ON when the sensor detects light or the target object within its sensing range .Normally Closed (NC): The sensor output is ON when no object is detected. It turns OFF when the sensor detects light or the target object . For through-beam sensors, NO mode activates when the beam is received, while NC mode activates when the beam is interrupted. Reflex sensors behave similarly, with the output changing when the object passes in front of the sensor .Steps to Configure the SensorLocate the Output Mode Switch or Button: Many fiber optic sensors, such as the Wenglor OPT2041/OPT2040, have a switch or teach-in button to select NO or NC mode .Select the Desired Mode:For NO, set the switch or press the button to the position that activates the output on light detection.For NC, set the switch or press the button to the position that activates the output on absence of light .Verify the LED Indicator: Most sensors have an LED that blinks or lights up to indicate the current output mode. For example, a yellow LED may blink a certain number of times to show the selected mode .Test the Sensor: Place an object in the sensing range and observe the output. Ensure it behaves according to the selected NO or NC configuration.Additional ConsiderationsSome sensors allow switchable NO/NC outputs, providing flexibility without rewiring .Ensure the sensor's output type (PNP or NPN) matches your control system requirements, as this affects how the NO/NC signal is interpreted .For sensors with teach-in functions, you may also need to adjust the sensing range to ensure reliable detection in the selected mode . By following these steps, you can reliably configure a fiber optic sensor to operate in either normally open or normally closed mode, ensuring proper integration with your control system.