Panasonic manually set fiber sensor FX-311 with 12-turn potentiometer has been incorporated for fine adjustments. It enables detection of very fine differences. Moreover, since the pointer of indicator has a red backlight, you can confirm the position at a glance, even in a dark area. The light-emitting elements of conventional fiber sensors are affected by temperature and long-term use, changing their emission over time and requiring sensitivity readjustment. FX-311 (red LED type) employs the new "four-chemical LED", first used in the FX-301 (red LED type). This emitter greatly reduces adverse influences on emission performance, resulting in stable operation that almost never needs adjustment. The FX-311 series has a convenient built-in "assist function" which indicates the optimum sensitivity position by flashing rapidly when optimum sensitivity is reached. This enables easy and reliable sensitivity adjustment, which is convenient for a narrow sensing range requiring fine tuning.