As shown in FIG grounds HMC1001 and an operational amplifier (AMP04) and light emitting diode (LED) constituting the proximity switch circuit. As used herein, the op amp as a c
omparator. The length of about 6mm ~ 12mm magnet closer HMC1001, when moved to a certain position, MR bridge output voltage reaches 30mV, the comparator flip, output goes low the LED light. If the magnet is removed, the comparator outputs a high level so that the LED goes out. Obviously, this circuit is equivalent to a proximity switch with indicator light can be used to detect displacement, speed and other non-electricity. Adjusting the value of the resistor R1 can set the threshold voltage of the switch.