M8002 is a Mitsubishi start-up pulse relay, which starts when the Mitsubishi PLC starts up and generates a pulse which can be used to initialize some parameters.
As soon as you start on a pulse, M8002 is taken to rise, along the three lines are: a power + 24 or other voltage, a ground line com 0V…, one is a signal line, you first turn on the 24V signal line and the ground line between, you see if there is any voltage.
Photoelectric switch as long as your wire pair, in the output line with a multimeter to detect voltage, often open is to detect the object when there is output, often closed is to detect the object when there is no output.
PLC as long as there is no trouble in itself, the M0 will be set up when the power is switched on. But it will happen only when the power is cut off or the stop button is activated again. Because M8002 is the boot pulse.
PLC ONE 