I bought X2 of these for lathe tachometers .
I am using a neo magnet on the spindle . The readout is unstable, it wanders about +5 and -5 rpm . I have tried running it from a regulated supply and varying the supply voltage - no effect . I also shortened the sensor head lead as it may be picking up stray interference , no effect . Also tried different magnets and positions, no effect . The LED in the sensor head is flickering as it should as the magnet passes the sensor - it has NPN written on the head, a transistor is in there ?
Any ideas . It may be that these are cheap junk from China and the unit is actually running within specs .
I am using a neo magnet on the spindle . The readout is unstable, it wanders about +5 and -5 rpm . I have tried running it from a regulated supply and varying the supply voltage - no effect . I also shortened the sensor head lead as it may be picking up stray interference , no effect . Also tried different magnets and positions, no effect . The LED in the sensor head is flickering as it should as the magnet passes the sensor - it has NPN written on the head, a transistor is in there ?
Any ideas . It may be that these are cheap junk from China and the unit is actually running within specs .
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