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Information about using speed sensors

  • The sensing distance Sn is:
    • approx. 4...8mm for optical sensors, up to 15mm for type 3.DS.WM03.NCT2
    • approx. 1...8mm for magnetic sensors
    • approx. 1...1,5mm for inductive sensors
  • The pre-setting of all MPM units is sensor type NPN.

For optical sensors, the following rules apply:

  • With an absorbing surface (e.g. steel with gunmetal finish, dark) use a “light” reflector mark.
  • With a reflecting surface (e.g. steel unpainted, galvanized, polished) use a „dark“ reflector mark
  • The suitable reflector must be determined by trial and error.
  • For example, white or matt black insulation tape of felt-tip pen could be used for the reflector mark
  • The reflector mark must be approx. 20mm long. Only then is sufficient “attenuation” and therefore reliable speed acquisition possible.

Problem guide: fluctuating or incorrect speed

  • Check the switching state.
  • Change the sensor position to rule out external light influences (e.g. ceiling lighting). (1 pulse per revolution)
  • Only one reference mark must be attached to the rotating part! (1 pulse per revolution).
  • Protect the lenses of the sensor from contamination.

For magnetic sensors, the following rules apply:

  • Drill a hole Ø 6,2mm, depth 2.3mm in the rotor (e.g. flange). Stick the magnet in the hole with the black surface pointing out toward the sensor.

For inductive sensor, the following rules apply:

  • A metallic attenuation mark is always required. This mark (e.g. protruding screw or drill-hole) must be clearly delimited from its surroundings.
  • Only one reference mark must be attached to the rotating part! (1 pulse per revolution).
  • Because the distance is very small with inductive sensors, it is important to ensure that the sensor is surely fixed. It must be ensured that the minimum distance of 1mm is always maintained. If the rotating and static parts touch, damage will inevitably result.

Function test with the BMT100M resp. 230M

  • When the sensor is attenuated (e.g. turn the spindle past the sensor by hand), a + and – sign must alternate once per revolution in the top left-hand corner of the display as the reference mark is detected, with the BMT230M a white square appears.

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