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Rotation detector operating principle

Electromagnetic Detector operating principle

MP-900/9000 series
MP-900/9000 series

Gear-mounted electromagnetic detectors are typically positioned close to the teeth of a detection gear attached to a rotating shaft, generating a signal with a frequency proportional to the rotational speed.
It consists of a permanent magnet, a detection coil, and a yoke. When a magnetic material approaches near the yoke, the magnetic flux passing through the detection coil changes, and an induced voltage with a frequency proportional to the change is generated in the detection coil.
The magnetic flux pulsates with a frequency f = rotational speed (r/min) × number of teeth / 60 (Hz), and this is output as the rotation signal of the detector.

  • Electromagnetic Detector Operating Principle No. 1
  • Electromagnetic Detector Operating Principle No. 2
  • Electromagnetic Detector Operating Principle No. 3

Features include,

  1. Simple structure

  2. No power required

  3. small size

  4. No maintenance required

These are some of the reasons why it is widely used in various fields as a reliable method for measuring rotation.

Operating principle Magneto-Electric Rotation Detector

Magneto-Electric Rotation Detector Operating Principle No. 1

Magneto-Electric Rotation Detector utilize magnetoresistive elements and are designed primarily for rotational measurement.
A magnetoresistive element is one whose resistance changes depending on the strength of the magnetic field. Typically, a constant magnetic field is applied using a magnet, and when a detection metal (gear) approaches the element, the magnetic field changes, and this change is detected as a change in resistance.
By using two elements, the influence of changes in the gap on the detected magnetic flux is reduced, and a stable detection signal can be output.

A bridge circuit is constructed using two magnetoresistive elements and two resistors, as shown in the diagram. The detection signal is extracted as a differential output and amplified by a DC amplifier.
To adjust for variations in the resistance values of the magnetoresistive elements, a potentiometer is used in the bridge circuit, and the bridge output is connected to a DC amplifier. Note that if an involute gear is used as the detection gear, the output waveform will be approximately a sine wave.
The output of the DC amplifier is passed to a waveform shaping circuit, where it is converted into a square wave with fast rise and fall times.
The magnetoresistive elements are arranged at the tip of the detector, and because gear detection is directional, the detector is marked with alignment marks.

  • Magneto-Electric Rotation Detector Operating Principle No. 2
  • Align the alignment marks with the direction of the gear teeth.
    Align the alignment marks with the direction of the gear teeth.

Photoelectric rotation detector: Operating principle

Photoelectric Rotation Detector: Operating Principle No. 1

The LG-9200 is a reflective photoelectric switch that uses an opto-fiber at the detector tip, making it particularly suitable for detecting minute objects and rotating bodies. Because the detector incorporates a light source (LED), photodetector (phototransistor), and amplifier, it has a compact and user-friendly design. The light source uses a pulse modulation method, making it highly resistant to ambient light, and it also has a built-in operation indicator light for easy monitoring of its operating status.

The oscillation circuit is a pulse modulation circuit that lights up the light-emitting diode (LED) light source, and it employs an astable multivibrator method.

The pulsed light emitted from the light source is reflected by the object to be detected. The output of the phototransistor is amplified to an appropriate level by an AC amplifier circuit, and then rectified and integrated by a detection circuit to convert it into a DC voltage. In the next stage, the waveform shaping circuit outputs HI when this DC voltage reaches a set level, and LO when it falls below that level.
The operation indicator light illuminates when the output level is HI, allowing you to confirm that the unit is working correctly.

  • Photoelectric Rotation Detector: Operating Principle No. 2
  • LG-9200 Measurable Range
    LG-9200 Measurable Range

最終更新日:2024/05/07