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Rotation Detector Operating Principle

Electromagnetic Detector Operating Principle

MP-900/9000 Series
MP-900/9000 Series

The external gear type electromagnetic detector generates a signal with a frequency proportional to the rotational speed by bringing it close to the tooth tip of the detection gear mounted on the normal rotation axis.
It consists of a permanent magnet, a detection coil, and a yoke. When a magnetic material approaches the vicinity of the yoke, the magnetic flux passing through the detection coil changes, resulting in an induced voltage in the detection coil that is proportional to the change.
Since the magnetic flux pulsates at a frequency f = rotational speed (r/min) × number of teeth / 60 (Hz), this will be output as the rotational signal of the detector.

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

As a feature,

  1. simple structure

  2. No power supply needed

  3. small-sized

  4. No maintenance required

It is a highly reliable rotational measurement device that is widely used in various fields.

Magneto-Electric Rotation Detector Operating Principle

Magneto-Electric Rotation Detector Operating Principle No.1

The Magneto-Electric Rotation Detector is designed to apply magnetic resistance elements, primarily suitable for rotation measurement.
The magnetic resistance element changes its resistance value according to the strength of the magnetic field, and typically, a constant magnetic field is provided by a magnet. When the detecting metal (gear) approaches the element, the magnetic field changes, and this change is detected as a change in resistance value.
By using two elements, it is possible to reduce the influence on the detection magnetic flux due to changes in the gap, allowing for a stable detection signal output.

Two magnetoresistive elements and two resistors form a bridge circuit as shown in the diagram, extracting the detection signal as a differential output, which is amplified by a DC amplifier.
To adjust the variation in the resistance values of the magnetoresistive elements, a potentiometer is used in the bridge circuit, connecting the bridge output to the DC amplifier. When using an involute gear as the detection gear, the output waveform is almost a sine wave.
The output of the DC amplifier is passed to a waveform shaping circuit, resulting in a fast-rising and fast-falling rectangular wave.
The magnetoresistive elements are arranged at the tip of the detector, and since there is directionality in gear detection, alignment marks are indicated on the detector.

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

Optical rotary encoder operating principle

Photoelectric Rotary Detector Operating Principle No.1

The LG-9200 is a reflective photoelectric switch that uses optical fiber at the detector tip, making it particularly suitable for detecting small objects and rotating bodies. It features a compact and user-friendly design, as it incorporates a light source (LED), a light receiving element (phototransistor), and an amplifier within the detector. The light source operates on a pulse modulation method, which is resistant to interference from ambient light, and it also includes an operational indicator lamp, allowing users to confirm the operational status.

The oscillation circuit is a pulse modulation circuit that lights up the light-emitting diode, and it operates using an unstable multivibrator method.

The pulse light emitted from the light source is reflected by the detection target, and the output of the phototransistor is amplified to an appropriate level by the AC amplification circuit, then rectified and integrated by the detection circuit, converting it into a DC voltage. In the subsequent waveform shaping circuit, when this DC voltage reaches the set level, the output becomes HI, and when it falls below the level, it becomes LO.
The operation indicator lamp lights up when the output level is HI, allowing for operation confirmation.

  • Photoelectric Rotary Detector Operating Principle No. 2
  • LG-9200 measurable range
    LG-9200 measurable range

最終更新日:2024/05/07