How the Wiegand Effect is used in Sensing Instruments

The Concept behind Wiegand Effect Based Sensors  

The Wiegand effect technology employs the unique magnetic properties of specially processed, small-diameter ferromagnetic wire. By causing the magnetic field of this wire to abruptly reverse, a sharp, uniform voltage is generated. This pulse is referred to as a Wiegand pulse. Sensors employing this effect need only a few simple components to produce sharply defined voltage pulses in response to changes in the applied magnetic field. These sensors typically consist of a short length of Wiegand wire, sensing coil, and alternating magnetic fields that generally are derived from small permanent magnets.

In reference to the above figure, when an alternating magnetic field of appropriate strength is applied to the Wiegand wire, the magnetic field of the cores switches polarity and then reverses, causing the Wiegand pulse to be generated. These alternating magnetic fields are usually produced by magnets that are attached to the rotating or moving apparatus, by a stationary read head and moving Wiegand wires, or by an alternating current generated field.

The Sensing Applications employing Wiegand Effect Technology

The Wiegand effect technology is effective for proximity sensing, tachometry, rotary shaft encoding and speed sensing in applications such as:

• Measuring shaft speed in engines and other machinery.
• Tachometers, speedometers and other rotational counting devices.
• Electronic indexing for water, gas, and electric meters as well as remote metering systems.

Advantages of Wiegand Effect Based Sensors

The key advantages of the Wiegand effect based sensors include:

• There is no requirement for external power.
• The sensors are noncontact with no wear.
• Two-wire operation.
• 20 kHz pulse rate.
• High-level voltage output pulse.
• They have a wide operating temperature range for instance, -40 °C to +125 °C.

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