Instrumentation

The Barkhausen effect relates magnetism to acoustics. In 1919, a German scientist Heinrich Barkhausen found that whenever he moved a magnet close to an iron-cored wire, an audible roaring sound (called Barkhausen noise or Barkhausen emission) was heard through an amplified speaker. The sound reflects a sudden (instead of a smooth or gradual) shifting or […]

Magnetostrictive Sensor Working Principle The magnetostrictive effect relates a material’s elastic state to its magnetic state. Nearly all FM materials such as iron, nickel, cobalt, and their alloy, exhibit a change in size and shape resulting from magnetization change. This effect is known as Joule effect. Joule effect can be understood by considering an FM

When a current flows through a thin flat conductor placed in a magnetic field, the magnetic field exerts a transverse force (i.e., Lorentz force) on the moving charge carriers and pushes them to one side of the conductor. The charge then builds up and forms a measurable voltage between the two sides of the conductor.

Fluxgate sensors are precise vector sensors of magnetic fields (can measure both magnitude and direction). A fluxgate sensor uses a soft magnetic material (with a low coercive force/field and high permeability) as its core material and operates under magnetic saturation state. In saturation, the permeability of the core drops, causing the flux associated with the

Synchro has a single winding rotor that rotates inside a stator of three windings, much like an electric motor as shown in Figure 1. The primary winding wound around the rotor is excited by an alternating current, which induces currents to flow in three Y-connected secondary windings (oriented 120° apart). The relative magnitudes of secondary

LVDT is an inductive device. It has a primary coil, two secondary coils, and a linearly movable core. The primary coil is driven by an AC excitation current, which creates a varying magnetic field. This changing field induces an AC voltage or current in the secondary coil (usually two or three windings) that can be

Characteristics of Strain Gauges The core element of a piezoresistive sensor is the strain gauge. The characteristics of a strain gauge are mainly defined by the gauge dimensions, resistance, gauge factor, temperature coefficient, resistivity, and thermal stability. Gauge dimensions and shape are very important in choosing a right type of strain gauge for a given

When electromagnetic radiation, such as, infrared light, visible light, or ultraviolet (UV) light, strikes a photoconductive material, the resistance of the material decreases. This occurs because the electrons in the valence band of the photoconductive material are excited by the light and move to the conduction band, which increases the material’s conductivity. The amount of

An RCIM sensor is a sensor that results in a change in electrical resistance, capacitance, inductance, electrical field, or magnetic field when it is exposed to a physical, chemical, or biological stimulus. Its output could be a voltage, current, electrical charge, time, or frequency to reflect these changes. Following are the most important characteristics of

Encoders are non-contact, optical-based digital devices that are used for measuring displacement. They can be used to measure both linear and rotary displacement. We will concentrate on rotary-type encoders, which are widely used in motion-control applications. Rotary encoders are available as incremental or absolute type. An incremental encoder measures changes in rotation from some datum