NARVA electrical components Germany NARVA model NARVA price

NARVA electrical components are linear devices based on metallic induction. The function of a sensor is to convert various measured physical quantities into electrical signals. In production processes, displacement measurement is generally divided into two types: measuring physical dimensions and measuring mechanical displacement. Depending on the form of transformation of the measured variable, displacement sensors can be classified into analog and digital types. Analog types can be further divided into physical-property type and structural type. Commonly used displacement sensors are mostly analog structural types, including potentiometric displacement sensors, inductive displacement sensors, synchros, capacitive displacement sensors, eddy-current displacement sensors, and Hall-effect displacement sensors. An important advantage of digital displacement sensors is that they facilitate direct input of signals into computer systems. Displacement is a quantity related to the movement of an object's position during motion, and the scope of displacement measurement methods is quite extensive. Small displacements are typically detected using strain-gauge, inductive, differential transformer, eddy-current, and Hall sensors, while large displacements are commonly measured using sensing technologies such as induction synchronizers, optical gratings, capacitive gratings, and magnetic gratings. Among these, optical grating sensors are increasingly widely used in industries such as machine tool machining and testing instruments due to their advantages, including ease of digitization, high precision (with current highest resolution reaching the nanometer level), strong anti-interference capability, absence of human reading errors, convenient installation, and reliable operation.

NARVA electrical component principle

Lasing principle of laser diodes: The P-N junction in a laser diode is formed by two doped gallium arsenide layers. It has a parallel-end structure, with one end mirrored (highly reflective surface) and the other partially reflective. The wavelength of the emitted light is directly related to the length of the cavity. When the P-N junction is forward-biased by an external voltage source, electrons move through the junction and recombine as in a conventional diode. When electrons recombine with holes, photons are released. These photons strike atoms, causing more photons to be released. As the forward bias current increases, more electrons enter the depletion region, resulting in the emission of more photons. Eventually, some photons drifting randomly within the depletion region strike the reflective surfaces perpendicularly and are reflected back along their original paths. The reflected photons are again reflected from the other end of the junction. This movement of photons from one end to the other occurs continuously multiple times. During photon movement, more atoms release more photons due to the avalanche effect. This process of reflection and generation of increasing numbers of photons produces a very intense laser beam. Each photon generated in the emission process described above is identical to other photons in energy level, phase relationship, and frequency. Therefore, the emission process yields a laser beam of a single wavelength. To generate a laser beam, the current of the laser diode must exceed a certain threshold level. Current below the threshold level forces the diode to behave as an LED, emitting incoherent light.

NARVA electrical component principle

In addition to the function of converting optical signals into electrical signals, like photodiodes, phototransistors also have the function of amplifying electrical signals. The appearance of a phototransistor is not much different from that of a general transistor. Generally, a phototransistor has only two terminals brought out—the emitter and the collector—while the base is not brought out. The casing also has a window to allow light to enter. To increase illumination, the base region area is made large, while the emitter region is small, so that incident light is mainly absorbed by the base region. During operation, the collector junction is reverse-biased, and the emitter junction is forward-biased. In the absence of light, the current flowing through the transistor is the dark current Iceo = (1 + β) Icbo (very small), which is even smaller than the penetration current of a general transistor; when illuminated, a large number of electron-hole pairs are excited, causing the base current Ib to increase. At this moment, the current flowing through the transistor is called the photocurrent, and the emitter current Ie = (7 + β) Ib. It can be seen that phototransistors have higher sensitivity than photodiodes.

NARVA electrical component characteristics

Under normal circumstances, the actual static characteristic output of a sensor is a curve rather than a straight line. In practical work, to enable instruments to have uniformly scaled readings, a fitted straight line is often used to approximately represent the actual characteristic curve. Linearity (non-linear error) is a performance indicator of this degree of approximation. There are various methods for selecting the fitted straight line. For example, the theoretical straight line connecting the zero-input and full-scale output points can be used as the fitted straight line; or the theoretical straight line that minimizes the sum of squared deviations from each point on the characteristic curve can be used as the fitted straight line, known as the least-squares fitted straight line.

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