Planar inductive sensor for small displacement

Abstract

This paper presents a meander type displacement inductive sensor, developed in printed circuit board (PCB) technology. It also describes design, realization and the input inductance measurement of sensor. The displacement in two directions (less than 0.5 mm) can be detected by using two sensor's elements (i.e. two pairs of meander coils). In each pair, one of the coils is fixed, and between its terminals the input inductance was measured, while other coil is short-circuited. If one coil is moved above the other in directions of x-and z-axes, coupling between coils will change, as well as input inductance, which serves as a measure of displacement. In order to achieve better linearity of the sensor, gap is inserted in the middle of each conductive segment of fixed coils. Four sets of inductive sensors were realized: without gap and with three different gaps: 0.25 mm, 0.51 mm and 0.76 mm. In addition, a simple model of the inductive sensor is proposed. Using this model, the input inductance of displacement sensor was calculated and compared with measured values. A good agreement was found.

A new method of planar inductive sensor for industrial application

“…[12] Looking at the equation for resonant Clapp, it can be seen that the influence of the capacitances C1 and C2, and the capacitance of the transistor, no longer exist. Only the capacitor C3 and the element L are variables that comprise equation.…”

“…Thus, it is feasible to build a tank circuit for the best operating characteristics, and thereby obtain better frequency response and stability of the oscillation frequency. [12] As the technology of the comparator circuit and output can then be presented for both the conventional line as the conventional line with increased distance, and the variable cost factor in this case. [12].…”

“…[12] As the technology of the comparator circuit and output can then be presented for both the conventional line as the conventional line with increased distance, and the variable cost factor in this case. [12].…”

“…[11] [12] However, even if there is little widespread technology in the area of industrial automation and inductive sensing for analysis, it is possible to build topologies of LC oscillators [1] well-founded and conduct a study of oscillator topologies which would be more convenient to construct an inductive sensor with front sensor using planar technology.…”

“…[11] [12] A circuit is defined as a planar circuit with two relevant dimensions (X and Y axis) while the third dimension (Z axis) is typically a fraction of the wavelength according to the frequency used. [11] We can see such characteristics according to Figure 7.…”