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A position sensor is a sensor that detects an object's position. A position sensor may indicate the absolute position of the object (its location) or its relative position (displacement) in terms of linear travel, rotational angle or three-dimensional space. Different from the displacement sensor, the position sensor has two types: contact type and proximity type. The contacts of the contact sensor are moved by the contact and extrusion of two objects, and the common ones are the travel switch and the two-dimensional matrix position sensor. The travel switch has simple structure, reliable action and low price. When an object is in motion and encounters the travel switch, its internal contacts will act to complete the control. For example, if travel switches are installed at both ends of the X, Y, and Z axes of the machining center, the movement range can be controlled. The two-dimensional matrix position sensor is installed on the inside of the robotic palm to detect the contact position between itself and an object. Proximity switch refers to a switch that can send an "action" signal when an object is close to a set distance, and it does not need to be in direct contact with the object. There are many types of proximity switches, mainly electromagnetic type, photoelectric type, differential transformer type, eddy current type, capacitive type, reed switch, Hall type, etc. The applications of proximity switches on CNC machine tools are mainly tool rest tool selection control, table travel control, oil cylinder and cylinder piston travel control, etc. Also, there are potentiometer position sensor, Lvdt position sensor and so on.

Potentiometer, a common electromechanical component, is widely used in various electrical and electronic equipment. A potentiometer sensor is a sensor that converts mechanical displacement through a potentiometer into a resistance or voltage output that is a function of it. According to their different structural forms, they can be divided into wire-wound type, thin-film type and photoelectric type. According to the characteristics of input and output, it can be divided into linear potentiometer sensor and nonlinear potentiometer sensor. Most commonly used single-turn wire-wound potentiometers. Potentiometer-type resistance sensors are generally composed of resistance elements, skeletons and brushes. The movement of the brushes relative to the resistive element can be linear, rotational or helical. When the measured changes, the brush contacts move on the resistive element, and the resistance value between the contact and the resistive element will change, and the linear conversion between the displacement and the resistance can be realized. The resistive sensor is a kind of electrical parameter sensor that has been used earlier. It has a wide variety of applications and is widely used. After measuring the circuit, the changes being measured are reflected. The potentiometric sensor has a simple structure, good linearity and stability, and can form a force measurement, pressure measurement, weighing, displacement measurement, acceleration measurement, torque measurement, temperature measurement and other detection systems with the corresponding measurement circuit. It has become one of the indispensable means of production process detection and realization of production automation.

A linear scale, also called a bar scale, scale bar, graphic scale, or graphical scale, is a means of visually showing the scale of a map, nautical chart, engineering drawing, or architectural drawing. A scale bar is common element of map layouts. On large scale maps and charts, those covering a small area, and engineering and architectural drawings, the linear scale can be very simple, a line marked at intervals to show the distance on the earth or object which the distance on the scale represents. A person using the map can use a pair of dividers (or, less precisely, two fingers) to measure a distance by comparing it to the linear scale. The length of the line on the linear scale is equal to the distance represented on the earth multiplied by the map or chart's scale. In most projections, scale varies with latitude, so on small scale maps, covering large areas and a wide range of latitudes, the linear scale must show the scale for the range of latitudes covered by the map. While linear scales are used on architectural and engineering drawings, particularly those that are drawn after the subject has been built, many such drawings do not have a linear scale and are marked "Do Not Scale Drawing" in recognition of the fact that paper size changes with environmental changes and only dimensions that are specifically shown on the drawing can be used reliably in precise manufacturing.