German PREH sensors PREH models PREH prices

PREH sensors are measurement feedback devices that operate based on the optical principle of gratings. Grating scales are frequently used in the closed-loop servo systems of CNC machine tools for detecting linear or angular displacement. The measurement output signal is a digital pulse, characterized by a large detection range, high detection accuracy, and fast response speed. For example, in CNC machine tools, they are commonly used to detect the coordinates of tools and workpieces to observe and track tool path errors, thereby compensating for tool motion errors. Depending on the manufacturing method and optical principle, grating scales are divided into transmission gratings and reflection gratings.

PREH sensor working principle

A magnetic induction sensor is a contact sensor; its structural schematic is shown in the figure. It consists of two alloy reeds with high magnetic permeability and low coercivity, sealed in a glass tube filled with inert gas. A certain overlap and appropriate gap are maintained between the two reeds, with gold-plated ends serving as contacts, and lead wires welded outside the tube. When the magnetic induction intensity at the sensor's location is sufficiently high, the two reeds attract each other, causing the contacts to close; when the magnetic field weakens to a certain extent, the reeds release under their own elastic force. When driven by a permanent magnet, magnetic induction sensors are mostly used for detection, such as limit switches, replacing travel switches that rely on collision contact, which improves system reliability and service life. They are often used in PLC controllers as communication signals for position control.

PREH sensor precautions

The voltage used for DC magnetic induction sensors is generally 3~30V DC, with a typical application voltage range of 5~24V DC. Excessively high voltage causes internal component temperature rise, making the sensor unstable, while excessively low voltage makes it susceptible to external temperature changes affecting magnetic field strength characteristics, leading to circuit malfunction. When using Hall sensors to drive inductive loads, please connect a freewheeling diode in parallel across the load terminals; otherwise, transient high-voltage pulses during long-term operation of the inductive load will affect the service life of the Hall sensor. To ensure safety, please check whether the wiring is correct and verify that the voltage is the rated value before powering on.

PREH sensor applications

1) Motor industry: Brushless motors offer a series of advantages, including compact size, light weight, high efficiency, convenient speed regulation, low maintenance, long service life, and no electromagnetic interference. The annual demand numbers in the hundreds of millions. In brushless motors, magnetic sensors are used for rotor magnetic pole position sensing and stator armature current commutation. Many magnetic sensors, such as Hall devices, Wiegand devices, and magnetoresistive devices, can be used, but Hall devices are the most widely used. Rotary encoders are used for motor speed detection and control; optical encoders were commonly used in the past. Magnetic encoders are showing increasing advantages and are gradually replacing optical devices. Magnetic sensors can also be used for motor overload protection (mainly using Hall current sensors) and torque detection. 2) Power electronics technology: Power electronics technology is the combination of power technology and electronic technology, enabling mutual conversion between AC and DC currents, and allowing free regulation of current, voltage, and frequency within required ranges. Using these technologies and products, various special power supplies (such as UPS, high-frequency power supplies, switching power supplies, arc welder inverter power supplies, etc.) and AC variable frequency drives (AC VFDs are used for motor speed control and offer excellent energy-saving effects) can be manufactured. The core of these conversion devices is high-power semiconductor devices. Various current sensors based on magnetic sensors are used to monitor, control, and protect these high-power devices. Hall current sensors have fast response speeds and rely on magnetic field coupling with the controlled circuit without connecting to the main circuit, resulting in low power consumption, strong overload resistance, good linearity, and high reliability. They can serve as overcurrent protection drivers for high-power devices and as feedback devices, becoming a control link in automatic control loops. Using conversion technology can save significant amounts of energy; abroad, 95% of electrical energy is obtained through conversion. Although conversion technology has received high attention domestically, only 5% of electrical energy undergoes this conversion, indicating huge application prospects. This area, which may absorb a large number of current sensors, is another huge industrial application field for magnetic sensors. 3) Energy management: The automatic detection system of the power grid needs to collect large amounts of data. After computer processing, it monitors the operating status of the power grid and performs load distribution adjustment and safety protection. Each control link of the automatic monitoring system can be implemented using current sensors and transformers based on magnetic sensors. Hall current sensors are gradually being applied in power grid systems. Electricity meters made with Hall devices are shifting from development to practical application; they can automatically bill and display the power factor for timely adjustment, ensuring efficient electricity usage. 4) Mechanical technology and information read/write heads: In addition to magnetic tapes and disks, magnetic information recording devices include magnetic cards, magnetic ink record books, and magnetic records on banknotes, creating huge demand for magnetic information storage and readout sensors. Inductive heads, thin-film magnetoresistive heads, and amorphous heads are widely used. With the increase in recording density, for example, up to 100G bytes, heads with higher sensitivity and spatial resolution are required. Giant magnetoresistive heads based on multilayer metal films, amorphous alloy heads made from amorphous alloy wires, and giant magneto-impedance heads are engaging in intense competition. 5) Automotive industry: A large number of motors are used in automobiles (advanced cars require about 40 to 60 motors per vehicle, and ordinary cars have 15 motors; these motors show a trend towards brushless designs). The extensive use of magnetic sensors in them is self-evident. Another area with extensive use of magnetic sensors is the car's ABS system (Anti-lock Braking System), where an average of 4 to 6 speed sensors are used per car, mainly inductive speed sensors. New types of Hall gear sensors, which are gradually being promoted, as well as Wiegand devices, amorphous devices, and magnetoresistive devices, are about to enter this field. Additionally, there are speed sensors and igniters used for ignition timing in automotive engine systems. These areas also mainly use inductive sensors. Hall gear sensors and Hall plate switches are already used in some car models. According to Honeywell, by June 6, 1996, they had supplied 8000 ten thousand Hall vane switches and 300 ten thousand Hall gear speed sensors to the automotive industry. It is predicted that in the future, more than 30 magnetic sensors similar to Hall sensors will be adopted in a single car. Furthermore, in fields such as industrial automatic control, robotics, office automation, home appliances, and various security systems, in addition to the extensive use of brushless DC motors and AC variable frequency drives, a large number of magnetic temperature controllers are used in devices such as refrigerators, air conditioners, and rice cookers. By the mid-80s, the number had already exceeded hundreds of millions.

Weidou Intelligent Technology specializes in selling German PREH sensors, PREH proximity sensors, PREH distance sensors, PREH vision sensors, PREH displacement sensors, PREH torque sensors, PREH speed sensors, PREH photoelectric sensors, PREH position sensors, PREH angle sensors, PREH tactile sensors, PREH temperature sensors, PREH pressure sensors, PREH flow sensors, PREH level sensors, PREH motion sensors, PREH process sensors. Original German imports. Welcome inquiries and orders.