German HOHNER encoder HOHNER model HOHNER price

HOHNER encoder is a sensor that converts mechanical geometric displacement on the output shaft into pulses or digital quantities through photoelectric conversion. It is currently the most widely used sensor. Photoelectric encoders consist of a light source, a code disk, and photosensitive elements. The grating disk has several rectangular openings evenly distributed on a circular plate of a certain diameter. Since the photoelectric code disk is coaxial with the motor, when the motor rotates, the grating disk rotates at the same speed as the motor. A detection device composed of electronic components such as light-emitting diodes detects and outputs several pulse signals. By calculating the number of pulses output by the photoelectric encoder per second, the current speed of the motor can be reflected. In addition, to determine the direction of rotation, the code disk can also provide two pulse signals with a phase difference of 90º.

HOHNER encoder device requirements

1. Requirements for CNC machine tools regarding detection elements and position detection devices (1) Requirements for CNC machine tools regarding detection elements: Detection elements are important components of detection devices. Their main function is to detect displacement and speed, and send feedback signals. The minimum displacement that a displacement detection system can measure is called resolution. Resolution depends not only on the detection element itself but also on the measurement circuit. The main requirements for detection elements in CNC machine tools are: (1) long service life, high reliability, and strong anti-interference capability; (2) meeting precision and speed requirements; (3) easy to use and maintain, suitable for the machine tool operating environment; (4) low cost; (5) easy to connect to computers. Different types of CNC machine tools have different requirements for the precision and speed of the detection system. Usually, large CNC machine tools primarily focus on meeting speed requirements, while medium, small, and high-precision CNC machine tools primarily focus on meeting precision requirements. When selecting the resolution and pulse equivalent of the measurement system, it is generally required to be one order of magnitude higher than the machining precision. (2) Requirements for CNC machine tools regarding position detection devices: Position detection devices are an important part of the servo system of CNC machine tools. Their function is to detect displacement and speed, send feedback signals, and form closed-loop or semi-closed-loop control. The machining precision of CNC machine tools is mainly determined by the precision of the detection system. Different types of CNC machine tools have different requirements for the precision of position detection elements and detection systems, as well as the maximum moving speed of the measured components. The highest level of detection elements and systems is: when the maximum moving speed of the measured component is up to 240m/min, the resolution of displacement detection (the minimum detectable displacement) can reach 1μm; for example, at 24m/min, it can reach 0.1μm. The highest resolution can reach 0.01μm. CNC machine tools have the following requirements for position detection devices: (1) minimal influence from temperature and humidity, reliable operation, ability to maintain precision over long periods, and strong anti-interference capability. (2) capable of meeting precision and speed requirements within the movement range of the machine tool's executing components. (3) easy to use and maintain, adaptable to the machine tool working environment. (4) low cost. Introduction to spindle encoders 2. Classification of position detection devices For different types of CNC machine tools, due to different working conditions and detection requirements, the following different detection methods can be adopted. (1) Incremental and absolute measurement Incremental detection methods only measure displacement increments and use the number of digital pulses to represent the quantity of unit displacement (i.e., the minimum setting unit). A measurement signal is issued for every movement of one measurement unit. Its advantage is that the detection device is relatively simple, and any centering point can serve as the starting point for measurement. However, in this system, the displacement is read out after accumulating the measurement signals. Once there is an accumulation error, all subsequent measurement results will be incorrect. Additionally, in the event of a fault (such as power loss), the correct position before the accident cannot be found. After the fault is cleared, the worktable must be moved to the starting point to recount in order to find the correct position before the accident. Pulse encoders, resolvers, induction synchronizers, gratings, magnetic scales, laser interferometers, etc., are all incremental detection devices. Absolute measurement methods measure the absolute coordinate position value of the measured component in a certain absolute coordinate system, and express it in binary or decimal digital signals. Generally, it needs to be converted into pulse digital signals before being sent for comparison and display. With this method, the higher the resolution requirement, the more complex the structure. Such measurement devices include absolute pulse code disks, three-speed absolute code disks (also known as multi-turn absolute code disks), etc. (2) Digital and analog measurement Digital detection quantifies the measured unit and expresses it in digital form. The measurement signal is generally an electrical pulse, which can be directly sent to the numerical control system for comparison and processing. Such detection devices include pulse encoders and gratings. Digital detection has the following 3 characteristics. (1) The measured quantity is converted into the number of pulses, facilitating display and processing; (2) Measurement precision depends on the measurement unit and is basically independent of the range; however, cumulative code errors exist; (3) The detection device is relatively simple, and pulse signals have strong anti-interference capability. Analog detection represents the measured quantity using continuous variables, such as changes in voltage amplitude, phase changes, etc. Precise analog detection over a large range imposes high technical requirements. In CNC machine tools, analog detection is mainly used for small-range measurements. Analog detection devices include tachogenerators, resolvers, induction synchronizers, and magnetic scales. The main characteristics of analog detection are as follows. (1) Direct detection of the measured quantity without quantization. (2) High-precision measurement can be achieved within a small range. (3) Capable of direct and indirect detection. Position detection devices installed on executing components (i.e., end pieces) to directly measure the linear or angular displacement of the end pieces of the executing components are called direct measurement, which can form a closed-loop feed servo system.Measurement methods include linear gratings, linear induction synchronizers, magnetic scales, laser interferometers, etc., to measure the linear displacement of executing components. Since this detection method uses linear detection devices to measure the linear displacement of the machine tool, its advantage is that it directly reflects the linear displacement of the worktable. The disadvantage is that the detection device is required to be as long as the travel distance, which is a significant limitation for large machine tools. Position detection devices installed on transmission elements in front of the executing components or on the drive motor shaft measure angular displacement. The linear displacement of the executing components is obtained after transformation through the transmission ratio. This is called indirect measurement, which can form a semi-closed-loop servo feed system. For example, mounting a pulse encoder on the motor shaft. Indirect measurement is reliable and convenient to use, with no length limitations. Its disadvantage is that the transmission chain error from converting linear motion to rotary motion is added to the detection signal, thereby affecting measurement precision. Generally, compensation for the machine tool's transmission error is required to improve positioning precision. In addition to the above position detection devices, servo systems often include speed detection elements to detect and adjust the engine speed. The commonly used speed detection element is the tachogenerator.

HOHNER encoder main functions

It is a rotary sensor that converts rotary displacement into a series of digital pulse signals. These pulses can be used to control angular displacement. If the encoder is combined with a rack and pinion or a lead screw, it can also be used to measure linear displacement. After the encoder generates electrical signals, they are processed by numerical control devices CNC, programmable logic controllers PLC, control systems, etc. These sensors are mainly applied in the following areas: machine tools, material processing, motor feedback systems, and measurement and control equipment. In ELTRA encoders, the conversion of angular displacement adopts the principle of photoelectric scanning. The reading system is based on the rotation of a radial graduated disk, which consists of alternating transparent and opaque windows. The entire system is illuminated vertically by an infrared light source, so that the light projects the image on the disk onto the surface of the receiver. The receiver is covered with a grating, called a collimator, which has the same windows as the code disk. The receiver's job is to sense the light changes produced by the rotation of the code disk and then convert these light changes into corresponding electrical changes. Generally, a rotary encoder can also obtain a speed signal, which is fed back to the frequency converter to adjust the output data of the frequency converter. Fault phenomena: 1. When the rotary encoder is faulty (no output), the frequency converter cannot operate normally, the running speed becomes very slow, and the frequency converter protection activates after a while, displaying "PG disconnected"... Joint action is required for it to function. To raise the electrical signal to a higher level and generate square wave pulses without any interference, electronic circuits must be used for processing. The pg wiring of the encoder and the connection method between the vector frequency converter and the encoder pg must correspond to the model of the encoder pg. Generally, encoder pg models are divided into three types: differential output, open collector output, and push-pull output. The signal transmission method must consider the interface of the frequency converter pg card, so choosing the appropriate pg card model or setting it reasonably is necessary. Encoders are generally divided into incremental and absolute types, with the biggest difference being: in the case of incremental encoders, the position is determined by the number of pulses counted from the zero mark, while the position of absolute encoders is determined by the reading of the output code. Within one revolution, the reading of the output code for each position is unique; therefore, when the power is disconnected, the absolute encoder does not lose track of the actual position. If the power is connected again, the position reading remains current and valid; unlike incremental encoders, there is no need to search for the zero mark. Encoder manufacturers produce comprehensive series, which are generally specialized, such as elevator-specific encoders, machine tool-specific encoders, servo motor-specific encoders, etc. Furthermore, encoders are intelligent and have various parallel interfaces to communicate with other devices. An encoder is a device that converts angular displacement or linear displacement into electrical signals. The former is called a code disk, and the latter is called a code scale. According to the reading method, encoders can be divided into contact and non-contact types. Contact types use brush output, where a brush contacts a conductive area or an insulating area to indicate whether the code status is "1" or "0"; non-contact types use photosensitive or magnetosensitive elements as receiving sensitive components. When using photosensitive elements, transparent and opaque areas indicate whether the code status is "1" or "0". According to the working principle, encoders can be divided into incremental and absolute types. Incremental encoders convert displacement into periodic electrical signals, and then convert these electrical signals into counting pulses, using the number of pulses to represent the magnitude of displacement. Each position of an absolute encoder corresponds to a definite digital code, so its indication value is only related to the starting and ending positions of the measurement, and not to the intermediate process of the measurement. Rotary incremental encoders output pulses during rotation, and their position is known through counting equipment. When the encoder is stationary or powered off, it relies on the internal memory of the counting equipment to remember the position. Thus, after a power outage, the encoder must not move. When power is restored and the encoder outputs pulses, there must be no interference causing pulse loss; otherwise, the zero point remembered by the counting equipment will shift, and the amount of this shift is unknown until erroneous production results appear. The solution is to add a reference point. Every time the encoder passes the reference point, the reference position is corrected into the memory position of the counting equipment. Before the reference point, the accuracy of the position cannot be guaranteed. Therefore, in industrial control, there are methods such as finding the reference point before each operation and finding zero upon startup. Such encoders are determined by the mechanical position of the code disk and are not affected by power outages or interference. Absolute encoders determine the uniqueness of each position by mechanical position. They do not require memory, do not need to find a reference point, and do not need to count continuously. Whenever the position needs to be known, its position is read. Thus,the anti-interference characteristics of the encoder and the reliability of the data are greatly improved. Since absolute encoders are significantly superior to incremental encoders in positioning, they are increasingly used in industrial control positioning. Due to the high precision of absolute encoders and the large number of output bits, if parallel output is still used, the connection of each bit of output signal must be ensured to be very good. For more complex working conditions, isolation is also required, resulting in many cable cores, which brings considerable inconvenience and reduces reliability. Therefore, for multi-bit output types, absolute encoders generally select serial output or bus-type output. The most common serial output for absolute encoders produced in Germany is SSI (Synchronous Serial Interface). Multi-turn absolute encoders. Encoder manufacturers apply the principle of clock gear mechanics. When the central code disk rotates, another set of code disks (or multiple sets of gears and code disks) is driven through gear transmission. Based on single-turn encoding, the encoding of the number of turns is added to expand the measurement range of the encoder. Such absolute encoders are called multi-turn absolute encoders. They are also determined by mechanical position, with unique and non-repeating encoding for each position, requiring no memory. Another advantage of multi-turn encoders is that due to the large measurement range, there is often considerable margin in actual use. Thus, during installation, it is not necessary to struggle to find the zero point; a certain intermediate position can be used as the starting point, greatly simplifying the difficulty of installation and debugging. Multi-turn absolute encoders have obvious advantages in length positioning and are increasingly used in industrial control positioning.

HOHNER encoder applications

Textile machinery, irrigation machinery, papermaking and printing, water conservancy gates, robots and robotic arms, port lifting machinery, steel and metallurgical equipment, heavy machinery, precision measurement equipment, machine tools, food machinery, elevators, and other special equipment.

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