What is the operating principle of a pellet press, and how can its production efficiency be optimized?

　What is the working principle of a high-precision encoder?

　　Working principle and functions of a high-precision encoder: It is a rotary sensor that converts rotational displacement into a series of digital pulse signals. These pulses can be used to control angular displacement. When combined with a gear rack or a screw, a high-precision encoder can also measure linear displacement.

　　After a high‑precision encoder generates an electrical signal, it is processed by CNC systems, PLCs, control systems, and the like. These sensors are primarily used in the following applications: machine tools, material processing, motor feedback systems, and measurement and control equipment. In ELTRA’s high‑precision encoders, the photoelectric scanning principle is employed to convert angular displacement. The readout system relies on the rotation of a radial index disc composed of alternating transparent and opaque sectors. An infrared light source illuminates the disc perpendicularly, projecting the pattern onto the receiver surface, which is coated with a grating—known as a collimator—whose apertures correspond to those of the disc. The receiver detects the light‑intensity variations caused by the disc’s rotation and converts these optical changes into corresponding electrical signals. Typically, a rotating high‑precision encoder can also provide a speed signal, which should be fed back to the variable‑frequency drive to adjust its output parameters. Fault symptoms: 1. When the high‑precision encoder fails (no output), the VFD does not operate normally, and the speed slows down. Additionally, the VFD may enter a protective state, displaying “PG is off.” To elevate the electrical signal to a higher level and generate clean square‑wave pulses free from interference, electronic circuitry performs the necessary conditioning. The wiring and parameter settings between the encoder’s PG interface and the vector converter, as well as the connection method between the encoder’s PG and the PG card, must match the specific encoder model. Generally, encoder PG interfaces come in three types: differential output, open‑collector output, and push‑pull output. The signal transmission mode should take into account the VFD’s PG card interface; therefore, selecting the appropriate PG card type or configuring the settings accordingly is essential.

　　Encoders are generally classified into incremental and absolute types. The key difference is that, in an incremental encoder, position is determined by counting pulses from a reference mark, whereas in an absolute encoder, position is identified directly from the output code. In an absolute encoder, each unique position corresponds to a distinct output code; thus, even when power is lost, the encoder retains its position information. Upon power restoration, the position reading remains valid—unlike an incremental encoder, which requires re‑establishing the reference mark.

　　Currently, encoder manufacturers offer a wide range of products, many of which are application‑specific, such as encoders for elevators, machine tools, and servo motors. In addition, these encoders are intelligent and feature various parallel interfaces that enable communication with other devices. An encoder is a device that converts angular or linear displacement into an electrical signal; the former is referred to as an optical disk, while the latter is called an optical scale. Based on the readout method, encoders can be classified as either contact-type or non-contact-type.