A tachometer is one of the essential instruments in the mechanical industry, used to measure the speed, linear speed, or frequency of a motor. Commonly used in manufacturing industries such as electric motors, fans, papermaking, plastics, chemical fibers, washing machines, automobiles, airplanes, ships, etc. Most commonly used are handheld centrifugal tachometers. Tachometer measurement is essential in various fields of the national economy.

Tachometers include centrifugal tachometers, magnetic tachometers, electric tachometers, magneto electric tachometers, flash tachometers, electronic tachometers, and other types.

The centrifugal tachometer uses the balance between centrifugal force and tensile force to indicate the speed. Centrifugal tachometer is a traditional speed measurement tool, which is a mechanical tachometer that utilizes the principle of centrifugal force; The measurement accuracy is generally between 1-2 levels, and it is generally installed on site. A good centrifugal tachometer not only has the characteristics of accuracy and intuitiveness, but also has the advantages of reliability and durability. But the structure is quite complex.

The magnetic tachometer uses a rotating magnetic field to generate a rotational force on the metal cap, and uses the balance between the rotational force and the hairspring force to indicate the speed. A magnetic tachometer is a model of successfully utilizing magnetic force and is a mechanical tachometer that utilizes the principle of magnetic force; Generally installed on site, flexible shafts can be used for short distance remote installation. Magnetic tachometer, due to its simple structure, is currently widely used in motorcycles, cars, and other mechanical equipment. The flexible shaft is prone to damage during remote installation.

The electric tachometer consists of a small AC generator, a cable, an electric motor, and a magnetic meter head. A small AC generator generates AC current, which is transmitted through cables to drive a small AC motor. The speed of the small AC motor is consistent with the speed of the measured shaft. The magnetic tachometer is coaxially connected to a small AC motor, and the speed indicated by the magnetic tachometer is naturally the speed of the measured shaft; Electric speed, very convenient for remote installation, good vibration resistance, widely used in diesel engines and ship equipment.

The magneto electric tachometer is a combination of a magneto electric sensor and an ammeter, making it very convenient to install in different locations.

The flash tachometer utilizes the principle of visual persistence. A flash tachometer, in addition to detecting rotational speed (reciprocating speed), can also observe the static image of objects in circular motion. It is an essential observation tool for understanding the working status of mechanical equipment.

Electronic tachometer is a relatively general concept: a speed measurement tool designed and manufactured based on modern electronic technology. It usually has sensors and displays, and some also have signal output and control. Due to the diversity of sensors and display devices, as well as the diversity of measurement methods, it is difficult to classify them like the first five. Here, electronic tachometers are classified separately from sensors and secondary instruments. If divided by installation and usage methods, there are also on-site installation, desktop, cabinet mounted, portable, and handheld.