【2026 Basic Knowledge】Complete Classification of Automated Instruments

1. Flow meters 【Purpose of the instrument】Flow meters are used to accurately measure the instantaneous and cumulative flow rates of liquids, gases, steam, slurries, and other fluids in pipelines. They are essential instruments for production measurement, energy consumption tracking, material mixing, and trade settlement. Flow meters based on different principles are suitable for various medium conditions, and can meet various requirements such as high temperature, high pressure, viscous fluids, the presence of impurities, and high-precision measurement. They are widely used in industrial applications such as water supply and drainage, gas transmission, chemical fluids, thermal steam, and slurry transportation. 1. Mass flow rate types: general mass flow meters, Coriolis mass flow meters, thermal mass flow meters. 2. Positive-displacement flow meters: gear flow meters, worm gear flow meters, and epicyclic gear flow meters. 3. Velocity-type flow meters: rotameter, ultrasonic flow meter, turbine flow meter, electromagnetic flow meter, vortex flow meter. 4. Differential pressure flow meters: orifice plate flow meters, nozzle flow meters, Venturi tube flow meters, elbow flow meters, V-cone flow meters, pitot tube flow meters, uniform velocity tube flow meters, wedge flow meters. 5. Other flow meters: orifice plate flow meters, open-channel flow meters, target flow meters, flow switches.

2. Level gauges 【Purpose of the instruments】Level gauges are the most commonly used primary measurement devices in industrial storage tanks, reaction vessels, and silos. They are primarily used to monitor the level and quantity of liquids, solid particles, and powders, enabling real-time monitoring of materials, prevention of overflow and vacuum conditions, as well as automatic control of material feeding and discharging. They are widely used in chemical storage tanks, water treatment tanks, grain and oil silos, coal powder storage bins, pharmaceutical reaction vessels, and other similar applications. It is divided into two main categories: continuous real-time measurement and fixed-point switch alarms, meeting the needs for accurate measurement and safety interlock control. 1. Continuous level measurement instruments (real-time value monitoring): direct-reading level gauges, capacitive level gauges, float level gauges, float-steel-belt level gauges, magnetic flip-board level gauges, servo level gauges, barrel level gauges, magnetostrictive level gauges, fiber-optic level gauges, laser level gauges, ultrasonic level gauges, radar level gauges, external measurement level gauges, gamma-ray level gauges, differential pressure level gauges, weight-type level gauges. 2. Fixed-point level switches (high/low level alarm/start/stop control): capacitive level switches, float level switches, fork-type level switches, vane type level switches, ultrasonic level switches, external measurement level switches, radio frequency admittance level switches, electromagnetic level switches, electronic level switches, photoelectric level switches.

3. Pressure instruments 【Purpose of instruments】Pressure is one of the four key parameters in industrial processes. Pressure instruments are used to measure gauge pressure, absolute pressure, differential pressure, and vacuum levels in pipes, equipment, and containers. They enable real-time monitoring of the stress conditions on equipment and the operating load on pipes, thus helping to prevent safety incidents such as overpressure explosions, collapse due to negative pressure, and pipe leakage. It is widely used in applications such as the petrochemical industry, pressure vessels, thermal pipelines, hydraulic and pneumatic equipment, and vacuum systems, and serves as a key monitoring instrument for the safe operation of equipment. Liquid column pressure gauges, piston pressure gauges, elastic pressure gauges, electric remote transmission pressure meters, Hall effect pressure sensors, strain gauge pressure sensors, piezoresistive pressure sensors, torque-balanced pressure transmitters, capacitive pressure transmitters, Bourdon tube pressure gauges, diaphragm box pressure gauges, bellows-type pressure gauges.

4. Temperature Instruments 【Purpose of Instruments】Temperature instruments are used for collecting and monitoring the temperature of media, equipment, furnaces, and pipelines in industrial production. They fall into two categories: contact-type precise temperature measurement and non-contact-type high-temperature measurement. It enables automatic control of heating, cooling, and constant-temperature processes, effectively ensuring the stability of the reaction process, preventing equipment damage due to overheating, and avoiding spoilage of the materials. It is widely used in industries such as kilns, heat treatment, chemical reactions, power boilers, food sterilization, and low-temperature cold chains. Bimetallic thermometers, pressure-type thermometers, resistance-type thermometers (thermistor thermometers), thermocouple thermometers, glass tube liquid thermometers, temperature transmitters, temperature switches, optical/radiation pyrometers, contactless infrared temperature detectors.

5. Gas analysis instruments 【Purpose of the instruments】Gas analysis instruments are primarily used for online detection of the components, concentration, and purity of environmental gases and process gases; they also serve to ensure explosion protection in workshops and to monitor leaks of toxic and harmful gases. It enables real-time analysis of the components of oxygen, flammable gases, toxic gases, and process mixtures, and is used for process purification, exhaust gas monitoring, ensuring safety and explosion prevention in workshops, as well as detecting emissions to meet environmental standards. It is an essential safety device for industries such as chemicals, coal chemistry, gas processing, environmental protection, and mining. Gas chromatography/mass spectrometry analyzer, oxygen analyzer, toxic/flammable gas detector, thermal conductivity analyzer, magnetic permeability (force) analyzer, electrochemical gas analyzer, infrared analyzer, ultraviolet analyzer, laser gas analyzer, photoelectric detection gas analyzer.

6. Liquid analysis instruments 【Purpose of the instruments】Liquid analysis instruments are designed for detecting the physical and chemical properties, composition, purity, and level of contamination in liquid media, and they are used in both water quality monitoring and the analysis of chemical liquids. It primarily measures key parameters such as pH, conductivity, turbidity, dissolved oxygen, residual chlorine, COD, BOD, viscosity, and density. It is widely used in areas such as municipal wastewater treatment, pure water production, chemical distillation, oil product testing, environmental monitoring systems, and pharmaceutical pure water systems. Electrochemical liquid analyzers, UV-Vis spectrophotometers, infrared absorption spectrometers, distillation range analyzers, liquid chromatography/mass spectrometry analyzers, viscometers, densitometers, water quality analyzers, pH meters, conductivity meters, concentration meters, turbidity meters, dissolved oxygen analyzers, residual chlorine analyzers, BOD/COD analyzers.

7. On-site control instruments 【Purpose of the instruments】On-site control instruments are devices used for local operation; they rely on three types of power sources – pneumatic, hydraulic, and electric – to enable local manual/automatic control of valve opening and closing, pressure regulation, flow control, and temperature adjustment. It plays a key role in scenarios without a remote control system, where individual sections are controlled independently, or in emergency manual operation in case of failures; it is the basic control unit that enables on-site adjustment of equipment and ensures the continuous operation of the process. Pneumatic control instruments, hydraulic control instruments, electric control instruments.

8. Display and recording instrument 【Purpose of the instrument】 The display and recording instrument is a key device for human-computer interaction and data retention; it is responsible for converting analog signals such as temperature, pressure, flow rate, and level measured on-site into visible data, while also handling data storage, curve recording, and over-limit alarms. It enables maintenance personnel to view operating conditions in real time, retrieve historical data, diagnose faults, and keep production records, making it suitable for use in scenarios such as on-site display in workshops, data monitoring in control rooms, and tracking of production data. Paper recorders, paperless recorders, flash alarms, displays, analog display instruments, digital display instruments, HMIs, and CRT display terminals.

9. Control instruments and systems 【Purpose of instruments】The control system serves as the \"brain\" of an automated production line, responsible for the centralized collection of data from the entire plant and all workstations, performing logical operations, enabling automatic adjustments, providing interlock protection, and allowing remote control. Ranging from small-scale single-loop PID control and PLC programming to large-scale DCS distributed control, SIS safety interlocks, and ESD emergency shutdown systems, it covers all aspects of conventional production control as well as safety protection in high-risk operating conditions; it is the core system behind the automated, intelligent, and unmanned operation of modern factories. PID controllers, PLC programmable logic controllers, digital control systems, IPC industrial computers, alarm interlock control systems, DCS distributed control systems, FCS fieldbus control systems, ESD emergency shutdown systems, SIS safety instrumented systems.

10. Special measuring instruments 【Purpose of the instruments】Special measuring instruments are designed to measure parameters under specific operating conditions that cannot be detected by conventional instruments; they are primarily used in the maintenance of large-scale moving equipment, precision testing, instrument calibration, and monitoring of combustion conditions. It is widely used for the condition monitoring of rotating equipment such as turbines, fans, and pumps, for the weighing and measurement of industrial materials, for the detection of sheet metal thickness, for the calibration of instruments, and for the monitoring of furnace flames, thereby ensuring the stable operation of large-scale equipment and maintaining control over production accuracy. Axial vibration meter, axial displacement meter, shaft speed meter, weight measuring (control) instrument, thickness meter, signal generator (calibration) instrument, flame detector.