Regarding level gauges

They’re different in principle! RF admittance level control technology measures the level by using high-frequency radio waves to determine the admittance of the medium being measured. In radio frequency admittance, admittance refers to the reciprocal of impedance in electricity, while radio frequency denotes the transmission of high-frequency radio waves. Guided wave radar level gauges measure the level by determining the time interval between the transmitted pulses and the reflected pulses. There’s no need to explain this! These are just my personal opinions for reference only!

Radio frequency admittance level gauge: A level control technology that evolved from capacitive level control techniques; it offers better resistance to material accumulation, greater reliability in operation, more accurate measurements, and broader applicability. In the term “radio frequency admittance,” “admittance” refers to the reciprocal of impedance in electricity, which is composed of resistive, capacitive, and inductive components. “Radio frequency” denotes high frequencies; thus, radio frequency admittance technology can be understood as a method of measuring admittance using high-frequency currents. The high-frequency sine oscillator provides a stable measurement signal source; by utilizing the bridge principle, it enables accurate measurement of the admittance of the sensor installed in the container to be measured. In direct-acting mode, the output of the instrument increases as the level of the liquid rises. Guided wave radar level gauge: It utilizes TDR (Time-Domain Reflection) technology; high-frequency narrow pulses are sent along a rod or cable, and when they encounter a surface of a medium with a higher dielectric constant than the previous conducting medium (air or vapor), the pulse waves are reflected back. A super-high-speed timing circuit is used to calculate the propagation time of pulse waves; through precise calculations, accurate measurement of the liquid level can be achieved.

Information on several types of level gauges has been collected for reference only. Magnetic flap level gauge – Main principle: The magnetic flap level gauge, also known as a magnetic float level gauge, is designed and manufactured based on the principles of buoyancy and magnetism. The position of a float with magnets (referred to as a magnetic float) in the medium being measured is influenced by buoyancy. Changes in the liquid level cause changes in the position of the magnetic float; the electrostatic magnetic force interaction between the magnetic float and the magnetic flip bars (also known as magnetic switches) causes these flip bars to rotate by a certain angle (the surfaces of the flip bars are painted in different colors), thereby indicating the liquid level inside the container. Electronic modules and transmitter modules composed of sensors (reed switches) and precision electronic components can transmit signal values of resistance, current values (4–20 mA), switch signals, as well as other electrical signals. Thus achieving a perfect combination of on-site observation and remote control. Scope of Application and Features: This level gauge uses high-quality magnets and imported electronic components, giving it advantages such as a rational design, simple structure, ease of use, stable performance, long service life, and convenience for installation and maintenance. This level gauge provides a variety of output signals, enabling remote indication, detection, control, and recording of liquid levels. This level gauge can be applied to liquid level measurement and control in various industrial automation process controls. It can be widely used in fields such as oil processing, food processing, chemicals, water treatment, pharmaceuticals, power generation, papermaking, metallurgy, ships, and boilers for level measurement, control, and monitoring. The basic principle of the magnetic floating ball level gauge (level switch) is that its structure is designed and manufactured based on the principles of buoyancy and a static magnetic field. The position of the float with a magnet (referred to simply as the float) in the medium being measured is influenced by buoyancy; changes in liquid level cause changes in the position of the magnetic float. The magnet and sensor (reed switch) inside the float cause the number of components connected in series in the circuit (such as fixed resistors) to change, which in turn alters the electrical parameters of the instrument’s circuit system. In other words, it is the change in the position of the magnetic float that causes a change in electrical quantities. The level of liquid inside the container is indicated by detecting changes in electrical quantities. This level gauge can directly output a resistance value signal, or it can be used in conjunction with a transmission module to output a current value (4–20 mA) signal ； It can also be used in conjunction with other converters to generate voltage signals or switch signals (the company can supply the converters as per customer requirements). Thereby enabling the remote transmission, analysis, and control of electrical signals. Scope of application and features: This product uses high-quality magnets and imported electronic components, giving it advantages such as a simple structure, ease of use, stable performance, a long service life, and simplicity in installation and maintenance. This product can be applied to liquid level measurement and control in various industrial automation process controls, and it is widely used for liquid level measurement, control, and monitoring in fields such as oil processing, food processing, chemicals, water treatment, pharmaceuticals, power generation, papermaking, metallurgy, shipbuilding, and boilers. Main principle of the explosion-proof float level switch: The explosion-proof float level switch is also known as an explosion-proof float level controller. It is a level control instrument specifically designed and manufactured for use in explosive environments. This product is based on the principles of buoyancy and levers; when the liquid level in the container changes, the position of the float changes accordingly. This movement of the float acts on a microswitch through the lever, which in turn generates a switch signal. Scope of Application and Features: This product is made from high-quality materials and imported electronic components, giving it advantages such as a rational design, simple structure, ease of use, stable performance, long service life, and convenience for installation and maintenance. Additionally, this instrument outputs switch signals, enabling remote level alarm and control. The high-temperature and high-pressure explosion-proof float level switch utilizes high-quality magnets and the principle of magnetic coupling to prevent electronic components from coming into direct contact with high-temperature media, thereby ensuring complete isolation between the high-pressure medium and these electronic components. The manufacturing of this product complies with relevant standards, and it has been approved by the Electrical Product Explosion Protection Quality Supervision and Inspection Center. The product can be widely used in industries such as petroleum, chemicals, power generation, metallurgy, food processing, pharmaceuticals, and papermaking. It enables braking alarms and control of the liquid level in various types of containers. Working Principle and Structure of Glass Plate Level Gauges: This level gauge is designed based on the principle of a communicating vessel. The liquid pathway, which consists of a glass plate and the main body of the level gauge, is connected to the container being measured through flanges or tapered pipe threads, thereby forming a communicating vessel. The liquid level visible through the glass plate corresponds to the liquid level inside the container, and this represents the level height. The needle valves at both ends of the level gauge not only serve as shut-off valves; the steel balls inside them also function as check valves. In the event that the level gauge is accidentally damaged and starts leaking, the steel balls can automatically close the liquid flow path under the pressure of the fluid, thereby preventing excessive leakage and providing a safety mechanism. Level gauges can achieve functions such as corrosion resistance, heat insulation, frost prevention, and lighting by changing the material of their components or adding additional parts. Scope of application and features: This product is made from high-quality quartz glass sheets, offering excellent performance. In addition, this product features a simple structure, cost-effectiveness, easy installation, reliable performance, and a long service life. As a basic level-indicating gauge, this product is widely used for measuring and monitoring liquid levels in the simplest level measurement applications as well as in large-scale engineering projects with a moderate level of automation. Principle of operation and structure of glass tube level gauges: Level gauges are designed based on the principle of a communicating vessel, consisting of a liquid passage made of glass tubes. The channel is connected to the container under test via a coupling flange or tapered pipe threads, forming a communicating vessel; the liquid level, which is the height of the liquid, corresponds to the liquid level observed through the glass tube. A tubular level gauge mainly consists of a glass tube, a protective sleeve, upper and lower valves, and connection flanges (or threads), etc. By changing the material of the parts in the level gauge or adding some auxiliary components, it is possible to achieve corrosion resistance or thermal insulation. Scope of application and features: This product uses high-quality quartz glass tubes, which possess excellent properties such as resistance to high temperatures and pressures. In addition, it has advantages such as simple structure, cost-effectiveness, easy installation, reliable operation, and a long service life. As a basic level-indicating gauge, this product is widely used for measuring and monitoring liquid levels in the simplest level measurement applications as well as in large-scale engineering projects with a moderate level of automation. Working principle of the steel strip level gauge: The steel strip level gauge is a traditional type of level gauge. It is designed and manufactured using the principles of mechanical equilibrium. It is composed of a level detection device, a high-precision displacement transmission system, a constant force device, a display device, a transmitter device, and other peripherals. The float submerged in the liquid being tested is subjected to gravity W, buoyancy F, and a constant pulling force T generated by a constant-force device; when the vector sum of these three forces is zero, the float is in a state of quasi-equilibrium at rest. At mechanical equilibrium, the buoyant force is quasi-constant (the volume V of the float submerged in the liquid remains constant). When the liquid level changes, the original mechanical equilibrium is disrupted by the buoyant force acting on the float, and a new equilibrium is achieved through the movement of the steel strip. The level detection device (float) moves the steel belt in response to the liquid level; the displacement transmission system causes the transmission pin to rotate through the movement of the steel belt, which in turn acts on the counter to display the liquid level. The transmitter converts this liquid level condition into a standard electrical signal, which is then transmitted via the signal line. This electrical signal can drive other control devices. Scope of application and features: This level gauge boasts practicality, a wide measurement range, high precision and stable performance, a long service life, and ease of maintenance. Additionally, a large counter display ensures clear and accurate readings ； Manual float lifting mechanism, allowing for regular inspection of the instrument’s performance ； It can be connected to various transmitters to form a level detection system. It can be widely used in various industries such as petroleum, chemicals, power generation, metallurgy, environmental protection, and food processing, as well as in associated facilities, for connecting transmitters. It converts changes in liquid level within containers into analog signals, electrical pulse signals, or switch signals, which are then transmitted to control rooms for display or to computer rooms for data presentation and processing. Principle of operation of the weight-based level gauge: The weight-based level gauge is designed and manufactured based on the principle of mechanical equilibrium. When the steel strip remains stationary at a certain position in the liquid, the gravity acting on the float, steel wire rope (or steel strip), weight, and pointer is in balance with the buoyant force exerted by the liquid on the steel strip and the frictional forces within the system. When the liquid level changes, the buoyant force F will change as well; the original equilibrium of the system is disturbed, and it will reach a new dynamic equilibrium. Changes in the liquid level cause the float’s position to change, and the weight drives the pointer up and down, allowing for a clear and intuitive display of the changes in the liquid level inside the container on the scale. The top of the scale plate indicates the zero level of the liquid surface, while the bottom indicates the full scale of the liquid surface. The pointer changes as the liquid level changes, thereby continuously indicating the height of the liquid level. Scope of application and features: It can be widely used in fields such as chemicals, power generation, and water treatment for the continuous measurement of liquid levels in medium and large-sized storage tanks, including various types of liquids as well as highly viscous and corrosive liquids, under normal pressure conditions. Working principle of ultrasonic level gauge: The working principle of this product is as follows: A device that can emit energy waves (usually pulse signals) is used to send out such waves; when these waves encounter an obstacle, they are reflected, and a receiving device captures the reflected signals. The level change is determined based on the time difference measured during the movement of the energy wave. The electronic device processes the microwave signal, ultimately converting it into an electrical signal related to the level of the substance. The probe emits ultrasonic pulse signals toward the surface of the medium being measured. As these ultrasonic waves travel and encounter the medium (an obstacle), they are reflected. The reflected ultrasonic signals are detected by an electronic module and processed using specialized software. By analyzing the time difference between the emitted ultrasonic waves and the echoes, and taking into account the speed of sound propagation, it is possible to accurately calculate the distance that the ultrasonic waves have traveled, thereby determining the level of the substance. Scope of application and features: The microprocessor unit in the electronic module of this product possesses strong analytical capabilities, which enable it to optimize legitimate echoes and eliminate erroneous or false ones, thereby yielding accurate values. At the same time, this product features stable performance, low cost, and high precision. It has the capability to output analog, digital, and switch signals simultaneously, and comes with a waterproof casing, making it suitable for liquid level detection in various general applications. Its main chip is a Philips industrial-grade single-chip microcomputer, along with digital temperature compensation and related dedicated integrated circuits; it boasts strong interference resistance. It allows for the arbitrary (custom) setting of upper and lower limits as well as online output adjustment, and it features on-site display, analog and digital outputs, enabling easy connection to a host computer. In addition, this product uses a professional ultrasonic small-angle probe with high transmission power, high sensitivity, long service life, and a long measurement range ； Setting of upper and lower limits for any point, as well as setting of inverse values. It can be used for automatic compensation for disturbances caused by steam, dust, and moisture. It can be applied not only to liquids/solids but also for continuous material/level control in tanks, reservoirs, storage areas for continuous material/level measurement, grain silos, and similar applications. It is widely used in industries such as petroleum, chemicals, tap water, sewage treatment, hydrology and water resources, steel, coal mining, electricity, transportation, and food processing. Main principle of intelligent radar level gauge: An intelligent radar level gauge is a type of microwave level gauge that makes use of microwave (radar) positioning technology. It emits energy waves through a device that is capable of sending out such waves (usually in the form of pulse signals); when these energy waves encounter an obstacle, they are reflected, and a receiving device captures the reflected signals. The level change is determined based on the time difference measured during the movement of the energy wave. The electronic device processes the microwave signal, ultimately converting it into an electrical signal related to the level of the substance. In microwave level measurement devices, the energy waves used are typically high-frequency electromagnetic waves with a frequency of 8.3 GHz (mostly around 6 GHz, though higher frequencies are also used). The energy wave used by this device is a pulsed energy wave. The maximum pulse energy of a typical pulse energy wave is around 1 mW (with an average power of around 1 μW), and it does not cause any radiation damage to other devices or people. Scope of application and features: The intelligent radar level gauge is used for non-contact, continuous measurement of the level of liquids, slurries, and granular materials. It is suitable for applications with large temperature and pressure fluctuations, as well as those involving inert gases or steam. It uses a microwave pulse (PTOF) measurement method and can operate properly within the industrial frequency band. It has low beam energy, can be installed in various metal and non-metal containers or pipes, and causes no harm to humans or the environment. It features the following advantages: 1. No dead zones, high precision; 2. Two-wire technology, making it an excellent alternative to differential pressure instruments, magnetostrictive sensors, radio frequency admittance meters, and magnetic flap gauges. 3. Unaffected by changes in pressure, vacuum, temperature, inert gases, dust, steam, and other environmental factors. 4. Easy to install, durable, and maintenance-free. 5. The output signal is in the 4mA–20mA range according to the HART protocol; calibration is simple, and on-site calibration can be carried out easily via a digital LCD display. Simple configuration and programming are possible through software. 6. High measurement sensitivity and fast update speed. 7. Suitable for high-temperature operating conditions, with process temperatures up to 200°C; this value can reach 350°C when a high-temperature extension antenna is used. Working principle of the guided wave radar level gauge: The guided wave radar level gauge is a type of microwave level gauge that makes use of microwave (radar) positioning technology. It emits energy waves through a device capable of sending out such waves (usually in the form of pulse signals). These energy waves travel along waveguides; when they encounter obstacles, they are reflected. The reflected energy waves are then transmitted by the waveguides to the receiving device, which captures these reflected signals. The level change is determined based on the time difference measured during the movement of the energy wave. The electronic device processes the microwave signal, ultimately converting it into an electrical signal related to the level of the substance. The energy radiation level is low; the energy waves used by this device are pulse energy waves (with a frequency generally lower than that of smart radar level gauges). The maximum pulse energy of a typical pulse energy wave is around 1 mW (with an average power of around 1 μW), and it does not cause any radiation damage to other devices or people. Scope of application and features: The guided-wave microwave level gauge is used for continuous, contact-based measurement of media with a relatively low dielectric constant, such as liquids, slurries, and granular materials. It is suitable for environments with large temperature and pressure fluctuations, as well as those containing inert gases or steam. It has the following features: 1. High versatility: It can measure liquid levels as well as material levels, and can meet the measurement requirements for different temperatures, pressures, and media. The maximum measurement temperature is 800°C, and the maximum pressure is 5 MPa; it can also be used in harsh environments such as those with corrosive conditions or high impact forces. 2. Prevention of material buildup: The unique circuit design and sensor structure ensure that measurements are not affected by any material buildup on the sensor, eliminating the need for regular cleaning and preventing inaccurate readings. 3. Maintenance-free: There are no moving parts during the measurement process, so there is no risk of mechanical damage and no maintenance is required. 4. Anti-interference: As it is a contact-based measurement method, it has strong anti-interference capabilities and can overcome the effects of steam, foam, and stirring on the measurement. 5. Accurate and reliable: A variety of measurement options ensure higher accuracy; the measurements are not affected by environmental changes, offering high stability and a long service life. Working principle of capacitive level gauges: The measurement principle of capacitive level gauges is based on the fact that the oscillation frequency of an oscillating circuit is related to the capacitance value. Changes in the liquid level cause changes in the capacitance of the system, which in turn alters the oscillation frequency of the oscillating circuit. The oscillating circuit in the sensor can convert the changes in capacitance caused by variations in liquid level into frequency changes, which are then sent to the electronic module. After computational analysis and processing, these values are converted into measurable engineering units for display, thereby enabling continuous measurement of the liquid level. This instrument is manufactured using advanced technologies and production processes; it consists of sensors, secondary instruments, and other accessories. The sensor is placed on top of the silo, with the probe extending vertically into the silo; the secondary instrument is placed in some other suitable location. The sensor converts changes in liquid level into corresponding electrical pulse signals, which are transmitted to secondary instruments for processing and displaying the liquid level. It also provides high/low limit alarms as well as a 4–20mA output signal; it is suitable for displaying, alarming about, controlling the liquid level of liquid/solid materials, as well as for remote display or use within systems. Scope of application and features: This level gauge boasts the advantages of a simple structure, easy installation, and reliable performance ； Meanwhile, the electrodes are made of stainless steel, offering strong corrosion resistance; both insulating and conductive materials can be used, and maintenance requirements are low. This level gauge can be widely used in industrial sectors such as petroleum, chemicals, power, metallurgy, food, and environmental protection to monitor the liquid level in open or pressurized vessels. However, this level gauge is not suitable for applications where the dielectric constant or material humidity changes significantly, nor for solid media whose particle size is greater than 15 mm and thus cannot make good contact with the electrodes. Working Principle of Radio Frequency Admittance Level Controller: The radio frequency admittance level controller is a new type of level measurement instrument designed and manufactured using radio frequency admittance level control technology. RF admittance measurement technology, simply put, is a method that uses a high-frequency current measurement system to measure admittance. Point RF admittance technology differs from capacitance technology in that it employs a three-terminal approach, which enables a variety of measurement parameters. RF admittance technology improves the signal-to-noise ratio of the instruments by introducing measurement parameters other than capacitance, particularly resistance parameters, thereby significantly enhancing the resolution, accuracy, and reliability of the instruments ； The diversity of measurement parameters has also significantly expanded the reliable application areas of instruments. A level control technology that improves the product’s resistance to material adhesion (material adhering to sensors is referred to as adhesion), enhances reliability in operation, increases measurement accuracy, and broadens its applicability. This product is mainly composed of a sensor module, an electronic module, and some other connecting components. The sensor unit mainly consists of three parts: the measuring probe, the shield electrode, and the ground terminal. The height of the material being measured is reflected in the change in the admittance between the measuring probe and the container wall; when the material reaches the operating point of the switch, the electronic unit responds by activating the relay, thereby generating a switch signal. The shield electrode prevents false operation signals caused by residue on the electrodes, and only outputs a switch control signal when the material actually reaches the set point. Scope of application and features: The microwave level controller utilizes advanced radio frequency admittance technology, overcoming the drawback of capacitive level switches, which are unable to eliminate the influence of conductive deposits. It has the following features: 1. High versatility: suitable for various applications, capable of detecting particles, fly ash, conductive and non-conductive liquids, as well as viscous materials ； 2. Anti-adhesion circuit: An advanced anti-adhesion circuit design that eliminates material adhesion, thereby preventing false error signals from being generated ； 3. Power loss protection mode: Low or high fault alarm. Adjustable on-site. This level gauge operates reliably, with all its technical specifications meeting the standards of international counterparts; it is widely applicable for the detection and control of liquid levels, slurry levels, dust levels, as well as the interface between two different liquids. In addition, the product features an indication of the operating status on-site, making it a cost-effective, stable, and reliable level switch. Working principle of the tuning fork level controller: The tuning fork type level controller is a new type of level switch. It is designed and manufactured using the principle of tuning fork vibration. It is located at the base of the sensing rod of the tuning fork level switch; a piezoelectric crystal is used to drive the tuning fork rod, while another piezoelectric crystal detects the vibration signals, enabling these signals to be circulated and causing the sensing rod to resonate. When the material comes into contact with the induction rod, the vibration signal gradually decreases until resonance stops, at which point the control circuit outputs an electrical contact signal. Due to the natural principle that the sensitivity of the sensing rod decreases from the front end to the rear part, no error signals are generated when the material in the tank accumulates around it and touches the base of the sensing rod <at the rear> or during discharge. Simply put, a tuning fork generates mechanical vibrations when stimulated by a piezoelectric crystal, and these vibrations have a certain frequency and amplitude. When a tuning fork is submerged in a liquid or solid, its vibration frequency and amplitude change. This frequency change is detected by the electronic circuit and a digital signal is output. Scope of application and features: The tuning fork level switch is a new type of level switch. It is suitable for almost all liquid media, as well as for measuring moderately dense solid powders or particles that can flow freely. Since the tuning fork level switch has virtually no moving parts, there is little mechanical wear; as a result, it requires no maintenance or adjustment and is simple and easy to use. In addition, this level switch utilizes foreign advanced technologies and originally imported chips, offering advantages such as a long service life, stable performance, and reliability. It also features strong adaptability (the electrical parameters and density of different media being measured do not affect the measurement), no need for calibration (no on-site calibration is required regardless of the medium being measured), and maintenance-free operation. It is widely used in process control of liquid levels in industries such as metallurgy, building materials, chemicals, light industry, and food processing. Working principle of magnetostrictive level gauges: The working principle of magnetostrictive level sensors involves an initial pulse generated by the electronic circuitry within the electronic housing. As this initial pulse travels along the waveguide wire, it creates a rotating magnetic field that moves in the direction of the waveguide wire. When this magnetic field encounters the permanent magnetic field present in the magnetic ring or float, a magnetostrictive effect occurs, causing the waveguide wire to twist. This twisting motion is detected by a sensing mechanism installed in the electronic housing, which converts it into corresponding electrical pulses. By using the electronic circuitry to calculate the time difference between these two pulses, it is possible to accurately determine the displacement and liquid level being measured. Scope of application and features: This product is manufactured using imported chips and advanced manufacturing processes. It features a rational design, easy installation, a sophisticated structure, strong environmental adaptability, and requires no regular recalibration or maintenance. It features high precision, good stability, high reliability, a variety of output signals, a long service life, and safety and reliability. It is widely used for the monitoring, alerting, and control of physical parameters such as level, temperature, density, and interface conditions in fields including industrial process control, oil processing, pharmaceuticals, food processing, water treatment, and underground fuel storage at gas stations. Principle of operation of the pressure level transmitter: When a pressure sensor is inserted into or in contact with the liquid to be measured, the pressure P exerted by the medium is proportional to the height h of the liquid level, with a high degree of linearity. That is: P = ρgh, where ρ is the density of the medium being measured (kg/m3), g is the local acceleration due to gravity (m/s2), and h is the height of the liquid (m). For a given medium and at a fixed location, both ρ and g remain constant values. It is easy to obtain: h=P/(ρg). The expression above is the core formula in the working principle of level transmitters. A pressure proportional to the liquid level is detected by a transmitter probe (equipped with sensors) installed at the bottom of the container, and this pressure is converted into an electrical signal. This signal is transmitted to a conversion unit located on the liquid storage container, where it is transformed from a signal related to the liquid level into a standard 4–20mA signal, which is then output. Application scope: This product features reliable performance and excellent measurement accuracy. It is generally suitable for measuring the level of water-based media, crude oil, or other liquids. When measuring and controlling the liquid level using the immersion method, it is convenient to use a level transmitter with a standard output signal: it can be connected directly to digital control instruments and is interchangeable. An integrated level transmitter combines the level sensor and the signal transducer unit within the same water-sealed housing; its advantages are ease of use and good resistance to interference ； The downside is that the zero point cannot be adjusted, and drift at the zero point will be added to the overall accuracy. A split-type level transmitter involves placing the level sensor inside or into the liquid, while the transduction circuit unit is housed in another instrument enclosure – an instrument box or an explosion-proof housing for industrial transmitters. The two are connected to each other using a special cable equipped with a venting conduit. Its advantages are: both the zero point and sensitivity can be adjusted, and the installation method is flexible and convenient; it is particularly suitable for level control applications that require corrosion resistance, plug-in installation, resistance to media wear, resistance to clogging caused by various impurities in the medium, as well as applications where accuracy higher than 0.15% is required. Overview of Small Float Level Gauges (Level Switches) The small float level gauge (level switch) is a type of level switch that our company’s technical staff have developed specifically for customers, based on market demands and taking into account the company’s actual conditions. It also utilizes a magnetic field interacting with a sensor element (a reed switch) to generate a switch signal that reflects the liquid level. It can accurately output normally open and normally closed switch signals. The small floating ball level gauge (level switch) is a new product developed by our company based on improvements to the traditional floating ball level gauges (level switches). Compared to the company’s existing products, it features a small size, easy installation, rapid response, and high cost-performance ratio. Classification and main parameters: Based on the material of the main components such as the floating ball or guide rod, small floating ball level gauges (level switches) can be roughly divided into two series: metal floating ball series and plastic floating ball series. Metal float series: available in rod-type and cable-type versions.

The commonly used level gauges in water supply systems and the key points for their selection are as follows: a. Float-type level gauge A hollow float is placed in the liquid; when the liquid level changes, the float moves by an amount corresponding to that change in level. The displacement of the floating ball can be measured mechanically or electrically, with an accuracy of ±(1~2)%. This type of level gauge is not suitable for liquids with high viscosity, and its output can be controlled via a switch or provided as a continuous signal. 　　In the design of water treatment plants, this type of level gauge is often used to measure the level in the collection tank in order to control the automatic start and stop of the drainage pumps. b. Static pressure (or differential pressure) level gauge Since the static pressure of the liquid column is proportional to the liquid level, the liquid level can be determined by measuring the static pressure of the liquid column at the reference level using a pressure gauge. The pressure or pressure difference range is calculated based on the density of the medium being measured and the liquid measurement range; thereafter, a pressure gauge or differential pressure gauge with appropriate specifications such as range and accuracy is selected. The accuracy of this level gauge is ±(0.5~2)%. c. Capacitive level gauge: Electrodes are inserted into the container; as the liquid level changes, the medium inside the electrodes changes, and consequently the capacitance between the electrodes (or between the electrodes and the container walls) also changes. This change in capacitance is then converted into a standardized direct current signal. Its accuracy is ±(0.5~1.5)%. 　　Capacitive level gauges have the following advantages: the sensor has no mechanical moving parts, resulting in a simple and reliable structure ； High precision ； The detection end consumes little electrical power and has a fast dynamic response ； Easy to maintain and long-lasting. The disadvantage is that instability in the dielectric constant of the liquid being tested can cause errors. Capacitive level gauges are generally used for measuring the level in tanks such as treatment tanks and clear water tanks. 　　When the measurement range does not exceed 2m, rod-shaped, plate-shaped, and coaxial electrodes are used ； When it exceeds 2m, cable electrodes are used. When the medium under test is water, electrodes with an insulating layer (polyethylene can be used) are employed. d. Ultrasonic level gauge The sensor of an ultrasonic level gauge consists of a pair of transmitting and receiving transducers. The transmitting transducer emits ultrasonic pulses toward the liquid surface; these pulses are reflected back from the surface and captured by the receiving transducer. The distance between the sensor and the liquid surface can be determined based on the time taken for the signal to travel from transmission to reception, which can then be converted into the liquid level. Its accuracy is ±0.5%. 　　This type of level gauge has no mechanical moving parts, offering high reliability; it is simple and easy to install. It belongs to the category of non-contact measurement, and it is not affected by the liquid