Five common liquid level sensors

In daily life, the common liquid level sensors mainly include capacitive liquid level sensors, floating ball liquid level sensors, ultrasonic liquid level sensors, radar liquid level sensors and submersible liquid level sensors.

Due to their different design principles and measurement methods, the measurement range and applicable scenarios are also different. And how are their design principles and measurement methods specifically designed? The following is the introduction of Raya Technology for you.

01-Capacitive Liquid Level Sensor

The capacitive liquid level sensor uses the capacitive detection principle, and the capacitive liquid level gauge measures the level of the liquid level by measuring the change of capacitance.

It is a metal rod inserted into the liquid container, the metal rod is used as one pole of the capacitor, and the container wall is used as the other pole of the capacitor. The medium between the two electrodes is the liquid and the gas above it.

Since the dielectric constant ε1 of the liquid and the dielectric constant ε2 on the liquid surface are different, for example: ε1>ε2, when the liquid level rises, the total dielectric constant value between the two electrodes of the capacitive liquid level gauge increases accordingly. Therefore, the capacitance increases.

Conversely, when the liquid level drops, the value of ε decreases, and the capacitance also decreases.

02-Float-type liquid level sensor

The float type liquid level sensor uses the magnetic float of the float level switch to rise or fall with the liquid level, so that the reed switch chip at the set position in the sensor detection tube acts, and sends out the contact opening (closing) conversion signal.

One or more reed switches are installed in a closed non-magnetically conductive tube, and then the tube is passed through one or more floating balls with a ring magnet inside. The rise or fall of the liquid will drive the floating balls to move up and down together. Thereby, the reed switch in the non-magnetically conductive tube can be pulled in or disconnected, thereby outputting a switch signal.

The float level sensor has a wide range of applications and is economical and practical. It is often used in monitoring fields such as sump pits, fire pools, and sewage treatment. It is not suitable for monitoring in the food hygiene industry. In addition, it can also be used in diverse scenarios such as scientific research and lake biodiversity detection, and the future application potential is optimistic by many parties.

03-Ultrasonic Liquid Level Sensor

Ultrasonic liquid level sensor is a non-contact sensor that uses the principle of ultrasonic reflection, that is, the liquid level height is calculated by monitoring the time difference between ultrasonic transmission and reflection, so as to achieve the purpose of liquid level measurement.

It has the characteristics of non-contact, simple installation and high flexibility, but the installation environment requires that there should be no obstacles to block the signal at the position below the monitoring. Ultrasound has a great penetration ability to liquids and can penetrate to a depth of tens of meters or even higher. It can be used in application scenarios such as hydrological monitoring, sewage monitoring, and tank liquid level monitoring.

04-Radar Liquid Level Sensor

The radar liquid level sensor has the same advantages as the laser measurement principle, and is not affected by the measurement medium, and is less affected by the external environment, and does not require repeated calibration, but the measurement height is generally within 6 meters, especially suitable for heating steam. In-tank measurement of large containers, such as residual oil, asphalt and other monitoring fields.

05-Hydrostatic Liquid Level Sensor

The measurement principle is that the static pressure generated by the liquid column is a function of the liquid density and liquid level. The pressure sensor installed at the bottom of the storage tank measures the gauge pressure relative to the atmospheric pressure, and converts the measured value into liquid level according to the known medium density.

The principle is p=ρgh, where p is the pressure, ρ is the liquid density, g is the gravitational acceleration constant, and h is the liquid level height.

When the gas pressure (atmospheric pressure), liquid density and gravitational acceleration are constant, the liquid pressure in the tank is proportional to the liquid level in the tank. The principle of the static pressure liquid level sensor is simple, and it is generally installed on the side wall or bottom of the tank. Hydrostatic level measurement is suitable for almost all media, and in the absence of pressure or temperature fluctuations, storage tanks can be monitored with hydrostatic level gauges, such as raw water tanks or demineralized water tanks.

When the tank volume of the pharmaceutical water storage system is small, the water temperature fluctuates frequently or the tank works under pressure, the hydrostatic level gauge is prone to liquid level drift, so it is less used in the storage system of pharmaceutical water such as water for injection and purified water. middle.

Rika Sensor

RIKA professional liquid level monitoring solution

For various industries that have liquid level monitoring needs, Ruiyi Card has its own set of professional liquid level monitoring solutions, which can monitor the liquid level of various liquids such as purified water, sewage, lubricating oil, diesel oil, and hydraulic oil.

RIKA liquid level monitoring sensors are designed in two types: contact type and non-contact type according to customer requirements and working conditions selection requirements. The products are divided into input liquid level, capacitive liquid level, ultrasonic liquid level, radar liquid level and other sensor series .

Products are widely used in oil level monitoring in lakes, rivers, reservoirs, oceans, sewage treatment, sump, fire pool, construction machinery, chemical industry and other fields.

RKL-01 Submersible Level Transmitter

RKL-01 submersible liquid level transmitter adopts stainless steel isolation diaphragm and diffused silicon pressure core. The pressure core adopts laser trimming resistance technology, which can perform temperature compensation for zero point and sensitivity in a wide temperature range.

At the same time, it uses a special cable and waterproof technology with an atmospheric conduit to ensure water tightness, and with an atmospheric conduit, it is beneficial to obtain accurate and stable measurement data.

RKL-02 Radar Level Gauge

The RKL-02 radar level gauge (with display) antenna emits a very narrow microwave pulse, which is transmitted in the air at the speed of light, and when it encounters the surface of the measured medium, part of its energy is reflected back and received by the same antenna.

The time interval between the transmitted pulse and the received pulse is proportional to the distance from the antenna to the surface of the measured medium, which can be used to calculate the distance from the antenna to the surface of the measured medium.

RKL-03 Ultrasonic level gauge (with display)

RKL-03 ultrasonic level gauge (with display) is a non-contact, highly reliable, cost-effective, easy-to-install and maintain level measuring instrument. It can meet most level measurement requirements without contacting the measuring medium.

The time interval between the sensor transmitting and receiving pulses is proportional to the distance from the antenna to the surface of the measured medium, which can be used to calculate the distance from the antenna to the surface of the measured medium. This product can be used with RK600 series data recorders or general collectors.

RKL-04 Capacitive Liquid Level Sensor

RKL-04 capacitive liquid level sensor uses coaxial capacitance as the sensing part. When the liquid enters the capacitor, it will cause the capacitance change between the sensor shell and the sensing electrode. This change is passed through the subsequent acquisition and conversion circuit and precise linearity and temperature Compensation, output standard voltage, current and digital signal required on site (sampling frequency is adjustable).

RKL-04 is made of food-grade Teflon and 304 stainless steel material, fully welded structure, high hygiene level, high breaking strength; long-term work stability and high reliability. Used to measure: oil (gasoline, diesel, hydraulic oil, lubricating oil), water (sewage), beverage, medical, chemical and other liquid media, suitable for high and low temperature occasions. It has a very wide measuring range: 0.03...6m, especially suitable for measuring the height of liquids below 500mm.

Conclusion

With the development of science and technology today, human beings have invented countless liquid level measurement methods, from ancient rulers to modern capacitive, photoelectric, ultrasonic, and radar measuring instruments.

Nowadays, liquid level sensors and liquid level switches have become "top players" in petrochemical, metallurgy, electric power, pharmaceutical, water supply and drainage, environmental protection, home appliances and other fields, and play an important role in our lives. 

In addition, under the rapid development of the Internet of Things in recent years, the submersible liquid level sensor has a unique advantage in the liquid level sensor market with the advantages of accurate measurement, high precision, fast response, advanced technology and low power consumption, and can adapt to With the development of the Internet of Things society, the sturdy stainless steel package makes it easy to measure the liquid level of most media, and occupies a leading position in the contact liquid level measurement.