4-20MA/0-10V Liquid Level Sensor

You also ask

What is a liquid-level sensor?

A liquid level sensor (static pressure level gauge/level transmitter/level sensor/water level sensor) is a pressure sensor that measures liquid level. The static pressure input type liquid level transmitter (level gauge) is based on the principle that the measured liquid static pressure is proportional to the height of the liquid. It adopts foreign advanced isolated diffused silicon-sensitive elements or ceramic capacitor pressure-sensitive sensors, The voltage is converted into an electric signal, and then after temperature compensation and linear correction, it is converted into a standard electric signal (usually 4～20mA/1～5VDC)

What are the different types of level sensors?

Level transmitters are divided into two categories:

The first type is contact type, including single-flange static pressure/double-flange differential pressure level transmitter, float type level transmitter, magnetic level transmitter, drop-in level transmitter, electric internal Float level transmitter, electric float level transmitter, capacitive level transmitter, magnetostrictive level transmitter, servo level transmitter, etc.

The second category is the non-contact type, which is divided into ultrasonic-level transmitters, radar-level transmitters, and so on.

The hydrostatic input level transmitter (level gauge) is suitable for level measurement of various media in petrochemical, metallurgical, electric power, pharmaceutical, water supply and drainage, environmental protection, and other systems and industries. The exquisite structure, simple adjustment, and flexible installation provide convenience for users to use easily. Standard signal output modes such as 4-20mA, 0-5v, and 0-10mA can be selected by the user according to their needs. Using the principle of hydrostatics to measure liquid levels is an important application of pressure sensors. The use of a special cable with a ventilation duct in the middle and a special sealing technology not only ensures the water tightness of the sensor but also makes the reference pressure chamber communicate with the ambient pressure, thereby ensuring the high accuracy and stability of the measurement.

How does a liquid-level sensor work?

The working principle of different types of liquid-level sensors is different.

1. Float-type liquid level sensor

The buoy-type liquid level transmitter changes the magnetic float to a buoy, and the liquid level sensor is designed according to Archimedes' buoyancy principle. The float-type liquid level transmitter uses the tiny metal film strain sensing technology to measure the liquid level, boundary level, or density of the liquid. It can be used for routine setting operations through the on-site buttons when it is working.

2. Floating ball type liquid level sensor

liquid level sensor

Liquid level sensor (5 photos)

The float-type liquid-level transmitter consists of a magnetic float, a measuring tube, a signal unit, an electronic unit, a junction box, and installation parts. Generally, the specific gravity of the magnetic float is less than 0.5, which can float above the liquid surface and up and down along the measuring tube Moving, the catheter is equipped with a measuring element, which can convert the measured liquid level signal into a resistance signal proportional to the change of the liquid level under the action of external magnetism, and convert the electronic unit into 4-20mA or other standard signal output.

The liquid level sensor is a modular circuit, which has the advantages of acid resistance, moisture resistance, shock resistance, corrosion resistance, etc. The circuit contains a constant current feedback circuit and an internal protection circuit, which can make the maximum output current not exceed 28mA, so it can reliably protect the power supply and make the secondary meter not damaged.

3. Hydrostatic liquid level sensor

The transmitter uses the measuring principle of hydrostatic pressure to work. It generally uses a silicon pressure sensor to convert the measured pressure into an electrical signal, which is amplified by an amplifier circuit and compensated by a compensation circuit, and finally 4-20mA or 0-10mA Current mode output.

How do you check liquid levels?

When the liquid level transmitter is thrown into a certain depth in the measured liquid, the formula for the pressure on the liquid surface of the sensor is Ρ = ρ .g.H + Po where:

P: pressure on the face of the transmitter

ρ: Density of the measured liquid

g: local acceleration of gravity

Po: atmospheric pressure on the liquid surface

H: the depth of the transmitter into the liquid

At the same time, the pressure of the liquid is introduced into the positive pressure cavity of the sensor through the gas-conducting stainless steel, and then the atmospheric pressure Po on the liquid surface is connected to the negative pressure cavity of the sensor to offset the Po on the back of the sensor.

Make the pressure measured by the sensor: ρ .g.H, obviously, by measuring the pressure P, the liquid level depth can be obtained.