Types and principles of liquid level gauges

1. Magnetic flap liquid level gauge
Magnetic plate level gauge: also called magnetic float level gauge, magnetic flip column level gauge.
Principle: Connector principle, developed based on the buoyancy principle and magnetic coupling. When the liquid level in the container under test rises and falls, the magnetic steel in the float is transmitted to the magnetic flip column indication panel through magnetic coupling, causing the red and white flip column to flip. 180°, when the liquid level rises, the flip column turns from white to red, and when the liquid level drops, the flip column turns from red to white. The junction of red and white on the panel is the actual height of the liquid level in the container, thereby realizing liquid level display.

2. Float level gauge
Principle: The structure of the float level gauge is mainly designed and produced based on the principles of buoyancy and static magnetic field. The position of the float with a magnet (referred to as the float) in the measured medium is affected by buoyancy: changes in the liquid level cause changes in the position of the magnetic float. The magnets and sensors (reed switches) in the float ball change the number of components (such as fixed-value resistors) connected in series to the circuit, which in turn changes the electrical quantities of the instrument circuit system. That is to say, changes in the position of the magnetic float cause changes in electrical quantities. The liquid level in the container is reflected by detecting changes in the electrical quantity of the liquid level gauge.

3. Steel strip liquid level gauge
Principle: It is designed and produced using the principle of mechanical balance. When the liquid level changes, the original mechanical balance will reach a new balance through the movement of the steel strip when the float is disturbed by the buoyancy force. The liquid level detection device (float) drives the steel belt to move according to the liquid level. The displacement transmission system drives the transmission pin to rotate through the movement of the steel belt, and then acts on the counter to display the liquid level.

4. Radar level gauge
Principle: Radar level gauge is a measuring instrument based on the time travel principle. Radar waves run at the speed of light, and the running time can be converted into level signals through electronic components. The probe emits a high-frequency pulse and propagates along the cable probe. When the pulse encounters the material surface, it is reflected back and is received by the receiver in the instrument, which converts the distance signal into a level signal.



5. Magnetostrictive level gauge
Principle: When the sensor of the magnetostrictive level gauge works, the circuit part of the sensor will excite a pulse current on the waveguide wire. When the current propagates along the waveguide wire, a pulse current magnetic field will be generated around the waveguide wire. There is a float outside the sensor rod of the magnetostrictive liquid level meter. This float can move up and down along the rod as the liquid level changes. There is a set of magnetic rings inside the float. When the pulsed current magnetic field meets the magnetic ring magnetic field generated by the float, the magnetic field around the float changes, causing the waveguide wire made of magnetostrictive material to generate a torsional wave pulse at the position of the float. This pulse moves along the direction of the float at a fixed speed. The waveguide wire is transmitted back and detected by the detection mechanism. By measuring the time difference between the pulse current and the torsional wave, the position of the float, that is, the position of the liquid level, can be accurately determined.

6. Radio frequency admittance level meter
Principle: The radio frequency admittance level meter consists of a sensor and a control instrument. The sensor can be installed on the top of the silo using a rod, coaxial or cable probe. The pulse card in the sensor can convert the change in material level into a pulse signal and send it to the control instrument. After calculation and processing, the control instrument converts it into an engineering quantity and displays it, thereby realizing continuous measurement of the material level.

7. Tuning fork level meter
Principle: The working principle of the tuning fork level controller is to make the tuning fork vibrate at a certain resonance frequency through a pair of piezoelectric crystals installed on the tuning fork base. When the tuning fork comes into contact with the medium being measured, the frequency and amplitude of the tuning fork will change. These changes are detected, processed and converted into a switching signal by the intelligent circuit.

8. Glass plate level gauge (glass tube level gauge)
Principle: The glass plate liquid level meter is connected to the container through a flange to form a connector. The liquid level in the container can be directly read through the glass plate.

9. Pressure level transmitter
Principle: The pressure type liquid level gauge adopts the principle of static pressure measurement. When the liquid level transmitter is put into a certain depth of the liquid to be measured, the pressure of the liquid is introduced into the sensor through the gas-conducting stainless steel while facing the pressure on the liquid surface. The positive pressure chamber of the sensor is connected to the atmospheric pressure Po on the liquid surface and the negative pressure chamber of the sensor to offset the Po on the back of the sensor, so that the pressure measured by the sensor is: ρ.g.H. By measuring the pressure P, the liquid level can be obtained depth.

10. Capacitive liquid level meter
Principle: Capacitive liquid level gauge measures the level of liquid level by measuring changes in capacitance. It is a metal rod inserted into a liquid container. The metal rod serves as one pole of the capacitor and the container wall serves 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 is different from the dielectric constant ε2 on the liquid surface, for example: ε1>ε2, when the liquid level rises