[Dry goods] Si Ke liquid level measurement solution

The level includes liquid level and material level, and the liquid level measurement includes two parts: liquid level annunciator and continuous liquid level measurement. The liquid level signal measurement is to measure the liquid level of several fixed positions, for the upper and lower limit alarm of the liquid level, etc.; the continuous liquid level measurement is the linear output measurement of the liquid level change.

Liquid level measurement is widely used in many fields such as petroleum, chemical industry and food processing, and it has very important significance. In the liquid level measurement, there are many methods, but each has its own characteristics and application range:

1, contact level measurement

Contact measurement is a measurement method that starts from the steel belt float level gauge and gradually evolves to form a variety of different mechanical and electrical principles, such as guided wave radar, magnetostrictive, servo, tuning fork and photoelectric.

Steel belt float

In the earliest level gauge, the float floated on the surface of the medium by buoyancy, and the level value was read by the shift gear to the scaled steel strip. When the liquid level rises or falls, the force balance is broken, and the float also follows the rise and fall, driving the steel. Belt running. The installation is complicated and the reliability is low. Due to the large number of mechanical parts, it is easy to happen that the steel strip is stuck, and nowadays it is facing a new generation.

Guided wave radar level gauge

A liquid level measuring instrument commonly used in the industry is based on the principle of time domain reflection (TDR). The electromagnetic pulse of the radar level gauge propagates along the wire rope or probe at the speed of light. When encountering the surface of the measured medium, the radar gauge portion formed pulses are reflected back along the same path and the echo pulse transmitting means, transmitting means and the distance measured at the surface of the medium is proportional with the propagation time between pulses, the calculated liquid level.

Magnetostrictive

The upper end of the probe pulse voltage current generated from electronic components, start time, a magnetic field along the magnetostrictive wire travels down, the float with the level changes along the measuring rod moves up and down, the float magnets, also generates a magnetic field two meet, forming magnetostrictive wire twisting torsional stress wave pulse, the pulse rate is known, to calculate the pulse propagation time, i.e. corresponding to the level variation accurately.

Magnetostrictive level higher accuracy, the oil-water interface can be measured but the measurement of the contact and higher installation and maintenance is not required resulting in a wide market penetration.

Hydrostatic level gauge

The static pressure level gauge is special in that it uses the relationship between the pressure of the uniform liquid and the height to calculate the liquid level by measuring the pressure at the bottom of the liquid. P = ρgh (P pressure) is often less accurate due to its large density and temperature, and many other test instruments are needed to eliminate these effects.

It is mainly used in the industrial field, and the signal is led out by cables, mainly for some deep water measurement systems, such as hydropower stations, river dams, port deep water measurements, etc.

Servo level gauge

The basic principle is the same as the steel belt type liquid level gauge, but with the precise force sensor and servo system, forming a closed-loop adjustment system. By considering the gravity of the steel strip itself, the float height can be accurately adjusted to achieve balanced buoyancy and gravity, and the accurate current liquid level can be obtained. Go to the top of the tank to get the liquid level value.

Used in calm, lightweight, non-corrosive liquids. Installation and commissioning are cumbersome, and various disadvantages of the contact level gauge are also expensive.

Tuning fork level switch

A liquid point liquid level switch tool designed by the principle of a tuning fork, whose switching principle works by causing vibration of the piezoelectric crystal to cause vibration thereof. When subjected to material damping, the amplitude drops sharply and the frequency and phase change significantly. These changes are detected by the internal electronic circuit and, after processing, converted into a switching signal output. The product can monitor, control and alarm the high and low levels of the tank, suitable for a variety of liquid, powder, granular solids. It is practical, simple, reliable, and adaptable. It is basically maintenance-free.

Photoelectric level switch

The photoelectric level switch uses infrared detection, which uses the principle of light refraction and reflection, and the light will reflect or refract at the interface of two different media. When the measured liquid is in the high position, the measured liquid forms an interface with the photoelectric switch . When the measured liquid is in the low position, the air and the photoelectric switch form another interface, and the two interfaces make the photoelectric switch internal light The intensity of the reflected light received by the receiving crystal is different, that is, corresponding to two different switching states.

2, non-contact liquid level measurement

Non-contact measurement usually uses the form of the emission energy reflected by the measured medium. Using the known wave propagation speed, the distance between the liquid surface and the measuring instrument is obtained by directly or indirectly measuring the wave propagation time. Level value. There are ultrasonic level gauges and electromagnetic wave radar level gauges depending on the type of launch wave.

Ultrasonic level gauge

The ultrasonic level gauge is a digital level gauge controlled by a microprocessor.

In the measurement, the ultrasonic pulse is emitted by the sensor (transducer), and the sound wave is reflected by the liquid surface and then received by the same sensor or ultrasonic receiver, converted into an electrical signal by the piezoelectric crystal or magnetostrictive device, and transmitted and received by the sound wave. The time between the time to calculate the distance from the sensor to the surface of the liquid being measured. Due to the non-contact measurement, the measured medium is almost unlimited and can be widely used for the measurement of various liquid and solid materials.