Pros and cons of the types of liquid level indicators
Author:vacorda Source:vacorda.com Date: 2017-01-18 15:23:23
There are many types of level instruments in the industry field, usually there are magnetic level indicators, float ball level indicators, capacitance level indicators, radar level indicator, ultrasonic level indicator, etc. Although there are different appearance and principle of these types of level instruments, there are all level indicators for liquid level measurement, and what’s the most important is that how to choose the most suitable instruments for actual working conditions. Here we list some pros & cons of the most used level instruments. Hope it will be available.
(Display of typs of level gauge instruments)
Glass tube level indicator
Principle: Glass tube level indicator, an ordinary connected type level indicator.
Features: simple structure, cheap, intuitive, suitable for on-site use, but easily damaged, easy to contaminate the dirt on the inner surface, resulting in reading difficulties, and not easy to remote transmission and regulation.
Improvement: If the level gauge used in outdoor, the heating tube can be added, for obvious display, optional two-color form. If the medium is corrosive medium acid, glass tube can be replaced into F46 tube, both ends of the valve can be replaced with PP or F4.
Float ball level indicators
Principle: Float ball level indicators, put a hollow float into the liquid, when the liquid level changes, the float will produce the same displacement with the change of the liquid level, though the magnetic components in the middle of the float, can measure the position change of the float by the mechanical or electrical method.
Features: Accuracy of ± (1 ~ 2)%, the output end with the switch control and continuous output. It is simple in structure, low price, generally not suitable for high viscosity liquid. Float level gauge for measuring the liquid level in industrial and civil water tower, pool, water tanks, sumps and industrial tanks, widely used in the departments of liquid level, chemical, metallurgy, power, paper, food and Industrial sewage treatment.
Improved methods: for high viscosity liquid, it can be measured by using the large float of top-mounted and side mounted electric.
Ultrasonic level indicators
Principle: The ultrasonic level indicator use of ultrasound in the gas, liquid attenuation, penetrating power and acoustic impedance to measure the nature of the interface between two media.
Features: Accuracy is ± 0.5%. this instruments have high precision, fast response, no mechanical moving parts, high reliability, simple installation, belongs to non-contact measurement, and is not affected by the liquid viscosity, density, but it is high cost and difficult in maintenance and repair. The instrument uses DC or AC power supply, with 4 ~ 20mA DC, high and low switch output.
Disadvantages: atmospheric use, the temperature below 100℃, because the usage temperature is low for most of the transducer. In addition it will affect the measurement accuracy if there is dust and steam mixed in medium.
Magnetic level indicator
Principle: the magnetic flp level gauge includes two part: the magnetic indicator and the float. The magnetic indicator consists of a red-and-white magnetic pole with a small magnetic steel or magnetic flop and guard plate. And the working principle of level measuring is the use of the principle of buoyancy and magnetic coupling. For detailed working principle of magnetic level gauge, please visit our previous article on Aug. 22nd, 2016.
Features: In addition to on-site instructions, it can also equip the remote transmitter, alarm switch, control switch, etc. Direct intuitive readings, eye-catching. The body of the indicator and the measured medium is completely isolated, thus good sealing, and high reliability, use safety. Simple structure, easy installation, low maintenance costs. Corrosion-resistant, no power, explosion-proof. According to the installation location in the container, it provides two forms: side loading and top loading.
（Installation ways of magnetic level gauge）
Radar level indicator
The basic principle: the radar level indicator emits low and short microwave energy pulses, it’s launch and reception through the antenna system, radar waves run at the speed of light, and the tuning time can be converted into level signal by electronic components, and the use of special time extension method can ensure making a stable and accurate level measurement in a very short period of time. Applied to the non-contact continuous level measurements for liquid, slurry and granular material, suitable for the occasions of large changes of temperature and pressure, and where the presence of inert gas volatilization.
Features: with high precision, high reliability, easy to use, but the price is slightly higher than the ultrasonic level meter. The instrument uses the microwave pulse measurement method, can work normally in the industrial frequency band range, beam energy is low, and it can be installed in a variety of metal, non-metallic containers or pipes, and it is not hurt the human body and the environment.
Disadvantages: high prices, and it affected by the dielectric constant of the medium. Dust and steam also affect the measurement. A greater impact on RF interference.