What is A Level Transmitter?

Figure 1: A level transmitter.

1. Definition

Level transmitter is the extension and development of pressure transmitter technology. It realizes the accurate measurement and transmission of the volume, liquid height and weight of water, oil and paste according to the principle that the pressure generated by liquids with different specific gravity at different heights is linear. And it can be widely used in metallurgy, mining, petrochemical industry, shipbuilding industry, locomotive manufacturing and other industries.

2. Working Principle

The working principle of the level transmitter is that when the two pressures of the measured medium are connected to two chambers(low pressure chamber and high pressure chamber), the pressure will act on the isolation diaphragm on both sides of the δ element (sensitive element) and be transmitted to both sides of the measuring diaphragm through the isolation diaphragm and the filling liquid in the element.

3. Advantages

It has simple installation, convenient use and strong interchangeability.
It has high sensitivity and fast response. And it can accurately reflects the subtle changes of flowing or static liquid level.
It has the ability of intrinsically safe explosion-proof and isolation explosion-proof, and can be used in various dangerous places.
It has anti blocking design which can measure the liquid level of paste medium.
It is suitable for the measurement of liquid level and interface of liquid medium in container. In addition to field indication, it can also be equipped with remote transmitter and alarm switch.
The indication is novel, the reading is intuitive and eye-catching, and the direction of observing the indicator can be changed according to the needs of users.
The measuring range is large and is not limited by the height of the storage tank.
The indicating mechanism is completely isolated from the measured medium with good tightness, high reliability and safe use.

4. Classification

4.1 Single Flange Level Transmitter

Figure 2: A single flange liquid level transmitter.

Single flange liquid level transmitter includes flat flange and flange liquid level transmitter with insertion barrel. Both of them measure the height of liquid level by using the self gravity of the measured medium. Single flange liquid level transmitter is suitable for medium with high viscosity and easy crystallization. It is generally used for the installation of open containers or equipment.

4.2 Double Flange Liquid Level Transmitter

Figure 3: A double flange liquid level transmitter.

Double flange liquid level transmitter is a differential pressure transmitter which provides a reliable measurement method to prevent the measured medium from directly contacting the isolation diaphragm of the transmitter. The main feature is the need to isolate the high-temperature medium from the transmitter. The measuring medium has corrosive effect on the sensitive components of the transmitter. And the sensor probe needs to be strictly purified to replace the measured medium. Double flange liquid level transmitter is mainly used to measure the liquid level of sealed pressure vessels.

4.3 Input Level Transmitter

Figure 4: An input level transmitter.

The input level transmitter has rod type and pull type. The principle is based on the fact that the measured hydrostatic pressure is directly proportional to the height of the liquid. It uses the piezoresistive effect of diffused silicon or ceramic sensor to convert static pressure into electrical signal. Then it is converted into 4-20madc standard current signal output through temperature compensation and linear correction. Because the transmitter has the characteristics of convenient installation, simplicity and strong adaptability, it can carry out high-precision measurement from water, oil to paste with high viscosity which is not affected by the foaming and deposition of the measured medium.So, it is generally used for the installation of open containers or equipment.

4.4 RF Capacitance Liquid Level Transmitter

Figure 5: A RF Capacitance Liquid Level Transmitter.

The principle of RF capacitance liquid level transmitter is that when the probe stage and conductive liquid form a capacitor, the metal inner core of the probe stage line is used as one pole of the capacitor, the conductive liquid is used as the other pole of the capacitor, and the middle is high stability polytetrafluoroethylene. The insulating outer layer of the probe wire is used as the medium between the two poles. With the change of liquid level, the area of the liquid surrounding the probe line changes, so that the relative area of the two poles of the capacitor changes. When the liquid level rises, the capacitance will increase, and the RF circuit converts this change into analog signal output. For RF capacitance liquid level transmitter, measuring high temperature and pressure is as simple as measuring normal temperature and pressure. And the measured value is not affected by the temperature and specific gravity of the measured liquid and the shape and pressure of the container. It is mainly used for liquid level measurement of acid-base, chloride, organic solvent, liquid CO2, ammonia, PVC powder, ash, oil-water interface, traditional Chinese medicine and so on.the container. It is mainly used for liquid level measurement of acid-base, chloride, organic solvent, liquid CO2, ammonia, PVC powder, ash, oil-water interface, traditional Chinese medicine and so on.

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