Six Level Measuring Instruments and Relative Merits?

1. Float Level Meter

Figure 1: Different float level meters.

Float level meter is an instrument of measuring liquid level based on buoyancy principle. Usually, the combination of floating ball and scale enables the observer to intuitively read the height of liquid level.

Advantages: It can be read quickly and intuitively; Low price; Easy installation.
Disadvantages: Low precision; The installation shape of the container is relatively large; Not suitable for corrosive and dangerous media; Remote transmission and adjustment cannot be realized.

2. Magnetic Level Indicator

Figure 2: Magnetic level indicators.

Magnetic level indicator is an instrument for signal conversion and liquid level display by driving the magnetic flap outside the container to flip by the magnetic float installed inside the container.

Advantages: It can be read quickly and intuitively; Lower price; Remote transmission and adjustment can be realized.
Disadvantages: Low precision; Complex installation; Range limit; The installation volume is relatively large.

3. Capacitive Liquid Level Sensor

Figure 3: A Capacitive liquid level sensor.

Capacitive liquid level sensor measures the level of liquid level by using the change of capacitance between two plates of capacitance.

Advantages: Small size; Easy to realize remote transmission and adjustment; Suitable for corrosive and high pressure media.
Disadvantages: The dielectric constant of the medium and the upper part of the liquid level must be kept constant in order to measure accurately; The measuring range is limited by the length of the metal bar; High requirements for container materials; The measured medium has conductivity.

4. Radar Level Meter

Figure 4: A radar level meter.

The radar level meter converts the liquid / object surface position by detecting the information after the microwave (electromagnetic wave with very short wavelength) emitted by itself which is reflected by the liquid level.

Advantages: It can measure the liquid level in the pressure vessel and ignore the influence of high temperature, high pressure, scaling and condensate; High precision; No direct contact with the medium; Strong corrosion resistance; It can be used in vacuum environment; Easy installation.
Disadvantages: High price; Affected by the geometric structure and material characteristics of the container; Vulnerable to electromagnetic interference.

5. Ultrasonic Level Transmitter

Figure 5: An ultrasonic level transmitter.

The ultrasonic level transmitter is used to measure the liquid / object surface position by detecting the signal after the ultrasonic wave emitted by itself which is reflected by the liquid level.

Advantages: No direct contact with medium; Strong corrosion resistance; High precision; Easy installation.
Disadvantages: Expensive price; The ultrasonic wave is greatly affected by the gas composition of the transmission medium; It is greatly affected by the geometric characteristics of the container; Not applicable to media with bubbles or suspended solids; Vulnerable to electromagnetic interference.

6. Bubble Level gauge

Figure 6: A bubble level gauge.

The bubble level gauge inflates the medium from the bottom of the container through the air. Only when the blowing pressure in the air supply system is balanced with the hydrostatic pressure at the bottom of the container will the gas enter the container from the air pipe to form bubbles. At this time, measuring the air pressure in the air supply system can convert the static pressure of the measuring point, and then get the liquid level value.

Advantages: Strong corrosion resistance; Capable of measuring high temperature medium.
Disadvantages: High maintenance cost and Low accuracy.

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