How to choose between ultrasonic flowmeter and electromagnetic flowmeter?

As the two most important forms of flow meter in the current flow measurement field, how to choose? Xiaobian elaborates on the characteristics of the following two from the following aspects, hoping to provide some suggestions on selection.

1. Ultrasonic flowmeter

How to choose between ultrasonic flowmeter and electromagnetic flowmeter?

Measuring principle of ultrasonic flow meter:

At present, there are two main measurement principles of ultrasonic flowmeters used in the industry, one is the time difference method, and the other is the Doppler principle, which is dominated by the time difference method.

Time difference measurement principle: when ultrasonic waves propagate along the flow and counterflow in the fluid, the propagation speed of the two is different, the downstream flow is fast, the reverse flow is slow, the time difference between the two is proportional to the flow rate of the fluid itself, and the flow rate is measured by measuring and calculating the time difference, and then the flow rate is measured.

Selection characteristics of ultrasonic flowmeter:

Advantage:

It has a wide range of applications, and all kinds of homogeneous liquids, gases, and vapors can be measured.

Ideal for use in fluids with high sanitary requirements or strong acids and alkalis.

Installation is extremely easy, as the clamp-on type simply binds the sensor to the outer wall of the pipe.

Non-contact measurement, no barrier elements, independent of operating pressure (except gases),

The measuring range is extremely wide, and the maximum measurement ± is 32m/s, and the measurement effect of low flow rate is good.

Virtually maintenance-free.

Inferior position:

There are certain requirements for straight pipe sections, generally requiring five times the pipe diameter of the first ten and five times the last.

When installing, you need to set the necessary parameters,

Poor measurement results are performed on fluids with a large number of particles or large amounts of air bubbles.

2. Electromagnetic wave flowmeter

Electromagnetic flowmeter measuring principle:

The structure of an electromagnetic flowmeter is mainly composed of a magnetic circuit system, a measuring catheter, an electrode, a housing, a lining and a converter. When the conductive fluid flows through the pipeline with an external magnetic field, an induced electromotive force is generated under the action of the magnetic field, and the induced electromotive force is proportional to the fluid flow velocity, and the flow rate is measured by measuring the induced electromotive force. Faraday's law of induction states that a conductive liquid flowing within a magnetic field produces an electromotive force (voltage) that is proportional to the inner diameter of the pipe, the strength of the magnetic field, and the average flow velocity. E is proportional to V × B × A.

Selection characteristics of electromagnetic flowmeter:

Advantage:

The scope of application is very wide, the technology is mature, and the operation is stable.

Wide range of measuring ranges.

・Measurement is not affected by the temperature, pressure, density, or viscosity of the liquid

・Capable of detecting liquids containing contaminants (solids, bubbles).

・No pressure loss

・No moving parts (improved reliability)

It can measure fluids such as acids and bases, high turbidity, or slurries

Inferior position:

Fluids with low conductivity, such as ultrapure water, demineralized water, and distilled water, cannot be measured.

Cannot measure gases or vapors,

The diameter is large, the cost and installation are complex, and the maintenance cost is high.

How to choose between ultrasonic flowmeter and electromagnetic flowmeter?

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