Flow meter is one of the major industrial measuring devices. The precision and range of the __sanitary flow meter__ must be higher and higher with the advancement of industrial manufacturing and flow calculation technology is changed every day. Do you know how many types of flow meter has? To conform to different applications, different kinds of flowmeter have emerged one by one. More than 100 types of flowmeters have currently been used. Next, we are going to show you the classifications of flow meter.

**Classification by principle of flow meter measurement**

1. Mechanical theory. Differential pressure form and rotor type utilizing the Bernoulli theorem are the devices that apply to this type of principle; Form of impulses and moving tube dependent on momentum theorem; The direct mass formula of the second rule of Newton is used; Target type dependent on the theory of fluid momentum; use the theorem of angular momentum, the type of turbine; Vortex form and street type vortex dependent on the theory of fluid oscillation; Form of pitot tube, constructive type of displacement, weir and trough type, etc..

2. Electrical principles: electromagnetic form, differential capacitance type, inductant type, strain resistance type, etc. shall be found with this type of concept.

3. Acoustic principle: ultrasonic, acoustic and so on are used to calculate the flow.

4. Heat theory: heat form, direct calorimetry method, indirect calorimetry type and so on are used to calculate flux using heat principle.

5. Optical principle: laser form, photoelectric type, etc. are those devices.

6. Based on physical principle: magnetic nuclear resonance form, type of nuclear radiation, etc.

7. Other principles: theory of labeling (tracer concept, nuclear magnetic resonance principle), principle of correlation, etc.

__Classification according to the flow meter form theorem__

1. Positive flowmeter

The volumetric flowmeter is similar to a regular container volume that tests the flow medium continuously. The bigger the traffic, the more measuring times and the higher the processing frequency. The volumetric flow meter concept is basic and ideal for calculating the high viscosity and low Reynolds fluid. The latest products are divided in oval gear flowmeter, waist wheel flowmeter, rotary pistons flowmeter, and scraper flowmeter according to the various shapes of the turning bodyshell; servo volumetric flowmeter, diaphragm flowmeter and rotary flowmeter are ideal for gas flow measurement.

2. The flowmeter of the impeller

The operating theory of the rotor fluid meter is to place the rotor into the calculated fluid and rotate under the fluid flow effect. The speed of rotation of the impeller represents the flow rate. The standard flowmeter of the impeller is the water meter which turbine flowmeter, and may be a kind of mechanical performance or electrical pulse type in its configuration. The water meter with the mechanical transmission quality is generally poor and the error is approximately 0 ± 0. However, the structure is basic and the costs are minimal. It was manufactured in mass in China and standardized, widespread and serialized. The flowmeter with electric pulse signal performance is highly accurate, although the overall error is 0 ± 2 percent – 0.5 percent.

3. Differential flowmeter pressure (variable pressure drop flowmeter)

The pressure differential flow meter consists of main and secondary equipment. The main unit is named the flow meter. It is mounted in the fluid pipeline to calculate and provides a flow-proportional pressure differential (velocity) for the secondary system to view the flow. The secondary unit is named the monitor device. The differential pressure signal produced by the measuring unit is received and converted to the corresponding display flow. The main instrument of the differential pressure flowmeter is normally throttling or dynamic pressure measurement (Pitot tube, averaging tube, etc.). Secondary sensors are mechanical, computer and combined differential pressure meters and flow display tools of both sorts. Much of the differential pressure responsive components of differential pressure meters are elastic components. The flow display instruments are fitted with square root devices to linearize the flow scale due to the square root connection between differential pressures and the flow. Most instruments are often fitted with a flow totalizer to display cumulative flow for financial accounting. The differential pressure system is a lengthy and comparatively mature method for measuring flow. It is widely used on important occasions worldwide, representing approximately 70% of any kind of flow measurement process. This meter is used to monitor key vapor, feed water and condensate flow throughout the power plant.

4. Variable flowmeter field (constant flowmeter decrease pressure).

The float in the conical channel is guided by the fluid force that flows from the bottom to the tip. If this force is matched with the "indicated weight" of the float, the trap will rest if its weight is reduced to the buoyancy of the fluid. The float height at rest may be used as a flow rate indicator. Since the flowmeter region differs from float height and while the float is steady, the pressure differential of the upper to the lower sections is equivalent, the flowmeter is called variable area flowmeter. The rotameter is the standard instrument for this kind of flowmeter.