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A mechanical water meter has a propeller, also called a paddle wheel. This could operate on the basis of two different principles:

• The Woltman-principle: in this case the propeller is perpendicular to the flow direction of the water. The meter has two magnetic bridging variants. As a result very few parts of the meter come in contact with the water, so there are hardly any problems with resistance or wear.

• The Multi-Jet principle: the propeller of this water meter is actuated to be used for multiple water jets. There is a magnetic bridging in the meter of the rotating propeller towards the dry counter. This counter has little toothed wheels that register how much water is running through the meter. Since more parts of the meter come into contact with the water using this principle, this type of water meter is more sensitive to wear and there are more problems with resistance.

A mechanical water meter can be executed with or without pulse. A water meter with pulse will give a pulse after every x-number of liters, for example after every 10 or 100 liters. A meter without pulse will not do this.

Electronic water meters have no moving parts. The most common electronic water meter is the ultrasonic water meter. This will measure the quantity of water by means of sound waves. This type of water meter has multiple advantages in comparison with mechanical water meters:

• The meter operates on the basis of sensors. As a result it can measure in two directions. 
• Since the meter has no moving parts, it is less subject to wear, resulting in a longer lifespan. 
• The meter has no paddlewheel or propeller, so there is no resistance. As a result, the meter is less likely to become polluted. This makes this type of water meter also suitable for drain water, which is often (strongly) polluted. 

Still an ultrasonic water meter also has a disadvantage; this type meter is sensitive to air in the piping. Sound waves will behave differently air than they do in water. As soon as there is air in the piping, the meter will stop and due to the flow alarm also the irrigation will stop. Specifically systems that operate by means of water suction or have an open outflow into a ditch or silo, will often have air in the piping. In that case you had better choose a mechanical water meter. This will not stop when there is air in the piping; it will merely show an erroneous measurement value.  

A water meter has a certain capacity. The required capacity depends on the quantity of water that runs through the water meter. Always ask proper advice regarding this. 

Source: Revaho

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