Description: The bubbler is a common method of water level measurement, equipped with a non-submersible pressure transducer. The bubbler typically consists of a compressor, orifice line, pressure transducer, tank and desiccant. Also known as a gas-purge system, the bubbler allows a small quantity of air or inert gas (e.g. nitrogen) to bleed through a pipe or tubing to an orifice in the stream. Early versions of this system used nitrogen supplied from a tank that had to be regularly replaced. The pressure of the air that displaces the liquid in the orifice is then measured by a pressure transducer. There are two types of bubblers on the market
Costs USD Lower: $4,000
Costs USD Upper: $6,000
Accessories: HL-C01
Advantages: a continuous and non- continuous bubbler. A continuous bubbler keeps the orifice line under pressure by producing approximately 1 bubble per second. Bubble rates are generally increased as orifice lines get longer. Orifice lines of 100 m or more have been installed at some sites. The non- continuous bubbler only turns on at a set time allowing water to feed back up the orifice line, requiring the sensor to purge and stabilize the line. The argument between non-continuous vs continuous bubbler systems goes on today, which is usually argued by manufacturers trying to sell one solution over the other.
Bubblers can be specified to the range of maximum head of water, usually between 0 to 50m. With reservoir systems with a wide range of elevation (>20m) the concept of a manifold system utilizing several orifice lines covering 20m ranges. Each orifice line can be staggered at a single location. This example would be orifice lines of 0-20m, 15-35m, 30-50m. The operator would use the orifice line that best matches the measurement requirements. The manifold system allows for the use of a lower range to have higher precision. Ideal locations for the bubbler include open channels and reservoirs. The location should have a stable river bed channel free from debris and shifting bedloads that can damage or block the orifice line."
Disadvantages: Bubblers are well suited in reservoirs with shallow slopes where non-contact sensors are unable to measure the full range of water level. The orifice line (the least expensive component) is the only component under water. The most expensive components are not located in the water. In the event the orifice pipe is damaged by debris carried in high water (trees, boulders, other), the orifice pipe and orifice tube can be replaced at relatively low cost.
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