A gauge that feeds a slow stream of nitrogen or air down a tube to a fixed orifice below the water. The pressure needed to keep gas bubbling out equals the water pressure at the orifice, and a sensor in the shelter converts it to a height. Only the tube and orifice go in the water, which makes bubblers rugged in ice, surf and remote sites, but density and orifice depth must be known accurately.
Bubbler's eating nitrogen, check the orifice line for a leak before the tank runs dry.
Bubbler heights depend on the assumed water density, so a gauge in an estuary with changing salinity can drift with the seasons unless density is measured.
Also heard as
- gas-purge pressure gauge
- bubbler gauge
- gas purge
Related terms
Pressure gauge
A submerged sensor that measures the weight of water above it, converted to water level with density and air pressure.
Tide gauge
An instrument that records water level continuously at a fixed point, the basic tool of tidal measurement.
Tide house
The small shelter on a pier or wharf that houses a tide gauge's well, recorder and electronics.
Station datum
An arbitrary fixed zero set below the lowest expected water at a station, used to record raw water levels.