There are three main technologies used to measure flow in open channel primary devices (flumes and weirs): ultrasonic, bubbler, submerged probe / pressure transducer. Each technology has it own advantages and disadvantages.
A summary of these can be found below.
Ultrasonic
- Not recommended for channels less than 6-inches [15.24 cm]
- Excellent suitability with measuring irrigation channels and small streams
- Excellent suitability with measuring rivers and large streams
- Compatible with all chemicals (no vaporous) in a flow stream
- Affected by strong wind
- Generally good resistance to normal air temperature fluctuations - although large temperature differentials may cause errors
- Affected by steam
- Affected by foam
- Affected by stream turbulence
- Affected by floating debris
- Affected by floating oil and grease
- Excellent performance with suspended solids
- Excellent performance with suspended oil and grease
- Excellent performance with silting
- Very good performance with normal liquid temperature fluctuations - although large liquid temperature differentials may cause errors
- Maintenance is not increased by the presence of silting, suspended solids, or high grease concentrations
Bubbler
- Excellent suitability with channels less than 6-inches [15.24 cm]
- Excellent suitability with measuring irrigation channels and small streams
- Excellent suitability with measuring rivers and large streams
- Compatible with all chemicals in a flow stream (very compatibility of bubbler tube, though)
- Not affected by strong wind
- Generally good resistance to normal air temperature fluctuations - although large temperature differentials may cause errors
- Not affected by steam
- Not affected by foam
- Not affected by stream turbulence
- Not affected by floating debris
- Not affected by floating oil and grease
- Good performance with suspended solids (increased bubble rate may be required)
- Good performance with suspended oil and grease (increased bubble rate may be required) (avoid pre-DAF applications)
- Good performance with silting (increased bubble rate may be required)
- Excellent performance with normal liquid temperature fluctuations - although large liquid temperature differentials may cause errors
Submerged Probe / Pressure Transducer
- Excellent suitability with channels less than 6-inches [15.24 cm]
- Good suitability with measuring irrigation channels and small streams
- Excellent suitability with measuring rivers and large streams
- Poor compatibility with organic solvents, organic acids, esters, inorganic acids, inorganic bases, and inorganic salts
- Not affected by strong wind
- Excellent performance with normal air temperature fluctuations
- Not affected by steam
- Not affected by foam
- Not affected by stream turbulence
- Not affected by floating debris
- Not affected by floating oil and grease
- Very good performance with suspended solids (increased bubble rate may be required)
- Very good performance with suspended oil and grease (increased bubble rate may be required) (avoid pre-DAF applications)
- Very good performance with silting (increased bubble rate may be required)
- Good performance with normal liquid temperature fluctuations - although large liquid temperature differentials may cause errors (avoid laundry applications)
- Occasional maintenance is required by the presence of silting, suspended solids, or high grease concentrations
Source: 4200 Series Flow Meters, L-2107, Teledyne ISCO, Inc., January 2007.
