Flowmeter Selection: open_channel
Flowmeter selection guide covering 16 meter types across 6 categories (differential_pressure, velocity, mass_flow, electromagnetic, positive_displacement, variable_area, open_channel) — each record documents accuracy (% reading or full-scale), rangeability, pressure drop class, fluid compatibility, installation straight-run requirements, and relative cost class
| meter category | meter type | accuracy basis | accuracy pct reading (%) | cost class | cost relative | fluid compatibility | fluid phase | fluid restrictions | installation notes | measurement principle | moving parts | notes | pressure drop class | pressure drop notes | rangeability | rangeability num | requires power | temp limit C max (degC) | temp limit C min (degC) | typical applications | typical pipe size in max (in) | typical pipe size in min (in) |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| open_channel | flume_parshall | percent_of_reading | 5 | low | 1 | Open channel - wastewater, irrigation; tolerates solids and sediment | liquid | Requires free-flow (submergence less than 0.7); calibration specific to throat width | Self-cleaning; primary device built into channel; ultrasonic or float sensor measures head | Parshall flume throat constriction head-to-flow power law | no | ISO 9826; throat widths 1 in to 50 ft standardized; submerged-flow correction per Parshall tables; preferred over weir for solids-laden flows | none | Small energy loss - flume creates hydraulic drop | 50:1 | 50 | yes | 50 | -10 | Municipal WWTPs, irrigation canals, stormwater monitoring, industrial effluent | 1,000 | 0.01 |
| open_channel | weir_rectangular | percent_of_reading | 5 | low | 1 | Moderate-to-large open channel flows - canals, rivers, large wastewater | liquid | Requires pool; sediment accumulates behind crest | Full-width or contracted rectangular weir; end contractions reduce effective length | Rectangular notch weir head measurement (Francis formula Q=Cd*L*H^1.5) | no | ISO 1438; Cipolletti trapezoidal weir (sides 4V:1H) combines rectangular and V-notch features; accuracy degrades when H/L greater than 0.5 | none | Full head loss equals upstream head (open channel) | 10:1 | 10 | yes | 50 | -10 | Irrigation, river gauging, large effluent channels, canal flow measurement | 1,000 | 0.1 |
| open_channel | weir_v_notch | percent_of_reading | 3 | low | 1 | Low-flow open channel - clean or slightly turbid water | liquid | Requires pool upstream; trash or debris accumulates in V notch; not suitable for high-solids or wastewater with floatables | Level sensor (float or ultrasonic or pressure) upstream of weir plate; stilling well recommended | V-notch weir head measurement (Francis/Thompson formula Q=Cd*(8/15)*tan(theta/2)*sqrt(2g)*H^2.5) | no | ISO 1438; 90 deg and 45 deg notch most common; best accuracy at low flows due to high H exponent; head greater than 60 mm for accuracy | none | Full head loss equals upstream head (open channel - no pipe) | 500:1 | 500 | yes | 50 | -10 | Irrigation canals, streamflow gauging, laboratory, small WWTPs, industrial effluent | 10 | 0.01 |
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