Detectors For Openchannel Sensors

The level rise generated by flumes or weirs can be measured by any level detector including simple devices such as air bubblers.

The flow in open channels can also be detected without using flumes, weirs, or any other primary devices. One such design computes flow in round pipes or open channels by ultrasonically measuring the depth, calculating the flowing cross-sectional area on that basis, and multiplying the area by the velocity to obtain volumetric flow (see Figure 7.6.16).

Another open-channel flowmeter that does not need a primary element uses a robotically operated magnetic flowmeter probe to scan the velocity profile in the open channel (see Figure 7.6.17). In this design, the computer

FIG. 7.6.16 Volumetric flow computer measuring depth and velocity in an open channel without a primary device. (Reprinted, with permission, from Montedoro-Whitney Corp.)

FIG. 7.6.17 Robotically operated magmeter probe sensor used to compute channel flow. (Reprinted, with permission, from MSR Magmeter Mfg. Ltd.)

FIG. 7.6.15 Dual-range Parshall flume. (Reprinted, with permission, from Fischer & Porter Co.)

FIG. 7.6.17 Robotically operated magmeter probe sensor used to compute channel flow. (Reprinted, with permission, from MSR Magmeter Mfg. Ltd.)

algorithm separately calculates and adds the flow segments through each slice of the velocity profile as the velocity sensor moves down to the bottom of the channel.

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