Open Channel Flow Sensors
Open channel flow is any flow through a ditch or conduit that is not pressurized. We offer other sensors and meters for a pressurized system. It is very common to use flumes or weirs in open channel ditches.
Open Channel Flow Meters
Area Velocity flow sensors can be installed in the bottom of a ditch, channel, or pipe culvert. They use ultrasonic pulses to measure both the depth and the velocity of the water which gives the ability to calculate flow (discharge). These systems are very convenient, due to a simpler installation, and can save money based on the time it may take to install a flume or weir. An additional benefit is that once the sensor is installed the flow rate data is recorded to a digital file for future review or for water use decisions.
How does an area velocity sensor work?
Also, known as an AVFM or Area Velocity Flow Meter.
Watch this video, to your right, that is provided by Greyline Instruments.
Water Velocity Sensor & Water Depth Sensor – Bigfoot
Mount the Bigfoot flow sensor on the bottom of a pipe or channel to measure both water level and water velocity. This sealed, ultrasonic sensor provides a solution for continuous water measurement in open channels and partially filled pipes. No calibration is required. The Bigfoot can be powered from solar charging systems using DC power supplies. The 4-20 mA outputs can be connected to dataloggers, SCADA systems or PLC measuring systems, we like to use the CR300 or CR850.
Flow can be calculated from the Bigfoot transmitter outputs by using the formula:
CFS Flow = Area (square feet) x Velocity (Feet per/second), where Area is the cross-sectional area of the channel at the level measured by the Bigfoot, and Velocity is the speed of the water. It can be mounted in irrigation pipes, channels, turn-outs, ditches, or culverts with defined dimensions. The Bigfoot is designed to provide water level and water velocity measurements in irrigation open channel applications and storm water applications which typically have well defined channels for more accurate area calculations.
Bigfoot Area Velocity Sensor Specifications:
- Level Range: 1.8 to 144 in (45.8 to 3658 mm) from bottom of sensor
- Velocity Range: 0.1 to 9.84 ft/s (0.12 to 3.0 m/s)
- Outputs: 4-20 mA Velocity and 4-20 mA Level, 1000 ohm at 24 VDC
- Power Input: 10-26 VDC, 150 mA Max.
- Operating Temperature: 32° to 150° F (0° to 65° C)
- Accuracy: Level: ±0.25% of actual Range or 0.04 in (1 mm), whichever is greater
Velocity ±2% of reading or ±0.02 ft/s, whichever is greater
What does the Bigfoot do?
Measure velocity of water
Measure depth of water
Measure flow in open channels and culverts.
Click Image to Enlarge
Remote Data Collection & Monitoring
We recommend using the Campbell Scientific datalogging systems to measure and record the Bigfoot sensor data. By using the Campbell Scientific systems you can create remote networks that measure flows and report back to a central PC at a home or office, or you can send the data to the cloud and access your flow information on a website. The Campbell Scientific systems require very low power, we usually use batteries with solar recharge to create the remote monitoring network. We can help you create these kinds of systems. Options for remote data collection are cellular, radio, satellite, WiFi and wired networks. We can use a combination of these technologies to create a custom data collection network to meet your needs.
Pulsar AVFM 6.1 Area-Velocity Flow Meter
The AVFM (Area Velocity Flow Meter) will monitor flow through open channels, partially full sewer pipes and surcharged pipes. Ideal for storm-water, combined effluent, raw sewage and irrigation water. The AVFM 6.1 uses a submerged ultrasonic sensor to continuously measure both Velocity and Level in the channel. There are no moving parts to wear, foul or clog.
View flow rate and total flow on the large back-lit LCD display and connect to external devices with three 4-20mA outputs and two control relays.
System Specifications:
- 0.1 to 20 ft/sec (0.03 to 6.2 m/sec) and reverse flow to -5 ft/sec (-1.5 m/sec)
- Minimum Head: 1 in (25.4 mm). Maximum Head: 15 ft. (4.57 m)
- 5°F to 175°F (-15 to 80°C)
- 316 stainless steel, epoxy resin, polyurethane (sensor cable)
Download the brochure for the full specification list.
Fluvia RC3 – Water Velocity Meter
The FLUVIA RC3 flow meter is a portable electromagnetic device that measures the velocity of water to determine its flow.
Its hydrodynamic shape and small probe size permits measurements close to a fluid surface, channel bed or pipeline wall, and with no moving parts, it does not retain debris – guaranteeing accuracy and reliability.
The FLUVIA RC3 can be tailored to the user’s ideal setup, meaning the units, date and time, language and data logging methods are easily changeable. An optional extra of GPS is also available which would auto set the time as well as provide accurate location information for each data point.
Key Features
– Electromagnetic sensor unaffected by temperature variations, density changes, sediment and water clarity
– IP67 Environmental Rating
– Hands-free operation
– Rechargeable, 20hrs continuous use battery life
– GPS, Bluetooth and GSM (Cellular network) support
– Two sensor types are available
– Recording of up to 12,000 data points
FloStick by Aqua Data
The FloStick electromagnetic water velocity flow meter is a portable device that measures the velocity of water to determine a flow rate. The electromagnetic sensor is unaffected by temperature variations and density changes. Sediment or water clarity does not effect accuracy.
The probe length is fixed and there is no assembly to begin taking measurements. The FloStick will display the velocity of the water in real-time to assist with
calculating flow discharge.
Simply remove the FloStick from the carry bag and it
is ready to go!
Specifications:
• 0 – 6.56 FPS velocity range (Option for 9.84 FPS)
• Records 2,000 data points
• Lithium-ion Rechargeable Battery
• Electromagnetic Sensor (Faradays’ Law)
• Resolution 0.003 FPS
• Accuracy 2% of maximum velocity
• Minimum required depth 1-1/4 inch of water
• Probe handle is 2.95 ft
• FloStick will float if dropped
• Lifetime calibration
Select image above to watch video on how to use a velocity meter to measure flow in a stream or ditch.
Open Channel Flow using Level Only – Flow Rating
We offer water level sensors, which can be integrated with a datalogger or PLC and then configured to “calculate” flow in ditches or non-pressurized conduits. This option is often called a rated section or rated flow. This is only recommended if an estimated flow rate will be acceptable.
This rating procedure requires flow to be manually measured using a device like the flow probe or Fluvia meter shown above. Once water velocity has been measured at different depths in the channel you can build a rating table that uses depth to estimate the flow rate. This can be done with a polynomial equation.
Consider contracting with our company to come to your location and create a flow rating table, this often takes multiple site visits. One consideration to this option is that vegetation and silting of the channel can affect this calculation throughout the season, and over the years.
This option called a rated channel or rated section is commonly used by the USGS on larger rivers. The rating should be updated frequently so that the accuracy of the flow measurement is maintained over time.
Watch the “Flow Probe” video above to see what is required to make a rating of a stream, canal or other open channel flow site.
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