The Flow Rate Sensor measures the velocity of water in a river, stream, or canal. It can be used to study the discharge, flow patterns, and sediment transport of a stream or river.

Note: Vernier products are designed for educational use. Our products are not designed nor are they recommended for any industrial, medical, or commercial process such as life support, patient diagnosis, control of a manufacturing process, or industrial testing of any kind.

What's Included

Compatible Software

Quick Start

Using the Product

1. Connect the Flow Rate Sensor to the interface and start the data-collection program.
2. Collect stream flow data
   1. Change the mode to Selected Events. Check the box to average over 10 seconds.
   2. Submerge the impeller of the Flow Rate Sensor to about 40% of the depth measured at each section. If necessary, use the plastic risers that are included with the flow rate sensor to support the sensor on the stream bed. The risers make it easier to keep the impeller of the sensor in the same spot and oriented in the same direction.
   
   3. Start data collection. Point the impeller of the sensor upstream (as shown below) and directly into the flow and click or tap Keep. Hold the sensor in place for 10 seconds while data are being collected. Once data collection is finished, the flow rate will be displayed.
   
   4. Move to the next sampling site and click or tap Keep.
   5. When done, click or tap Stop to end data collection.

Calculating Discharge

To determine the amount of water flowing in a stream, you need to measure the rate at which the water flows and the area the water occupies at a specific point in the stream. The discharge, or stream flow, is the flow rate multiplied by the area of water.

Flow Rate × Area of Cross Section = Discharge or Stream Flow

Detailed instructions are found in our Water Quality with Vernier lab book, www.vernier.com/wqv

Sediment Transport

The amount of sediment and maximum particle size that can be transported by moving water is related to the flow velocity. Therefore, flow velocity data obtained using the Flow Rate Sensor can be used to determine what size particles will stay in motion at a particular flow velocity. This chart, derived from accumulated observed data, shows that for a given flow velocity there is a range of behavioral possibilities for sediment particles lying on the bed, or entrained within the flow, of a stream.

At a measured flow velocity of 1 m/s, silt and sand (though not compacted clay) will be eroded from the stream bed and transported downstream. At the same velocity, all sediment particles between 10 mm and 100 mm that were already in motion will continue in motion. Particles greater than 100 mm will be deposited. A Flow Rate Sensor can be a valuable observational tool when used in sediment transportation studies.

Describing Flows

Using the Flow Rate Sensor, it is possible to map flow characteristics of a stream by taking measurements at different spots and depths. To understand the flow characteristics within streams of moving water, it is helpful to construct Stream Lines and Vector Lines. The illustration shown here shows how Stream Lines depict possible paths of a single fluid particle.

Vector Lines represent both the flow rate and direction. The longer and broader the line, the greater the flow velocity. Vector Lines convey useful information about the stream flow characteristics.

Videos

Calibrating the Sensor

You do not have to perform a new calibration when using the Flow Rate Sensor. The sensor is calibrated prior to shipping.

Specifications

Care and Maintenance

How the Sensor Works

The Vernier Flow Rate Sensor measures the velocity of flowing water. When placed in a stream, as shown here, water flows against the blades of the impeller, causing it to turn. The faster the water flows, the faster the impeller turns. A bar magnet rotating with the impeller triggers a reed switch with each half rotation. The switch sends a pulse to the signal conditioning box, where the pulses are converted into a voltage that is proportional to flow rate. Flow rate can be measured in m/s or ft/s.

Tips

1. The plastic risers that come with the Flow Rate Sensor can be very helpful in keeping the sensor at the same orientation while taking measurements. When using the risers, simply place the bottom of the sensor rod against the stream bottom. If you are unsure which riser to use, start with the medium riser first and gauge the depth from there.

   
2. When students are selecting sites to take flow measurements, they should choose a site where the stream is not split by rocks, partially submerged obstructions, or sand bars.
3. The impeller of the flow rate sensor should always be pointing into the flow when measurements are being made. Students need to stand on the shore when taking measurements close to the shore, or stand as far downstream as possible from the sensor when placing the sensor in deeper water.
4. Because stream flow is easily affected by weather conditions, it is important that good notes concerning date, time, and weather be taken whenever flow measurements are made.

Troubleshooting

Safety

1. Follow safety guidelines when students are working in or near water. Avoid sites where the water is deep or swift. Water with a flow velocity of 0.5 m/s or greater is considered to be swift. Water with a depth greater than the top of your knee should be considered deep.
2. Never work alone around a stream. Students should always work with others in groups of 2–3. Do not allow students to wander away from their group. It is important to know where student groups are at all times. Students should not change locations without notifying their instructor first.
3. Before using a particular site, it is best to survey the area for unseen dangers, such as unstable banks, dangerous obstacles in the stream, or fallen trees. Avoid these possible dangers.
4. Always be careful when crossing a stream. If it looks dangerous, select another spot in the stream to cross.
5. Students should wear warm, waterproof clothes when working in a stream. If possible, they should bring spare items such as dry socks that can be worn after working in the water. Prolonged exposure to cold waters can result in hypothermia, which can be a life-threatening condition.

Repair Information

Warranty

Warranty information for this product can be found on the Support tab at www.vernier.com/flo-bta/#support

General warranty information can be found at www.vernier.com/warranty