Water Level Sensing Methods and Instruments?

4 mn read

Water sensing is crucial in controlling the water flow. Thus, each industry needs a water Flow Sensor to check water levels in the channel or a water reservoir. There are several methods you can use to apply water level sensors to check water levels. Depending on type and design, you can check the levels of water or another liquid in a reservoir, tank, open, or closed channel. 

Industries have used liquid-level sensors for several decades. You’ll find them in firms like chemical industries, food and beverage, pharmaceutical industries, mining, printing, automotive, agriculture, and leak detection at various firms. `


Differential Pressure Transmitters

These transmitters use different pressure heads to gauge the level of water in a channel or reservoir. The height of water determines the pressure at the base. Thus, an increase in height increases the pressure underneath. You’ll find that the tensions at the nodes at different levels change with the amount of liquid.

With a differential pressure transmitter, the pressure at the base of the tank is static. So, the varying pressure is at the surface of the water. The sensor at the surface sends signals to the sensor at the bottom. The signal output is sent to the transmitter. From there, the pressure difference helps to indicate the level of liquid in the tank.

Continuous Float Transmitters

These sensors have a rod supporting the float n or on a liquid. The float gets vibration from the fluid. Then, it sends the pulse up the rod into the sensor. 

One type of these sensors has a magnet that intersects electric pulses from the sensor. Then, the magnet sends back a strain pulse to the sensor. The difference in time between the first signal and the return signal depends on the fluid level in a tank. 

The second type of sensor has a magnet and a rod. But in this case, they have reed switches with resistors. The reeds change the resistance of the circuit when the float rises and falls, closing and opening the switches. 

Radar Level Transmitters

When you need a non-contact sensor to check the level of fluids, then a radar sensor is one of the options. You install the sensor at the top of the reservoir. 

The sensor sends electromagnetic pulses to the surface of the fluids. The vibrations are then sent back to the sensor. The travel time to the surface and back depends on the distance between the sensor and the liquid. 

Radar-level transmitters are best when you use them in non-corrosive liquids. The reason is radar works best when the container is steel. But you can’t use corrosive media with steel. 

It would help if you calibrated the sensor to get rid of errors from false echos. That’s why radar sensors are limited to a single tank used. Were it not for the false echoes, you’d use the sensor to gauge the fluid levels in different tanks and reservoirs. 

Load Cells

With the load cell method, you use the transducer to gauge the weight of the liquid above the sensor. Thus, it would help if you immersed the sensor at the bottom of the tank. The load creates an output signal on the sensor. The signal directly relates to the height of the fluid above the sensor. 

You can get these types of sensors as off-shelf to customize. The off-shelf sensors are very affordable. Customized sensors are costly and very reliable. You can select any based on the needs of your firm.

Ultrasonic Level Transmitters

These sensors work similarly to a radar sensor- The only difference is that it uses sound waves. They are less sensitive to the liquid traits and design of the vessel. Thus, you can use it in all applications. But it would help if you had an advanced way to collect data when dealing with foamy and slurry fluids.

Radio Frequency Capacitance Level Transmitters

This method uses the capacitor’s electrical traits to gauge the fluid level. You can use this method to gauge various levels of fluids and solids in a tank. It happens when all the materials in a tank don’t mix or dissolve. The capacitance of various media differs. Thus, you can use the difference to map out the levels of different fluids. 

The tool design resembles a float-level probe. The difference is that it has a second conductor in place of a magnet. Note that the RF capacitance is affected by the material to be measured, medium, and non-conductive fluids. Thus, the uses are restricted to conductive liquids. 

Tuning Fork 

When you need an alarm point level sensor, a tuning fork may be the sensor. It uses a fork-like node that rotates or tunes as the media passes the sensor. 

The fork vibrates to its natural frequency while on air. However, the frequency drops once you immerse the fork in a fluid. Thus, the tuning fork sensor is an invasive level sensor. 

You fix the sensor at a specific point. If you want to detect full tank level, you fix the sensor near the tip. If you’re going to detect low levels, you should install the sensor lower in the tank. Once the fluid fills the tank, it will go over the fork, sending a signal to turn on the alarm. The action is similar when the liquid drops below the lower sensor’s position. 

Optical

These sensors use LED and phototransistors to gauge the level of fluid in a tank. The LE sends a light signal to the surface of the liquid. Some light bounces back to the sensor. The phototransistor assesses the time the light leaves the sensor and the time it reflects. 

Optical sensors apply to all fluid types and sizes of a tank. Thus, they are applicable in small-scale and large-scale gauging. 

The sensors are compact and with no moving parts. They can operate in extreme temperatures and pressures. Also, you can use them when you have tiny amounts of fluid. However, they are invasive and require a power supply to work. 

Conclusion 

Methods of liquid level sensing differ. They all depend on the type of sensor you use for your application. Check your fluid characteristics and firm’s needs before you settle for one method of level sensing. Also, the vessel material may limit the choice of water flow sensors you can use. 

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