Ultrasonic vs. Capacitive Liquid Level Sensors: Which Technology Fits Your Application?

1.Why Liquid Level Monitoring is More Important Than Ever
2.Ultrasonic Liquid Level Sensors: Measurement Without Contact
3.The BESTAR BPU192000IFBH11 HF: Compact Ultrasonic Performance
4.Technology Comparison: Ultrasonic Level Sensor vs Capacitive Level Sensor 
5.Making the Right Technology Choice

Why Liquid Level Monitoring is More Important Than Ever
The accurate measurement of liquid level is one of the most frequently requested applications in industrial and consumer applications of today. It appears at chemical processing plants where the overflowing tanks can pose a safety threat. It appears in medical infusion devices as a result of which harm has been inflicted on patients if the volume is incorrect. It is present in 'Smart' appliances such as automatic coffee and washing machines in which product quality and energy use is related to the liquid level.
With the introduction of automation in all of these areas, the need for highly reliable, easily maintained and accurate liquid level sensors has greatly increased. The days of simply selecting a sensor technology due to its cost are over. They should think about how the sensor will work for thousands of operating cycles, whether it will need to be calibrated as operating conditions shift, and if it will be effective on the liquids their system uses.
There are two main technologies used in the liquid level measurement market today: capacitive and ultrasonic. Under the proper operating conditions, both can measure the liquid level with accuracy. However, they have different physical principles and can really separate under extreme conditions and when dealing with variable or aggressive liquids.
In this blog, you'll get an explanation of how each technology can be used and what real-world limitations exist in both. It also provides a practical example of an ultrasonic sensor, the BESTAR BPU192000IFBH11 HF ultrasonic liquid level sensor.

Ultrasonic Liquid Level Sensors: Measurement Without Contact
How They Work
The operation principle of ultrasonic liquid level sensor is extremely simple. The sensor sends out a brief pulse of high frequency sound waves towards the surface of the liquid. That pulse moves through the air above the liquid, hits it and bounces back to the sensor. The sensor records the time it takes for the returning echo to return. The time taken is known as time of flight(ToF). The speed of sound in air remains the same for known conditions and the time of flight measurement is converted directly to a distance. This distance is enough to let the system know exactly how far the liquid surface is from the sensor, which equals the liquid level.
The measurement is taken without the sensor coming into contact with the liquid. The most important feature of ultrasonic liquid level sensing is that there is no contact between the sensor and the liquid. The sensor is placed above the liquid, its line of sight is downward, and only the sound wave gets in touch with the surface of the liquid.
The importance of measuring things without making physical contact.The value of non-contact measurement.
A sensor that comes in contact with the liquid in systems where the liquid is corrosive, viscous suspended particles or is frequently changed with liquids of varying compositions causes reliability issues. Deposit build up on contact sensors. They corrode. They need to be cleaned or replaced periodically. They can make the liquid that they are measuring dirty. All these problems are overcome by ultrasonic sensors since the sensing element does not come in contact with the liquid.
As well as this non-contact measurement also means that the sensor does not require an installation inside the tank or vessel. It can be installed on the top of the liquid path of the tank, making the maintenance simple and its installation easy.

The BESTAR BPU192000IFBH11 HF: Compact Ultrasonic Performance
BESTAR BPU192000IFBH11 HF is an ultrasonic liquid level sensor for the environments where space is limited and reliability is indispensable. There are a number of features that make it worthwhile exploring in detail.
The sensor is waterproof. The surrounding area of the sensor is usually wet when used to measure liquid. The sensor parts are also exposed to moisture during condensation, splashing and cleaning cycles. A waterproof construction is one that operates reliably in all conditions. The BPU192000IFBH11 HF is also RoHS compliant. The sensor is compact and light. There are many applications that require very precise liquid level monitoring within an equipment where every cubic centimeter is used. The sensor with a large area to be mounted or the sensor that needs a deep probe assembly is simply not possible in these designs. The BPU192000IFBH11 HF is scaled to fit the application where space is restricted but mechanical layout is not affected.
The sensor has high sensitivity and low power consumption. The higher the sensitivity, the more accurately it can determine the surface of the liquid even when the signal returns occurs with less intensity. It is also low power consumption which makes it applicable for battery powered equipment and always on monitoring applications in which energy budget is a critical constraint.
The best combination of these features is responsible for the BESTAR BPU192000IFBH11 HF being a practical option for high precision liquid level measurement in medical applications, small industrial instruments and smart consumer goods.

                                                                                                                                                                                                                       If you want to know this product, please contact us.

Technology Comparison: Ultrasonic Level Sensor vs Capacitive Level Sensor
An ultrasonic liquid level sensor works by reflecting sound waves off the liquid's surface to detect the level. Does not measure an electric parameter of the liquid. All the measurements are independent of the dielectric constant, conductivity, viscosity and chemical composition of the liquid. The ultrasonic sensor can read the surface of water, oil, acid, alcohol or a combination of many fluids in the tank.
Capacitive sensor responds correctly only to the liquid that it was calibrated against. Replace the liquid but the reading does not change. That's a small drawback, but not inconsequential. It's a basic limitation that dictates whether or not capacitive sensing is practical in an application or not.
Reliability and Maintenance
The non-contact ultrasonic sensor has no part of the electrodes exposed to the medium. No parts to corrode, no parts to foul and no parts to clean on a regular basis in the liquid path. The acoustic element is housed in the sensor canning. Does not deteriorate with changing liquid.
In many liquid environments, there's a capacitive sensor with direct contact electrodes which will form deposits over time. The presence of cleaning cycles complicates things up. Contact based capacitive sensing has practical challenges not encountered in ultrasonic measurement, especially when cleaning is difficult or contamination of the fluid in the held section can't be tolerated.
Low power consumption and small size
New liquid level application of high accuracy, such as medical devices and smart appliances, demands sensors which offer minimal power consumption and low dimensions within the specified dimensional envelope. These are the requirements which were considered during the design of BESTAR BPU192000IFBH11 HF. The low power consumption and small housing of this sensor make it convenient for use in battery-powered and space-limited designs where larger or more-powerful sensors could not be used.
Comparison Summary

Making the Right Technology Choice
For multi-liquid systems, or if your liquid concentration changes regularly (through dilution, contamination or specifically replacing liquids), ultrasonic liquid level sensor makes more sense. No account is taken of the contents of the tank. Measuring the surface position and not anything more. 
When the application includes one, well-defined, liquid component in a controlled area where the installation configuration allows to use a sensing geometry convenient with a wall mounting, a capacitive sensor can be used successfully. The important consideration is to ensure that acceptable measurement drift during the service life of the product is not caused by the anticipated composition and temperature of the liquid.
The selection of a liquid level transmitter is not just a decision made with respect to the accuracy of the measurement. It's a matter of system design. The reliability of the monitoring system over its service lifespan is determined by the choice of measurement technology and by having access to a supplier robust enough to provide support for integration and production.
BESTAR offers not only products but also solutions to ensure optimal sensor performance in end-use applications; please contact BESTAR if you have requirements for ultrasonic liquid level sensors.