Non contact level sensors refers to level sensor can measure level without contacting liquids. Non contact level sensors have been made on different technologies,e.g. ultrasonic, radar,optical, capacitive,etc. Non contact measurement way provides many kinds of advantages, e.g. no moving parts, no liquid contacting, no pollution to fluid, smaller size body, longer life, lower cost for certain application, suitable for acid and alkali and corrosive fluid(part of models), no cutting and no opening (part of model),etc.
Non contact level sensors mainly have 2 kinds of working ways: one is non contact,but level sensor and level should be face to face, the other way is measuring from external surface of container. For the former, it mainly has ultrasonic level sensor and radar level transmitter, and for the latter, the typical is capacitive level sensor,ultrasonic level sensor and optical level sensor.
In order to show the difference, we can call them non contact and external working ways and here lists working principle diagram of the 2 working ways as below:
A. Non-contact working in air environment, and typical technologies have ultrasonic level sensor and radar level transmitter. This working way usually requires vertical installing way on top of container(radar level also supports side mounting for several application), and when used for closed container, it requires to cut a hole to install related level probe. This way is mainly used higher level test, e.g. 1 meter and above. This is usually for continuous level measurement.
B.External way from external surface, and typical have capacitance level, ultrasonic level and optical fiber level. This way can be used for open and closed container. Level probe is installed on external surface of various containers, e.g. tank, bottle, drum, etc. It requires to make level probe to contact container surface closely without any gap space. This way is completely isolated from inner liquid and provide unique solution for many projects. It usually requires side mounted and mainly used for point level monitoring.
There are 5 main types of non contact level sensors which are main using models. Thus, we will mainly introduce them as below:
1. External Capacitive Non Contact Level Sensor
Non contact water level sensor or non contact level switch is developed on the principle of capacitance technology. The non contact level sensors are used for non metal containers and it features a very low cost and small size body. The level sensors are very suitable for large quantity application with lower cost. It can be used for non-metal containers, e.g. plastic, glass, porcelain, etc. One of its main deciding factor is wall thickness of container. Take plastic container as example, there may be several wall thickness ranges: 3mm, 10mm,20mm,30mm, and even 100mm. For more information, please visit our non contact water level sensor.
2.External Optical Non Contact Level Sensor
Optical infrared non contact level sensor is mainly developed for tube level monitoring. Its often range of tube diameter is below 13-15mm. It may be easily effected by light and color. It senses the liquid level by sending/receiving of infrared light. Our infrared level sensors have sending/receiving integrated together. When power sensor on, its infrared light is produced to detect solid or liquid level, then reflected back to receiving unit. By this, infrared level sensor switch can monitor level. It doesn't require to be installed on container surface closely. But it may be easily influenced by sun light, meanwhile, it requires bigger installing space. The infrared sensors are also used for other industries, e.g. product counter, goods positioning, solid level test, etc.
3.External Optical Fiber Level Sensor
Optical fiber level sensors have 2 kinds of combination ways.
One is use 2 pieces of optical fiber probes and make them beam detector. When level reach beam level, there is a signal, when level is down, there is another different signal.
The other is integrated with sender and receiver. It has compact structure and usually used for tube level/flow checking.
4. External&Non Contact Ultrasonic Level Sensor
Ultrasonic level sensors can support the 2 kinds of working ways. Of course, non contact model and external model have different working structure. Usually, external working model is more expensive than non contact model.
When use as non-contact way, it is often used for tank or open place, e.g open channel, pool, small river, etc. For closed tank or other containers, it requires to but hole on top of containers so that ultrasonic level sensors can be inserted to detect level. Such application is usually used for higher level measurement, e.g. at least 1 meter or higher.
The other is clamp on way which requires ultrasonic level sensors to be installed on side or bottom of containers. Such technology utilizes ultrasound sonar echo principle which is different from non contact ultrasonic level above. Side mounting is used as level switch for point level, and bottom installing is used for continuous level measurement. For such type, its price may vary sharply.
5.Non Contact Radar Level Transmitter
Radar technology is firstly used for army and then gradually transferred to common using. Radar wave belongs to electromagnetic wave which is more stable than ultrasound wave. Thus, radar level is more stable than ultrasonic level. Ultrasonic level are often used for liquid under common condition, but radar level is often used in harsh application. Radar level is often used for solid level measurement and when used for liquid, it is usually used for oil tank or big river, etc. But radar level always have a higher cost and many common projects can't afford it.
Each type non contact level sensor has its unique advantage and no one can meet all of requirement, thus user should select proper type as the detailed application. But usually ultrasonic and capacitive non contact liquid level sensor should be first 2 considerations while non contact level measurement are required.