For many people, a āliquid level sensorā is synonymous with āfloat switch.ā Traditional float switches work thanks to a magnetic reed, breaking or connecting an electrical circuit when liquid levels reach a specified point via a specialized float. For most applications where liquid levels need to be measured within a tank or other vessel, float switches work perfectly, especially considering the variety of custom optionsāmounting position, chemical compatibility, and more.
The Need for Sensors without Moving Parts
For some applications, particularly those which involve viscous liquids or other difficult materials, traditional float switches might not be appropriate. This is because difficult materials can interfere with the free motion of switch floats. When the float canāt move, the switch doesnāt work. For instance, with a typical normally-open horizontal float switch, sludge or other debris could accumulate or become lodged in the space between the float and stem. This would prevent the switch from activating.
Sensor Options with No Moving Parts
Luckily, for such difficult applications, there are a number of options of switches that donāt require moving parts. Here are two of the most popular, each offered by SMD Fluid Controls.
Optical Liquid Level Sensors
Optical liquid level sensors use infrared light for point-level detection. The sensor tip emits an infrared light outward, which then returns to the sensor in the absence of any barrier.
When the sensor is immersed in water, however, the light is dispersed and does not return. Therefore, the sensor can tell when liquid levels have reached beyond a certain point based on whether it is receiving incoming infrared light.
Ultrasonic Liquid Level Sensors
Whereas optical sensors use light, ultrasonic sensors use sound. Mounted at the top of a tank or vessel, ultrasonic liquid level sensors emit an ultrasonic pulse toward the surface of the liquid medium being measured. As with optical sensors infrared light, this sound pulse bounces back and returns to the sensor.
Based on the speed of sound and the length of time this return trip takes, the sensor can calculate the distance between itself and the liquid surface.
In addition to working with no moving parts, ultrasonic sensors also offer non-contact level measurement, and continuous level measurement.
Submersible Hydrostatic Pressure Sensors
Finally, SMD Fluid Controls offers downhole submersible liquid level sensors that operate via hydrostatic pressure sensing.
The sensor sits at the bottom of a tank or vessel with a long lead line. Based on the pressure exerted on it by the liquid medium above, the weight and therefore volume can be determined. Along with the total vessel capacity, this can be used to calculate internal liquid levels.
Liquid Level Sensors from SMD Fluid Controls
Based in the United States and the United Kingdom, SMD Fluid Controls offers a variety of standard and custom liquid level sensing solutions, including OEM and design services. No matter what your application calls for, SMD can help.