Ultrasonic Sensor Technology
Madison's ultrasonic level sensors rely on high-frequency sound waves above the range of human hearing (over 20,000 hertz) to measure level. Our ultrasonic sensors use ultrasonic sound waves to sense the level of liquids, solids or powders in airbased containers, tanks and vessels of all sizes and shapes.
Madison's sensors can be bench- or field-calibrated through communications with a PC or a push button on the sensor. This capability enables the user to define the span in the vessel and only trigger on objects within that window. Each standard model has its defined operating distance listed on the catalog chart page. Custom models can be designed for specific application needs based on the variables that can be found on the Madison Specification Work Sheet.
These ultrasonic sensors are not susceptible to error due to the target material's color, shape or composition (e.g., transparent or opaque, liquid or solid). They are particularly good for applications that must sense a non-metallic object in an environment where there is systematic, heavy wash down, liquid, dust, heavy spray, food, ink, or other environmental hazards. Since sound energy is used for detection, the reflecting object does not have to be metal, but can also be glass, plastic or even paper.
Stagnant, non-agitated liquids and solids consisting of large and hard particles are good reflectors and, therefore, good candidates for ultrasonic level measurement. Fluff, foam and loose dirt are poor reflectors, and dust, mist or humidity in the vapor space tend to absorb ultrasonic pulse. When these conditions are present, they are generally not measurable. As a rule of thumb, use 20% of the stated range of a Standard model to see if it will overcome these conditions. Where these characteristics are present, a Madison radar sensor might be appropriate.
Architecture of an Ultrasonic Level Sensing Device:
Operation Principle of Ultrasonic Level Devices:
An ultrasonic transducer matched to air is stimulated by a pulse transmitter, and it generates a pressure wave that propagates to a target and then reflects (in similar fashion to a loudspeaker). The reflected wave is received by the same transducer, in the receiver mode, and is converted into an electrical signal (as a microphone would). The electrical signal is amplified and processed to find the reflected echo and then calculated to find the distance to a specific target. Distances to a target are converted linearly to a 4-20 mA current and, optionally, information about level measurement is sent via RS232 or RS485 to a PC for processing such functions as diagnostics, programmble set-up and data logging.
Ultrasonic Sensor Still-Pipe Mounting Considerations:
The ID of the pipe must be greater than the OD of the transducer nozzle. If pipe is longer than 6", a 45° cut is required.
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