Daviteq ULA Ultrasonic Level Sensor for Trash Bin
ULA
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1. Introduction
Daviteq ULA ultrasonic level sensor uses ultrasonic technology to measure trash bin levels. The principle is to measure the time of flight of the ultrasound pulse in the air environment. The ultrasound pulse will be ejected from ultrasonic transducer, go through the air and reaching the surface of trash, then reflected back to the ultrasonic transducer. The measuring circuit will measure the time of flight of the Pulse then calculate the distance from transducer to the surface. With advanced digital signal processing technology, the sensor can eliminate unwanted reflected ultrasonic waves. The sensor can be used for trash cans with openable lids where the measured value is not affected during the opening and closing.
The ULA can be integrated into the wireless transmitter from Daviteq, such as Sub-GHz WS433, LoRaWAN WSLRW, and Sigfox WSSFC, to build the complete Wireless Level Sensor. The ULA is also powered by the batteries in the wireless transmitter. The sensor is used to monitor the level of garbage in the trash cans in Office buildings, Hospitals, Schools, Factories... and also for public trash cans of Smart City.
Specification:
Measurement technology: Dual ultrasonic sensor
Measuring range: 30 .. 4500 mm
Resolution & Accuracy: 1.0mm & +/- 10mm+ 0.5% reading
2. Principle of Operation
ULA sensing module emits an ultrasonic pulse from the transmit transducer to the object, and the ultrasonic wave will reflect back to the receiving transducer. The micro-controller will measure the time difference between the sound wave from the transmitting transducer and the receiving reflected sound wave. From that, it calculates the distance by the following formula:
D = ( Time x V ) / 2
Where
D: Distance from the sensor to object surface
Time: the time difference between the wave from the transmitting transducer until receiving the reflected wave
V: velocity of ultrasonic wave in the environment.
The effective detection range of the ULA sensor:
The tested object is the white cylindrical tube, the material is PVC, height is 100cm, diameter is 75mm:
The tested object is the carton board, placed in parallel with the sensor surface, carton board size is 60x50cm:
The smart firmware allows the sensor to filter the wrong echo signal from a rough surface in the trashbin so that it can deliver the accurate average distance or level value.
In addition, it also eliminates the wrong signal when the sensor is moving with the lid during opening (in a short time).
Note: The filter functions can be adjusted by changing the parameter Num_of_Samples. The higher value, the more effective filtering, the higher the energy consumption, and the shorter battery life.
3. Calibration
The Daviteq ULA ultrasonic level sensor measures the distance by taking the air speed of ultrasound in the ambient air. Therefore calibration is not required.
However, in most trashbin level applications, customers need to get the trash level value instead of distance. To do so, the coefficient A & B value is calculated from the height of the trashbin as per the below instructions.
DB: Dead band 0∼300mm (This is a short range in front of the ultrasonic sensor can not measure distances)
H: Maximum measuring distance (Span)
D: Distance
How to determine H value?
Method 1: Based on the design drawing of the trashbin or actual measurement
Method 2: Read the sensor's measurement value when the trashbin is empty (L0). Then H = L0
Note: a₁, b₁ of sensor must be as default when use Method 2. (Default value a₁ = 1, b₁ = 0)
How to determine the new coefficients A and B?
The calibration formula is L = a x D + b. Calibration at 2 points: L = 0 when D = H and L = H - DB when D = DB
The result is A = -1 and B = H and the level formula is L = H - D
4. Application Notes
5. Installation Notes
Make sure the installation environment does not emit gases that harm the transducer (ceramic materials) or the device housing (usually made from Polycarbonate);
Make sure the measured distance must be within the detection range of the sensor;
Do not place the transducer upward to the sky for outdoor application as the rain drops can cause malfunctioning;
Make sure there is no impact on the transducer surface; it will cause the transducer to get damaged;
Do not install the sensor in the closed compartment with solvent vapor or steam; it will cause the wrong measurement.
6. Troubleshooting
7. Maintenance
There are no moving parts or consumed parts in the ULA ultrasonic level sensor. Therefore there is no need to do maintenance.
However, depending on the installation environment, the transducer must be checked and cleaned periodically for accurate measurement.
8. Default Configuration
This ULA Ultrasonic level sensor has the default configuration. The user can change the configuration on the wireless transmitter so that the complete sensor (transducer + wireless) delivers the proper output value. Below are some configuration parameters that store in the flash memory of the wireless transmitter.