Sords Electric sells Ultrasonic Sensors and switches. Ultrasonic sensors use sound waves for sensing.
Ultrasonic sensors are commonly used for a wide variety of noncontact presence, proximity, or distance measuring applications. These devices typically transmit a short burst of ultrasonic sound toward a target, which reflects the sound back to the sensor. The system then measures the time for the echo to return to the sensor and computes the distance to the target using the speed of sound in the medium [1,2,3].
The wide variety of sensors currently on the market differ from one another in their mounting configurations, environmental sealing, and electronic features. Acoustically, they operate at different frequencies and have different radiation patterns. It is usually not difficult to select a sensor that best meets the environmental and mechanical requirements for a particular application, or to evaluate the electronic features available with different models. Still, many users may not be aware of the acoustic subtleties that can have major effects on ultrasonic sensor operation and the measurements being made with them.
The overall intent of this article is to help the user select an ultrasonic sensor with the best acoustical properties, such as frequency and beam pattern, for a particular application, and how to obtain an optimum measurement from the sensor. The first step in this process is to gain a better understanding of how variations in the acoustical parameters of both the environment and the target affect the operation of the sensor. Specifically, the following variables will be discussed:
• Variation in the speed of sound as a function of both temperature and the composition of the transmission medium, usually air, and how these variations affect sensor measurement accuracy and resolution • Variation in the wavelength of sound as a function of both sound speed and frequency, and how this affects the resolution, accuracy, minimum target size, and the minimum and maximum target distances of an ultrasonic sensor • Variation in the attenuation of sound as a function of both frequency and humidity, and how this affects the maximum target distance for an ultrasonic sensor in air • Variation of the amplitude of background noise as a function of frequency, and how this affects the maximum target distance and minimum target size for an ultrasonic sensor • Variation in the sound radiation pattern (beam angle) of both the ultrasonic transducer and the complete sensor system, and how this affects the maximum target distance and helps eliminate extraneous targets • Variation in the amplitude of the return echo as a function of the target distance, geometry, surface, and size, and how this affects the maximum target distance attainable with an ultrasonic sensor
Fundamental Ultrasonic PropertiesUltrasonic sound is a vibration at a frequency above the range of human hearing, usually >20 kHz. The microphones and loudspeakers used to receive and transmit the ultrasonic sound are called transducers. Most ultrasonic sensors use a single transducer to both transmit the sound pulse and receive the reflected echo, typically operating at frequencies between 40 kHz and 250 kHz. A variety of different types of transducers are used in these systems [4]. The following sections provide an overview of how the sound pulse is affected by some of the fundamental ultrasonic properties of the medium in which the sound travels.
Speed of Sound in Air As a Function of Temperature In an echo ranging system, the elapsed time between the emission of the ultrasonic pulse and its return to the receiver is measured. The range distance to the target is then computed using the speed of sound in the transmission medium, which is usually air. The accuracy of the target distance measurement is directly proportional to the accuracy of the speed of sound used in the calculation. The actual speed of sound is a function of both the composition and temperature of the medium through which the sound travels (see Figure 1).
The wide variety of sensors currently on the market differ from one another in their mounting configurations, environmental sealing, and electronic features. Acoustically, they operate at different frequencies and have different radiation patterns. It is usually not difficult to select a sensor that best meets the environmental and mechanical requirements for a particular application, or to evaluate the electronic features available with different models. Still, many users may not be aware of the acoustic subtleties that can have major effects on ultrasonic sensor operation and the measurements being made with them.
The overall intent of this article is to help the user select an ultrasonic sensor with the best acoustical properties, such as frequency and beam pattern, for a particular application, and how to obtain an optimum measurement from the sensor. The first step in this process is to gain a better understanding of how variations in the acoustical parameters of both the environment and the target affect the operation of the sensor. Specifically, the following variables will be discussed:
• Variation in the speed of sound as a function of both temperature and the composition of the transmission medium, usually air, and how these variations affect sensor measurement accuracy and resolution • Variation in the wavelength of sound as a function of both sound speed and frequency, and how this affects the resolution, accuracy, minimum target size, and the minimum and maximum target distances of an ultrasonic sensor • Variation in the attenuation of sound as a function of both frequency and humidity, and how this affects the maximum target distance for an ultrasonic sensor in air • Variation of the amplitude of background noise as a function of frequency, and how this affects the maximum target distance and minimum target size for an ultrasonic sensor • Variation in the sound radiation pattern (beam angle) of both the ultrasonic transducer and the complete sensor system, and how this affects the maximum target distance and helps eliminate extraneous targets • Variation in the amplitude of the return echo as a function of the target distance, geometry, surface, and size, and how this affects the maximum target distance attainable with an ultrasonic sensor
Fundamental Ultrasonic PropertiesUltrasonic sound is a vibration at a frequency above the range of human hearing, usually >20 kHz. The microphones and loudspeakers used to receive and transmit the ultrasonic sound are called transducers. Most ultrasonic sensors use a single transducer to both transmit the sound pulse and receive the reflected echo, typically operating at frequencies between 40 kHz and 250 kHz. A variety of different types of transducers are used in these systems [4]. The following sections provide an overview of how the sound pulse is affected by some of the fundamental ultrasonic properties of the medium in which the sound travels.
Speed of Sound in Air As a Function of Temperature In an echo ranging system, the elapsed time between the emission of the ultrasonic pulse and its return to the receiver is measured. The range distance to the target is then computed using the speed of sound in the transmission medium, which is usually air. The accuracy of the target distance measurement is directly proportional to the accuracy of the speed of sound used in the calculation. The actual speed of sound is a function of both the composition and temperature of the medium through which the sound travels (see Figure 1).
Carlo Gavazzi’s UA Series ultrasonic sensors are designed for both distance measurement and object detection in tough environments. The range consists of both M18 and M30 housings. Discrete output types are available for presence and absence detection, and are ideally suited for detecting objects,such as transparent objects, that cannot be reliably detected by other sensors.Analogue output types are available on our sensors for applications requiring a measurement of the target object, such as detecting the level of fluid in a tank. The analogue models have your choice of 0-10 VDC or 4-20 mA outputs. Our more advanced ultrasonic sensor models incorporate teach functions, which allow the set-points to be configured with the push of a button, and via Windows-based software for applications where greater control of sensor parameters and variables is required. The Windows version also allows for settings to be saved and downloaded to multiple devices.
The Gavazzi UA 18 series self-contained multi function diffuse ultrasonic sensor with a sensing range of 60 to 3500 mm. 2 switching outputs - easily set up for 3 different switching modes and adjusted by teach-in - makes it ideal for level control tasks in a wide variety of vessels. A sturdy one-piece polyester housing provides the perfect packaging for the sophisticated microprocessor controlled and digitally filtered sensor electronics. Excellent EMC performance and precision are typical features of this sensor based on true distance measurement.
A self-contained multi function diffuse ultrasonic sensor with a sensing range of 600 to 6000 mm. The analog output is easily set up in 2 setpoints, pos./neg. slope and adjusted by teach-in -makes it ideal for level control tasks in a wide variety of vessels. A sturdy one-piece ABS housing provides the perfect packaging for the sophisticated microprocessor controlled and digitally filtered sensor electronics. Excellent EMC performance and precision are typical features of this sensor based on true distance measurement.
