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[FAQ] Ultrasonic Sensors

Ultrasonic sensing uses the propagating sound waves at a frequency above the range of human hearing (>20kHz) that can travel through a wide variety of mediums (air, fluid, or solid) to detect objects, measure distance, or track disturbances. Ultrasonic sensors can be used to detect a wide variety of materials regardless of shape, transparency, or color. For an overview on ultrasonic sensing fundamentals,company recommends you begin by reading the Ultrasonic Sensing Basics application note.company offers a variety of ultrasonic sensing ICs. The objective of this FAQ is to help recommend a specificcompany ultrasonic sensing device based on the application use-case and system requirements. Ultrasonic Sensing Application Measure Distance and Proximity Measure Level or Height of Liquid or Solid Measure Flow Rate and Direction of Liquid, Gas, or Heat Measure Concentration and Material Identification Object Tracking and Mapping Material Thickness and Flaw Detection Monitor Changes to Environment Description Use a single sensor to both generate and capture a round-trip time-of-flight echo to measure the distance between the sensor and the targeted object. Use a single sensor to both generate and capture a round-trip time-of-flight echo to measure the distance between the sensor and the targeted object. Use two sensors to capture the difference of transit time propagating in and against the flow direction as an independent upstream and downstream measurement. Use a single sensor to both generate and capture a round-trip time-of-flight echo to measure the changes in the speed of sound based on a fixed-known distance. Use at least two transducers with a fixed-known distance between on another. One transducer must always be used to generate and capture a round-trip time-of-flight echo, while the other transducers must only capture the round-trip time-of-flight echo. By comparing the resulting time of flight differences through triangulation. Use a single sensor to both generate and capture a round-trip time-of-flight to measure the thickness of a solid object, and determine if there are any voids within the solid. The transducer face must be made to couple to the solid material type for direct transducer to solid contact. Use two transducers, one to continuously generate the ultrasonic echo, and the other to continuously capture the difference in return echo zero-crossing frequency (Doppler shift).company Top Device Pick PGA460 TUSS4470 MSP430FR6047 TUSS4470 TUSS4470 TUSS4440 TUSS4470 Why Top Pick The PGA460 was designed specifically to measure distance using ultrasonic time-of-flight. The integrated driver, receiver, ADC, and digital signal processing logic simplifies the steps required to capture this time-of-flight data. The TUSS4470 supports the widest range of transducer frequencies from 30kHz to 1MHz to measure height from the top pointed down through air, or from the bottom pointed up through liquid. The customer organization MSP430FR604x and MSP430FR603x family of ultrasonic sensing and measurement SoCs are powerful, highly integrated microcontrollers (MCUs) that are optimized for water and heat meters. The TUSS4470 supports the widest range of transducer frequencies from 30kHz to 1MHz to properly couple the transducer and enable this measurement through nearly all gases, liquids, or solids. Multiple TUSS4470 devices can be easily synchronized due to the device’s ability to independently enable the receiver path regardless of the driver block’s state. This means the start of the pulse generation can be used as the sole time-of-flight origin reference for all devices. To propagate sound waves through a solid, a large amount of sound pressure must be generated by using a transformer driver. The TUSS4440 is able to generate hundreds of volts to excite transducer, while normalizing the time-of-flight echo response regardless of the flaw dimensions. The TUSS4470’s built-in zero-crossing feature allows the receiver to continuously monitor the incoming echo frequency. If the object is approaching the sensor, the zero-crossing frequency will increase, while an object leaving will cause the zero-crossing frequency to decease. Recommended Evaluation Tool BOOSTXL-PGA460 BOOSTXL-TUSS4470 EVM430-FR6047 BOOSTXL-TUSS4470 BOOSTXL-TUSS4470 BOOSTXL-TUSS4440 BOOSTXL-TUSS4470 Notes Enable near 0mm detection by using a bi-static transducer pair for a separate transducer to generate the echo, and another transducer to capture the round-trip time-of-flight. For top-down level sensing, use lower frequency transducers. For bottom-up level sensing, use higher frequency transducers.company no longer recommends using the TDC1000 for flow rate application due to known stability and accuracy issues of the device’s STOP pulse generation. Enable one-way measurements by using a bi-static transducer pair facing each other for a separate transducer to generate the echo, and another transducer to capture the one-way time-of-flight As transducers are added to the receiver array, the accuracy and addition details of the object to be tracked or mapped are increased. It is important to use a contact transducer acoustic matched to the solid you are measuring the thickness of. Improper transducer face type or poor mounting will result in invalid results. Monitoring the Doppler shift of the return echo is one method of seeking changes to the environment. Capturing the echo envelope over time per time-of-flight measurement is another way to monitor environmental changes by comparing the latest record cycle to the previous record cycle.company Ultrasonic Sensing IC Device Comparison: TUSS4470 TUSS4440 PGA460 MSP430FR6047 TDC1011 / TDC1000 Device type Analog front-end Analog front-end Analog front-end + digital signal processor (integrated) Analog front-end + digital signal processor (integrated) Analog front-end Supported transducer frequencies 40 kHz – 1 MHz 40 – 440 kHz (pre-drive) 40 – 500 kHz 30 – 80 kHz & 180 – 480 kHz 50 kHz – 2.5 MHz 31.25 kHz – 4 MHz Channel count 1 Channel 1 Channel 1 Channel 2 Channel TDC1011: 1 Channel TDC1000: 2 Channel Drive topology - Direct drive (max 36 V) - Pre-drive Transformer drive - Transformer drive - Direct drive with added FETs Direct drive (max 3.3V) Direct drive (max 5V) Gain stage 86 dB logarithmic amplifier 86 dB logarithmic amplifier 6 point time-varying gain (32 to 90 dB) Fixed gain (6.5 to 30.8 dB) Fixed gain (20 to 41 dB) Outputs - Analog echo envelope - Zero crossing - Envelope threshold detect - Analog echo envelope - Zero crossing - Envelope threshold detect - DSP processed output (time-of-flight, amplitude, width) - Echo data dump (down-sampled echo envelope) - Raw digital data path (ADC, bandpass filter, rectifier, lowpass filter) - Flow rate - DSP processed output (time-of-flight) - Zero crossing - Echo start and stop pulse Temperature sensor No No On-chip temperature sensor On-chip temperature sensor Interface to RTD Diagnostics SPI diagnostics SPI diagnostics - System diagnostics (frequency, decay, excitation voltage) - Supply diagnostics (overvoltage) Programmable None Automotive qualified device N/A N/A PGA460-Q1 N/A TDC1011-Q1 TDC1000-Q1 Output interface - SPI for programming - Analog output - SPI for programming - Analog output - USART (UART + SPI) - OWU - TCI - UART - I2C - SPI SPI The following collateral will be available on E2E until officially released to the product page: TUSS44x0 E2E Content: BOOST-TUSS44x0 EVM-GUI Overview and Quick Start Video: Ultrasonic FAQ Archives: PGA460: <secret URL>/support/sensors/f/1023/t/640810 TDC1000: <secret URL>/support/sensors/f/1023/t/724028 TDC1000 no longer recommended for accurate flow metering. Please consider using the TUSS4470 as an alternative to the TDC1000 for all ultrasonic applications.

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