Electricity + Control September 2019

SENSORS, SWITCHES + TRANSDUCERS

Ultrasonic sensors at work in challenging applications Demand is growing globally for accurate and cost-effective distance measurement capabilities in a wide range of industrial, public sector and research applications. According to research by Research and Markets, ultrasonic sensors have the edge in helping organisations meet their distance measurement requirements.

Take Note! With advances in pro- grammability, smart ultrasonic sensors are providing an accurate, rugged and cost effective distance measurement solution for a wider range of applications. Ultrasonic sensors are ideal for measuring the height and level of liquids and solids, measuring the location or size of an object, and detecting the presence of people or objects.

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U ltrasonic sensors offer a number of advantages for measuring distance in challenging applications. First, non-contact sensors have inherent advantages over contact measurement approaches. They work better in environments where corrosive or dirty materials are likely to impact negatively on the performance and maintenance costs of contact sensors. Non- contact sensors also work better in applications where it is critical that the material or object being measured is not corrupted or damaged by direct contact with a measurement device. In addition, ultrasonic sensors are simpler to operate, more rugged, require less maintenance, and often cost less than other non-contact sensor technologies. They outperform the alternatives in many applications because their operation is not sensitive to ambient light levels, the colour of the target, or the target’s optical transparency or reflectivity. With advances in programmability, smart ultrasonic sensors are providing an accurate, rugged and cost effective distance measurement solution for a wider range of applications. This Senix Sensor Insights tech brief presents some common strategies and techniques for getting the most value from ultrasonic sensors in various applications. The intention is to help users leverage low-cost ultrasonic sensors broadly and successfully. How ultrasonic sensors work Ultrasonic sensors are ideal for measuring the height and level of liquids and solids, measuring the location or size of an object, and detecting the presence of people or objects. In measuring distances, they use ultrasonic transducers to create and send a sound pulse – above the range of human hearing – towards the intended target. The sensor detects the return

echo and determines the distance of the object from the transducer element based on the time of flight. (Figure 1.)

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Figure 1.

Addressing variables in challenging environments There are a number of proven techniques for configuring ultrasonic sensors to address challenging applications. Some of the main application challenges faced and the ways in which ultrasonic sensors can be configured to mitigate these challenges are outlined below. Turbidity or obstacles in tanks In liquid level applications, turbulence of the material or the movement of stirrers or other

objects within the signal path can interfere with measurements. (Figure 2.) New generation smart ultrasonic sensors have signal filtering and processing capabilities that allow users to ignore measurements

Figure 2.

triggered by turbulence or non-target moving objects. Sensors can be configured to reject certain measurements, average a series of measurements, or limit the rate at which the output changes. A running average of readings will smooth the output to give an accurate measurement of tank levels. Input filters can be used to accept only the maximum or minimum readings in a sample to negate the effect of waves or non-target objects.

36 Electricity + Control

SEPTEMBER 2019