BY ZOHER FATAKDAWALA Bosch Power Tools & Accessories
The Accuracy of Laser Measurement Devices
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ranslating an architect’s thoughts, designs, and calculations into real-world edifices requires accurate measurements of everything on the job sites. That means what is used to measure must be accurate and conform to standards for every use. While sometimes little notches in wood or metal are used to measure inches and feet, like a ruler or tape measure, today’s advanced devices that can use sound and light to measure an entire project in mere minutes. It goes unsaid that accuracy is extremely important. With flatwork for instance, accurately measuring the length, width, depth, and slope are all critical factors that mean the difference between success and abject failure. Inaccurate measurements bring issues from puddles due to poor drainage to unwanted cracks and instability, which can undermine the integrity of the building. The question is, how can a tradesperson ensure the measuring tools they use on the jobsite are accurate and will perform appropriately in varying conditions? When it comes to measuring, three of the most widely used tools are the traditional metal tape measures, sonic wave generators and laser range finders. STEEL TAPE MEASURES The National Institute of Standards and Technology (NIST) has an underground facility staffed by professional metrologists—scientists that study and practice the science of measurement. This intrepid group calibrates master tape measures for athletic organizations, crime scene investigators and others. They employ a number of techniques to ensure that tape measures are accurate. For instance, a tape measure that is 60 meters (about 197 ft.) can be confirmed
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within 0.1 mm, or the thickness of a piece of paper. The reason why tape measures are on pretty much every tool belt around the world is they work, are inexpensive and can handle most of what is thrown at them. The challenge with tape measures is that several factors can impact their accuracy—or lack thereof. For instance, because they are usually steel they are subject to thermal expansion, which is the tendency of matter to change its shape, area, volume and density in response to a change in temperature. In other words, temperature can make
“With flatwork…
accurately measuring the length, width, depth, and slope are all critical factors that mean the difference between success and abject failure.
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them shrink or expand depending on how hot or cold the environment is at the jobsite. Steel tapes are calibrated to have the optimum measurement at 68° F (20° C). On a hot summer day where the temperature can get over 100° F (38° C), they can be off by enough to require correction. Common steel tapes have a coefficient of thermal expansion about 0.000,011,6 units per unit length per degree Celsius change. This means that the tape changes length by 1.16 mm per 10 m with every 10° C change from the standard temperature. For a 30-m long tape with standard temperature of 68° F, at 104° F, the change in length is 7 mm over the length of the tape.
ELECTRONIC MEASURING The digital revolution has brought some new technology that has been gamechangers when it comes to the speed and accuracy of taking measurements anytime, anywhere. Manual range finders or distance measuring tools are handheld, lightweight, and batterypowered, which allows for several hours of regular use each day. They usually come in two categories, electromagnetic distance measurement (laser) or ultrasonic (sound). These operate in similar ways but deliver quite different results. They work by sending out light or sound to an object they want to measure then the signal reflects off that surface and returns to the rangefinder where the device instantly calculates the distance. Ultrasonic devices can measure the distance of objects regardless of shape, color, or surface texture and they can also measure moving objects. They can be used without needing to touch an object, which helps in wet concrete scenarios. At retail, they usually cost less than laser rangefinders but come with two massive disadvantages, they have significant range limitations and are notoriously inaccurate. Errors are caused by the sound reflecting random items close to where they are pointing, instead of the desired target. Because of this, ultrasonic devices work best on clean surfaces in empty rooms. LASER RANGEFINDERS Today’s digital laser distance measuring tools have been designed for functionality, usability, and accuracy. Besides the fact that they can be operated by a single person, they are also much less susceptible to user errors such as incorrect positioning. What’s more, is some rangefinders come
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2/16/22 9:06 AM
