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Monday, June 8, 2015

What is a laser distance meter

SUMMARY A Laser Distance Meter sends a pulse of laser light to the target and measures the time it takes for the reflection to return. For distances up to 30m, the accuracy is É3mm. On-board processing allows the device to add, subtract, calculate areas and volumes and to triangulate. You can measure distances at a distance. Compared with a good, old-fashioned tape there’s no contest. A Laser Distance Meter wins on every count: speed , accuracy, safety, versatility, convenience and functionality. Ultrasonic devices offer many of the same features but are less accurate.

Basic Principles A Laser Distance Meter* sends out a finely focussed pulse of light to the target and detects the reflection. The meter measures the time between those two events, and converts this to a distance. The formula is simple: Distance = Ä (Speed x Time). However the speed of light is 300,000 km per second, so to resolve differences of (say) 1 cm, the meter must measure time intervals of the order of billionths of a second. But don’t worry – the technology is well established and reliable! A laser distance meter can measure distances of up to 30m with an accuracy of É3mm. An Ultrasonic Distance Meter works on a similar principle, but instead of light it uses sound with a pitch too high for the human ear to hear. The speed of sound is only about ⅓ of a km per second, so the time measurement is easier, but there are other issues, as we shall see below. * Note that we are not looking at laser ‘range finders’ – these are much less accurate, and are typically used in golf, hunting and forestry.