Hi,
Im needing some guidance on where I can use LightWare LiDAR (175-LW20/C) to measure cables and other overhead obsticles at driving speeds 55mph or above. Would this be a good start?
Hello Jsmembreno,
175-LW20/C has IP67 environmental protection rating which makes this resistant to dust and water. Making this suitable for external mounting. The measuring range is .2 to 100meters (.6 to 328ft). As to where to test this would be up to you as the user.
Some additional context on the design objectives would be helpful.
The device operates on the principle of measuring the amount of time required for a pulse of transmitted light to be reflected and received back at the sensor. In order to be detected, objects have to reflect enough light for the sensor to get a measurement.
The device specifications reference a target size of 0.9x0.9 meters, to a maximum distance of 100m.
A flat surface 3 feet square is a relatively large target, though it appears smaller at greater distances. A “cable” by contrast might only be an inch in diameter and have a circular cross section, resulting in a great deal less light being reflected back at the sensor than an equivalent flat surface. Whether or not the objects you would wish to detect reflect enough light at the distances in question for the sensor to notice would be a major consideration.
Another question is whether the geometries of the situation work. The transmitted light pulse has a beam divergence of half a degree or less:
This is akin to viewing the world through a drinking straw. If traveling at a high speed past a stationary object, the length of time during which the object would be visible through that straw is quite short.
Hi Rick,
Thanks for the feedback. Essentially what I want to create is a digital height pole to measure overhead utility cables and bridges. The max height for the cables would be 75ft. Those being high voltage cables everything else is usually under 32ft.
Similar to below:
https://www.acuitylaser.com/laser-sensors/case-studies/ar2500-laser-sensor/laser-height-pole-measurement/
That press release mentions a sampling rate of 30 kHz, which is 6x faster than the 175-LW20/C is capable of. This would have bearing on the geometry issue mentioned above.
It also mentions an “AR2500” laser measurement unit, for which I’m not finding specifications listed. The “AR2700” unit would seem to have a somewhat tighter beam focus, and mentions a somewhat shorter range to a less-reflective target. This complicates any direct comparison of receiver sensitivity between the two, and neither is a very good proxy for your use case involving smaller targets at shorter distances.
At 55 mph and the maximum 5 kHz sample rate of the sensor in question, the field of view would move about a fifth of an inch between samples. That’s perhaps near the low end of what would be feasible for the application in question, but if it’s enough, it’s enough.
I can’t say that this sensor will suit your needs, but also don’t have good reason to say you shouldn’t waste your time evaluating it. Just be mindful that a failure would mean not seeing a cable or some similar obstruction, and if methods aren’t in place to detect such events if/when thy occur, the results could be quite unpleasant.
Thanks again, Im looking into the SF30-D sensor.
https://www.digikey.com/en/products/detail/lightware-lidar-inc/SF30-D/15848663