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| Max range | All Laseroptronix laser distancemeters are specified to a gray 10% reflective target. The max range is defined as a safe measurement in good environment. The 10% reflectivity is measured at the vawelength of the laser which is Infrared in most cases. The eye can see the gray scale very different so the eyes are no good detector to guess reflectivity of targets. We have many years experience in thiese problems and can help you to select the best solution without getting trouble. |
| Clear and clean air. | Max range depends a lot on application and environment in the measurement zone. Laseroptronix do normally specify the range as the max range for a safe and accurate detection in clear air and to a gray 10% reflective target.
This factor is important and at long range it often sets the limit of max detectable range. Fog and mist reduce the range a lot as it absorbs the light energy and gives less photons reflected back to the detector. Small particles scatter the light in all directions. This makes losses in the transmitted energy from the laser. Fog have plenty of small water drops and they scatter light. DME 300 from Laseroptronix do loose range if the density is high and if it is higher than so it starts to measure at the particles and output signal is a wobbling distance reading and typically 20 - 50 meter distance. DME 1000 is better as it is more powerful but still the problem is there. DME 10 000 is the best and as it have a very high peak energy is can filter better by the amplitude. Range is still lost |
| Rule of thumb for clear and clean air measurements | If you can see target you can measure. If the target is hidden and not visible you will not have good readings and no measurements. If you want to measure to non visible targets Pls phone us for a discussion. It can be possible but need a lot of analyze. |
| Obstacles in the air. | Snow and heavy rain block the light and each object gives a reflex which can be so strong that it gives a measurement. This can be handled in the electronics in many ways. This problem increases the complexity of the laser distance meter.
DME 400 which is our cheapest distance meter is not so good when there are to large objects in the air like heavy snow. Normal rain and light snow does not disturb measurements. DME 1000 will soon have a last pulse logic which filters away the closest reflexes and search for last reflex equal to target. DME 10 000 have a last pulse logic which can be set and controlled. This system works if you can see target with your eyes. If you can not see target you can not measure anyway so it does not matter. |
| Reflectivity of the target. | This factor is very important. If target is white or mat black it have a large impact on the max range the instrument can get. The 10% we normally use is relatively dark by the eyes but as the distancemeters often have IR light the gray scale for the eyes is very different compared for the monochromatic IR light most distance meters uses. Check this as this can fool anyone a lot.
10% reflective targets = specified max distance range. 100 % reflective targets = mat white gives over the doubled range of the distance meter. Reflex tape is better than 100% and can 3-10 double the range. 4% reflective targets is carbon black and it reduces the range with over 50% compared to the 10% reflectivity. 1% reflective targets exist on some special plastics like radomes of airplanes. They reduce the max range a lot. |
| Split reflexes and angled surfaces | This is a typical practical problem. If you measure to a tree the reflexes are spread out in depth and the reflex becomes less sharp. Trees in winter time without any leaves are hard targets to measure.This gives lost range.
If you measure to a surface in a flat angle the laser beam is spread out in distance a lot. A 50 cm laser beam at 5 degree angle becommes very long in the distance measured angle and if so where do you measure ? |
| Accuracy | This point is not so easy. Laseroptronix do always count worst case for accuracy.
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| Noise in readings | Single shot systems make an internal average in some cases and we display the sum of all of them. DME 300 as an example makes 60-200 measurements which are filtered and then averaged. This gives a real accuracy of less 1 meter in worst case.Internally the system have about 20 cm recitability. This is increased by factor 5 to get a correct accuracy value. All sensors have unique characteristics.
DME 10000 use a single shot and calculate to this single shot. This gives an honest 5 meter accuracy. This system can read to several reflexes and this is set by the operator. The profilometer with very high output rate have a very complicated electronics and each shot is accurate to less 10 cm at the full 25000 Hz rate. Under good circumstances this system can measure down to the 1 cm accuracy area. |
| Thermal drifts | This is always present and makes reduced accuracy. The distance meters are compensated as good as possible . Good stability in ambient temperature is always preferred. |
| Laser safety problems | Most of our systems are classified to class 1 measured to the way specified in IEC 825-1 regulations. The lasers do normally measure at a vawelength in near IR area. Most common is 904 nm and this is not visible by the eye. The pulse energy is high but pulses are very short ( down to 6 nsec) so energy becomes low in each pulse. The energy is so low that it can dot burn the eye and therefore it is harmless for the eye.DME 300 have about 15 W in peak power but average power is very low.
The DME 10000 have a high and powerful energy level but it is working at 1,54 micron vawelength. At this area the eye is not transparent and the energy stops at the surface of the eye. Here it is converted to heat but the total amount of heat is anyway so low that it is harmless for the eye. If vawelength should have been shorter than 1,5 micron this should have been a dangerous class 4 laser system. The profilometer is scanned and therefore the beam is moving. The laser have a class 3B safety level when the beam is not scanned . The scanner spread out energy so the complete system is a class 1 system when used in its application. |
| Lifetime and maintenance | The only part in a distance meter which is degradated by the time is the laser diode or laser source. Almost all of our systems have a laser diode as light source. They have a good reliability and life time. Typically they work for 20 000 to 50 000 hours with no service at all.
DME 10 000 have a lamp system where lamp needs replacement now and then. When this system is used in its normal applications the service is very rare and not done each year. |
| LaseroptronixAB |
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Telephone 46-70 714 04 70
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| Enhagsslingan 23 |
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| 187 40 Täby |
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Säte i Täby Kommun Glimmervägen 8 187 34 Täby / Sweden |
| Sweden North Europe |
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Created 2005-10-27 by Allan Jansson
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