Utilization of ppm in Measurement
1mm+1ppm is the abbreviation of 1mm+1ppm×D (kilometer), which reflects the nominal ranging accuracy of the total station or rangefinder.
Among them: 1mm represents the fixed error of the instrument, which is mainly caused by the measurement error, centering error, and phase measurement error of the instrument plus constant. The fixed error has nothing to do with the measured distance. That is, no matter how far the measured actual distance is, the total station will have a fixed error not greater than this value.
1ppm×Dkm represents the proportional error, where 1 is the proportional error coefficient, which is mainly caused by the instrument frequency error and the atmospheric refractive index error. ppm means parts per million (a few), and D is the distance value actually measured by the total station or rangefinder, in kilometers. As the actual measurement distance changes, the proportional error part of the instrument also changes proportionally. For example, when the distance is 1 km, the scale error is 1 mm.
For a total station or rangefinder with a ranging accuracy of 1mm+1ppm, when the measured distance is 1km, the ranging accuracy of the instrument is 1mm+1ppm×1(km)=2mm, that is to say, the total The distance of the station instrument is 1 km, and the maximum ranging error is not more than 2mm.
3 seconds is the time for ranging
Selection Guide for Laser Range Finders
1. Measuring range
2. Measurement accuracy
3. Where to use
Basically divided into the following situations:
a) It only needs to measure the distance within a few meters or a dozen meters,
And when the accuracy requirement is not high. Suggestion - "ultrasonic range finder" can be selected.
Remarks——The measurement effect of the ultrasonic rangefinder is greatly affected by the environment, and its stability and directionality are worse than that of the laser rangefinder, but the price is relatively cheap, and it is suitable for indoor measurement.
b) The measurement distance is not long, and it is mostly used indoors, requiring high precision.
Suggestion - You can choose "handheld laser rangefinder as shown in the left picture".
Remarks——The handheld laser rangefinder is suitable for indoor use, and the measurement accuracy and effect are very good. When measuring outdoors, due to the influence of outdoor light pollution, the accuracy of the handheld laser rangefinder drops significantly.
(If the user needs to detect in an outdoor environment, it is recommended to use a laser sight and a reflector in combination to achieve the expected range and effect.)
Note: The continuous output laser used by the laser rangefinder is visually in the red spectrum range. When the eyes look directly at it, it may cause irreversible damage to the eyes.
c) The measurement distance is relatively long, and it is mostly used for outdoor use.
Suggestion - buy "telescopic laser rangefinder" (ie: laser rangefinder telescope).
