Level measurement is a ranging problem in disguise
A silo, a tank, a hopper or a bunker stores material, and the thing you want to know is how much room is left. A downward-facing laser distance sensor measures exactly that: the distance from the sensor to the surface of the contents. Subtract it from the known geometry and you have a level.
What makes the application hard is not the distance. It is the surface. Grain forms an angle of repose and the beam hits the slope, not the average level. Cement dust hangs in the air and scatters the pulse. An agitator passes through the beam twice a minute. Foam absorbs. A shiny liquid reflects the pulse away at anything other than a perpendicular angle.
Modules used for level and fill measurement
| Model | Published range | Price | Where it fits |
|---|---|---|---|
| LRF50H | 0.05–50 m at 90% reflectivity; 0.05–15 m at 10% | $160 | Small bins and hoppers, short throw |
| LRF100H | 0.05–100 m at 90%; 0.05–30 m at 10% | $230 | Medium silos, 9–36 V DC supply |
| LRF200H | 0.05–200 m at 90%; 0.05–70 m at 10% | $250 | Tall silos and long bunkers |
| LRF300H | 0.05–300 m at 90%; 0.05–100 m at 10% | $280 | Very tall storage, stockpile profiling |
| LRF600H | 0.05–600 m at 90%; 0.05–200 m at 10% | $350 | Open stockpiles and long-range yard measurement |
| LRF10VB | 0.05–9 m at 90%; 0.05–5 m at 10% | $80 | Small vessels and dose hoppers |
The two figures per model are the whole argument for reading a datasheet properly. Inside a silo the surface is often dark, dusty and angled — the 10% column is the realistic one, and it is a third of the headline number.
Five installation decisions that decide the result
- Where the beam lands. On a cone of grain, a single point reads the slope. If you need an average you need several sensors or a scanning device — a single-point module tells the truth about one spot only.
- The blind zone under the sensor. Every module has a minimum range. When the silo is full, the surface is inside that zone and the sensor reports nothing. Mount the sensor high enough that full is still outside the blind zone, or accept an “unknown when full” state in the software.
- Dust on the window. In a cement or flour environment the window is the lifecycle part. A window that fails its acceptance test is a level system that reads short. See protective window acceptance.
- Moving parts in the beam. An agitator arm crossing the beam produces a plausible-looking false level. Filtering by expected change rate, and rejecting readings that return during a known agitator window, is cheaper than a better sensor.
- Material transparency. Clear liquids and clean glass are the classic failure case for laser level sensing. Confirm with a sample before specifying.
Where an ultrasonic or radar sensor wins
If the vessel is full of fine powder that stays airborne, or the surface is foam, a non-optical technology is often the better choice, and saying so costs less than a failed installation. A laser module is at its best on a clear sight line to a defined surface: grain, aggregate, ore, packaged goods, and liquids that are not mirror-smooth.
Next step
Send the vessel height, the material, the dust level and the mounting position to tommy@erdimail.com. Background reading: the level and AGV sensing checklist.
Where two source documents for a model conflict, the model page states the conflict rather than choosing one value, and the current datasheet governs the order.