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Laser rangefinder questions we actually get
Eight questions that decide whether a module fits, answered without marketing padding. If your question is not here, write it to tommy@erdimail.com and it gets answered, and probably added.
Which wavelength should I choose, 905 nm or 1535 nm?
905 nm parts are smaller, cheaper and faster (kilohertz rates), and they are limited by eye safety to low pulse energy, which caps usable range and hurts performance in haze. 1535 nm sits in a band the cornea does not focus onto the retina, so far more pulse energy is available at a stated Class 1 module level: that is how 6–23 km modules exist at 200–400 g. If your requirement is past roughly 3 km, 1535 nm is the practical choice; below 1 km, 905 nm usually wins on cost, size and rate.
Is a 1535 nm module automatically eye-safe?
No. The module document may state Class 1, but the classification that matters is the one for the assembled product — aperture, collimation and any additional optics change the accessible emission. Treat the module statement as an input to your own assessment, not as a conclusion about your device.
Why do the published ranges differ so much between similar models?
Because they are measured against different targets in different weather. The same 1535 nm module family quotes 6,500 m against a 5 × 15 m target and 12,000 m against a 20 × 20 m diffuse target at 30 % reflectance. Compare the test condition, not the headline number.
What does the accuracy figure include?
Usually the module's own ranging error under its test conditions, not your installation error. Where the manufacturer gives a proportional term (for example ±0.3 m + D × 0.7 ‰), the error grows with distance and the scalar figure we list is only the near-field term. The raw string ships in the dataset for exactly this reason.
Which interfaces are available?
UART/TTL at 3.3 V is the most common on 905 nm modules; 1535 nm long-range modules mostly use RS-422, which survives longer cable runs and noisy vehicle supplies. Some models add RS-232, CAN or a discrete trigger. Check the model page before designing the harness.
Do you publish prices?
No. Price depends on quantity, configuration, export paperwork and whether you need a custom harness or firmware option. Ask for a quote with target, range and quantity and you get a number for your configuration.
Can I get a sample before committing to a build?
Yes — say so in the first email, with the interface and mounting you intend to use. Sample lead time and terms are quoted per model.
Where do these specifications come from?
From the manufacturer's published model pages and module documents, transcribed and cross-checked, with the test conditions kept verbatim. Every row links to its source page. Where a figure is ambiguous we say so rather than smoothing it over.