Rangefinder Range vs Rate: Compare Echo Conditions

A useful laser rangefinder range update rate comparison starts with a particular surface, distance and operating environment—not with the largest number in each catalogue row. A module may detect a target yet return readings too slowly for the host, or report frequently while its distance error exceeds the application’s tolerance. Those are separate acceptance questions.

Direct time of flight (dToF) describes measuring distance from the travel time of light. Pulsed time of flight is an implementation within that approach, not an opposing sensing principle. The practical comparison is the documented operating point and the performance verified on the intended target.

Why catalogue rows are not simultaneous guarantees

A range row describes a distance under stated target conditions. An accuracy row describes a measurement tolerance under its own stated terms. A frequency row describes measurement frequency, which may depend on configuration or the returned signal. Unless the source explicitly connects these conditions, taking the most favourable value from each row does not establish that all three occur together in an installation.

For example, LRF50H lists a selectable frequency range, while LRF1500H automatically switches between two frequencies according to echo strength. Neither fact alone establishes the valid-reading cadence at the farthest listed distance on a particular surface. A comparison must follow the output all the way to the host, where missing readings and processing delays can matter.

Keep the measurement frequency separate from the valid-reading rate: the latter is the number of readings accepted by the application’s defined validity rules per unit time. It is an acceptance result, not a published specification inferred from a frequency row. Also record the longest gap between valid readings; an average can conceal a pause that matters to a controller.

Conditioned range and update rate

Both product records describe direct time-of-flight modules. The LRF50H record specifies 0.05–50 m at 90% reflectivity and 0.05–15 m at 10% reflectivity. Its frequency is 20 Hz–10 kHz, with a 1 kHz default. Its accuracy is ±5 cm below 10 m and 1% at or above 10 m, at 2σ.

The LRF1500H record specifies 0.05–1,500 m at 90% reflectivity and 0.05–300 m at 10% reflectivity. Its frequency switches automatically between 1 kHz and 50 Hz according to reflected-signal intensity. Its accuracy is listed as ±10 cm below 10 m and 1% at or above 10 m; the record does not state a statistical qualifier for that accuracy row.

These figures are source specifications, not proof that a particular target meets them at a particular rate. Reflectivity alone is not a complete description of the return: target size, orientation, background, ambient light and the installed optical path should be recorded as well. Do not assign a frequency to a reflectivity or distance merely because both appear in the same product record.

The specified operating temperature is −20 to +60 °C for both models; the LRF50H record additionally specifies non-condensing conditions. Temperature bounds are not evidence of simultaneous maximum range, accuracy and frequency throughout that interval. Establish the intended operating conditions and the acceptance results together.

A requirements comparison table

Use each row as a separate gate. The model entries are source figures; the final column describes what the application must establish, not a promised result.

Do not rank the accuracy rows by the short-distance figures alone. They have different stated statistical detail, and the application may operate on the other side of the distance boundary. The project should define the reference, sample treatment and pass limit before collecting readings, rather than choosing a favourable interpretation afterwards.

Acceptance criteria for the intended target

Create one test record per combination of target, distance and environment. Use the same reference and validity definition for each candidate; note any differences in installation or configuration. The following checklist turns a catalogue comparison into a repeatable decision.

1. Describe the scene. Record target material or measured reflectivity, dimensions, orientation, distance and surrounding surfaces. If reflectivity is unknown, identify the actual sample rather than assigning it a percentage by appearance.
2. Set the installation. Record mounting, alignment, any protective window, ambient light, temperature and condensation status. Test the installed optical path rather than assuming a bare module represents the finished assembly.
3. Define the result. Before the run, set the acceptable distance error, valid-reading fraction, minimum valid-reading rate, maximum gap and observation duration. Define how invalid readings and reference uncertainty are treated.
4. Capture timing and distance. Log timestamps, reported distance, validity status and the reference distance. Record configured frequency where applicable, along with target and environmental conditions. Use a consistent clock and note where in the host chain timestamps are taken.
5. Review transitions. For the adaptive model, identify changes in observed inter-reading intervals and retain the surrounding records. The record associates frequency selection with echo strength; it does not provide a transition threshold to assume. Do not infer internal echo intensity from timing alone.
6. Decide per condition. Calculate error against the reference, valid-reading fraction, valid readings per second and longest gap. Mark each requirement pass, fail or not established. A pass in one scene does not establish a pass in another.

For a moving host, choose the maximum acceptable gap from the application rather than simply requiring a high average rate. Check timestamps after any buffering and filtering used in the actual system. A faster measurement setting cannot by itself prove that a host receives timely, usable readings.

Compare candidates using the same observation window and acceptance definitions, but record their actual configurations separately. A useful results sheet lists the number of received readings, the number accepted, the resulting fraction, the accepted readings per second and the longest interval between accepted readings. Keep the raw timestamps as well as the summary, so that a later review can distinguish a sustained reduction in cadence from a short interruption. State whether the observation window includes startup and whether the reference remains stable throughout the run. If a condition cannot be reproduced or a validity rule remains unresolved, mark that result as not established rather than treating missing evidence as a pass.

For integration context, see the 905 nm UART module guide. The LRF1500H source also contains unresolved inconsistencies in its out-of-range representation and checksum example; obtain clarification for the applicable unit before defining validity or decoding rules. Neither discrepancy should be resolved by assuming a value from another model. Share the target conditions and acceptance limits through the contact page.

FAQ

Category pages: ToF distance sensor · Laser rangefinder module

Models mentioned in this article

• LRF50H905 nm · up to 50 m · UART · 15 ± 2 g
  From $80 · shipping includedSee price & buy
• LRF1500H905 nm · up to 1.5 km · UART · I2C · 20 ± 2 g
  From $250 · shipping includedSee price & buy