1535 nm Rangefinder Modules: Mass Budget for Gimbals

Choose a 1535 nm rangefinder module for a gimbal by its installed mass and balance envelope, not by its headline range. Start with the mass of the supplied module, then add the cable, connector, bracket, fasteners, protective parts, and the distance of their combined centre of gravity from the gimbal axis. A module can fit the payload limit yet still leave the gimbal poorly balanced if its installed centre of gravity is too far forward or aft.

This is an installed-mass method, not a specification for a 1535 nm product. Current 905 nm records provide two useful numeric baselines: the LR1000E2 is listed at ≤ 10 g, while the LRF3000A1 is listed at 12 ± 0.5 g. Those published module-only rows do not state that they include a cable, connector, bracket, or fasteners. Keep those items as separate weighed entries until the supplied assembly is known.

Manufacturers often quote mass for the module alone, while the gimbal sees the module plus everything needed to install it and route its cable. The two can differ enough to change whether the payload fits at all, or whether the gimbal can hold position and return to its commanded attitude without fighting an offset centre of gravity.

Start with published module mass, then add the integration mass

A data-sheet mass is a starting point rather than the final gimbal payload figure. For example, the LR1000E2 record lists dimensions of 25.65 × 13.2 × 24.6 mm and a weight of ≤ 10 g. The LRF3000A1 record lists dimensions of 13.5 × 25.1 × 27.8 mm and a weight of 12 ± 0.5 g. The two records are 905 nm examples only; they do not establish the size or mass of any 1535 nm module.

Use the current model record for the exact module selected. The 1535 nm rangefinder module overview is a useful starting point for the application discussion, but it does not replace a delivered-unit mass record or a physical weigh-in. If the supplier record does not state whether an accessory is included, do not subtract it from the payload budget.

Turn mass and offset into a balance calculation

For an initial static balance review, calculate the moment about each relevant gimbal axis:

Moment = mass × perpendicular offset from the axis.

Use one consistent unit set, such as g·mm, for every item. The calculation is a comparison tool: it shows how a small mass becomes significant when its centre of gravity is far from the axis. It is not a motor-torque rating, because the gimbal manufacturer must provide the allowable static and dynamic load, travel range, and control limits.

Start with a published mass row such as the LR1000E2 or LRF3000A1 examples, then replace the module term with the measured mass and measured centre-of-gravity offset of the actual delivered unit. The sum is the static installed moment for that one assembly, not a motor-torque rating and not a claim about any 1535 nm module.

Repeat the calculation for pitch, roll, and yaw where the mechanical arrangement makes an item offset from that axis. A payload may look balanced in one parked orientation but move its effective offset as the gimbal rotates. Check the actual travel range, not just the forward-looking position.

Cable and connector mass belong in the mass budget

Cables matter twice: they add mass, and their routing can apply a restoring force or drag that changes with gimbal angle. A cable tied to the airframe too tightly can make a carefully balanced static assembly behave differently in motion. Conversely, an unsupported cable loop can shift or contact the structure during travel.

Make cable entries traceable. Record the actual cut length, connector shells, strain relief, clips, service loop, and any protective sleeve. Weigh the fully prepared harness rather than estimating from a wire catalogue. Then mount it using the intended routing before locating the centre of gravity. A bare-module result is useful for screening, but it is not an installation acceptance result.

• Measure the supplied module or assembly on a scale with suitable resolution.
• Weigh the completed cable and connector assembly separately before installation.
• Weigh the bracket, fasteners, adapters, and protective parts as fitted.
• Record each item’s centre-of-gravity offset from every relevant axis.
• Calculate each moment and sum the signed contributions by axis.
• Compare the installed mass and balance result with the gimbal maker’s documented limits.
• Move the gimbal through its intended travel and check for cable tension, contact, and change in balance.
• Re-weigh and re-check after any cable-length, bracket, or enclosure change.

Use range and mass as separate decisions

Range is not a proxy for installed mass, and a lower mass does not automatically produce the better payload. The LR1000E2 and LRF3000A1 records illustrate why separate columns help: one lists ≤ 10 g and the other 12 ± 0.5 g, while their published measuring and operating conditions differ. For the LRF3000A1, the ≥ 3,000 m maximum-ranging row is explicitly conditioned on a 70% reflectivity building target, clear weather, and visibility of at least 4 km. That range condition should not be used to infer balance, and the mass row should not be used to infer installed cable mass.

For a 1535 nm project, request the supplier’s applicable delivered-configuration documentation, then run the same installed-mass worksheet. Preserve missing fields as missing. A planned range, wavelength, or product photograph cannot establish the mass of a module, its harness, or its centre of gravity.

A weigh-in acceptance record for gimbal integration

A practical acceptance record should allow another engineer to reproduce the decision. List the module identifier and revision, the scale resolution, every mounted item, the cable routing, the gimbal axes, the measured offsets, and the configuration used during the travel check. Attach photographs of the completed assembly only as configuration evidence; the values should come from the scale and the measured geometry.

Keep the supplier’s quoted mass separate from the measured installed mass. If the two differ, identify whether the difference is due to accessories, a revision, a protective part, or a measurement method before changing the payload limit. That distinction is especially important when a gimbal is near its allowable mass or balance boundary.

For model-reference details, see the LR1000E2 and LRF3000A1 pages. For a proposed integration, provide the intended module configuration, completed mass worksheet, axis offsets, cable routing, and gimbal limits through the contact page so the documentation can be reviewed against the actual assembly.

FAQ

Category pages: Long range laser sensor · Laser rangefinder module

Models mentioned in this article

• LRF3000A1905 nm · up to 3 km · UART · TTL · 12 ± 0.5 g
  From $180 · shipping includedSee price & buy
• LR1000E2905 nm · up to 1 km · UART · TTL · ≤10 g
  From $60 · shipping includedSee price & buy