LM-1030 Online Digital Diameter Gauge: Specifications and Where the Limits Are

An online digital diameter gauge measures the outer diameter of a moving product without touching it, continuously, at production speed. The POMEAS LM-1030 does this by projecting green LED light past the product onto a CCD line and reading the shadow it casts — a transmitted-light (projection) method, not a laser scan. This page sets out every published specification for the LM-1030, what each number assumes, and the jobs for which this gauge is the wrong tool. Figures below come from the POMEAS LM-1030 datasheet; where the datasheet and the product brochure differ, both are shown.

How the Measurement Works

The transmitter emits collimated green light from a GaN (gallium nitride) LED. The receiver holds a CCD line that images the shadow. Diameter comes from how much of the CCD is occluded. Two consequences follow from this design, and they matter more than the spec sheet:

• Because the CCD integrates continuously during exposure, the reported value is an average over the exposure window. A laser-scan gauge, by contrast, sweeps a moving spot across the part and cannot see what happens between successive sweep lines — the datasheet calls these "invalid detection" gaps.
• There are no moving parts in the optical path. The durability weak point of a laser-scan gauge (the scanning motor) is absent, and the long-life LED supports continuous duty.

That averaging behaviour is why the same gauge can be described both as "2400 samples per second" and as suitable for fast-moving targets: each sample already represents a time-averaged diameter, so brief diameter excursions do not fall between readings.

Published Specifications

A Note on One Conflicting Figure

The LM-1030 brochure headline states "2400 samples per second, ±0.06 µm repeatability", while the specification table in the same document states ±0.15 µm repeatability and ±2 µm measurement accuracy. The conditions attached to the ±0.06 µm figure are not published in the material we hold. The ±0.15 µm and ±2 µm values are the specification-table figures and are the ones used throughout this site. The ±0.06 µm headline is recorded here as a datasheet discrepancy pending confirmation of its test conditions. Treat any vendor repeatability claim the same way: ask what was measured, over what sample count, at what temperature, and on what artefact.

Range: What 0.3 to 30 mm Actually Lets You Do

The gauge covers wire, filament, fine tube, catheter stock, small shaft and pin diameters. The minimum detectable object of 0.3 mm is the floor — below that the shadow is too small relative to the CCD pixel pitch to resolve reliably. At the top, 30 mm is the useful ceiling; a larger product needs either a wider-gauge model or a different principle. For guidance on choosing between the available principles, see inline diameter measurement methods and selection.

Installation Geometry

The transmitter-to-receiver distance of 160 ± 40 mm fixes the working envelope: you need a clear line between the two heads of roughly 120 to 200 mm, and the product must pass through the collimated beam within that gap. The CCD scan distance of about 33 mm is the optical window over which the shadow is read. In practice the constraint that trips up installations is not the gauge — it is product presentation. If the part wanders laterally outside the measurement window, or rotates a non-round section through the beam, the reading changes without the diameter changing. Fixturing the pass-line is part of the installation, not an accessory to it.

What This Gauge Does Not Measure

• Roundness, ovality or lobing. A single-axis projection reads one diameter at one angular orientation. Cross-roll the part or use a multi-axis head if ovality is the tolerance you must hold.
• Internal diameter or wall thickness. Transmitted light sees the outer silhouette only.
• Length, step height or surface defects. These are different instruments; see online gauge, confocal and vision compared.
• Diameter of transparent stock without preparation. Clear material does not cast a clean shadow. The optical behaviour and workarounds are covered in inline measurement of transparent and reflective parts.

Where It Sits Against an Offline Check

An inline gauge earns its place when you need 100% coverage or trend data rather than sampled verification. If the requirement is first-article or lot inspection at a bench, an instant one-click system is usually better matched — the trade-offs are set out in inline versus offline optical measurement. Throughput planning, including how many gauging stations a target rate needs, is worked through in cycle time and station count.

Keeping the Numbers Honest Over Time

A ±2 µm accuracy figure is a statement about the instrument under defined conditions. On a line, drift comes from contamination on the optical windows, thermal growth in the fixture, and product vibration. Calibration interval and drift behaviour are covered in calibration and measurement stability. Plan for verification against a certified artefact rather than assuming the datasheet number survives a year of production untouched.

FAQ

What diameter range does the LM-1030 cover?

0.3 mm to 30 mm, with a minimum detectable object of 0.3 mm. Products below 0.3 mm fall outside reliable resolution; products above 30 mm need a larger measurement window or a different method.

Is ±2 µm the accuracy or the repeatability?

±2 µm is the published measurement accuracy. Repeatability is published separately as ±0.15 µm. These are different quantities: repeatability describes the spread of repeated readings on the same object, accuracy describes agreement with true size. Do not substitute one for the other when writing a tolerance.

Why does the brochure say ±0.06 µm and the spec table say ±0.15 µm?

They are inconsistent in the material we hold and the test conditions for the ±0.06 µm headline are not published. This site uses the specification-table value of ±0.15 µm. The discrepancy is logged; if you are writing a procurement spec, ask the vendor to state the conditions behind any figure they quote.

Can it measure a product moving at speed?

Yes — that is the design case. The CCD integrates continuously during exposure and the gauge runs at 2400 samples per second, so unlike a swept laser scan there is no blind interval between sweeps in which a diameter change could go unseen.

Does it measure roundness or ovality?

Not from a single axis. A projection gauge reads one diameter along one direction at a time. Ovality requires either rotating the product through the beam or using a multi-axis arrangement, and Neither is described as an LM-1030 single-head function in the published material.

What protection rating does the head carry?

IP64. That covers dust ingress and water splashing, which suits most factory environments, but it is not a washdown or immersion rating — confirm against your cleaning regime before installing.

How far apart do the transmitter and receiver mount?

160 ± 40 mm, so a clear gap of roughly 120 to 200 mm between heads. Plan the fixture so the product crosses the beam inside that window and cannot wander out of it.

Next Step

Send the product diameter range, line speed, material and the tolerance you have to hold. POMEAS application engineers can confirm whether the LM-1030 window, sampling rate and accuracy cover the job, or whether a projection image measurement head or confocal route fits better. Start from the LM-1030 product page or the method selection guide.