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How a digital arch gauge works

A digital arch gauge precisely measures radii and diameters using electronic sensors and digital displays. It provides immediate, accurate readings, simplifying alignment and dimensional inspection operations in engineering and industrial applications.

The digital arch gauge measures radii of curvature and diameters using the principle of the circle passing through three points.

The digital arch gauge is a precision instrument for measuring diameters and radii of curvature in all cases where a calliper or micrometer cannot be used.

To measure a radius or a diameter (1), simply place the digital arch gauge (2) on the surface of the object to be measured.

The electronic controller of the digital arch gauge stores the chord value (3) corresponding to the distance between the two support points.
The chord value depends on the type of accessory fitted to the digital arch gauge and allows it to adapt to small, medium or large radii.

The electronic controller measures the displacement of the rod (4), located exactly at the centre between the two supports.

The microprocessor installed in the electronic controller calculates the radius or diameter by applying a trigonometric formula.

The measurement is instant and can be displayed in either mm or inches, as either a diameter or a radius value.

The arch gauge is a measuring instrument that can be used even by non-specialist staff, and in a few seconds it provides measurements that could otherwise only be obtained by comparison with physical models of known radii (comparison templates).

Measurements can also be taken on profiles with variable radii, provided the radius remains constant over the section on which the instrument rests.

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Choose the DIACHECK-CT arch gauge suited to your application

The DIACHECK-CT series includes versions for small, medium and large radii, with dedicated arches and accessories and a measuring range from 100 to 10,000 mm. Go to the product page to compare the models and find the one best suited to your measurement requirements.

→ Go to the arch gauge product catalogue

Technical characteristics

This radius gauge gives a direct, instant reading of the inside or outside radius for a wide range of curves, profiles, diameters and cylindrical objects.

Convenience: there is no need to cut out templates to find the radius of a curve, nor to remove the part from the machine to measure it, nor to take the part out of its installed position (buried pipes, installed tanks, rolling machines already positioned and fixed, for example)
Ease of use: it is easy to use and the measuring process is extremely quick. Simply place the gauge inside or outside the curve to obtain the radius of curvature, or the diameter of the object, automatically.
Any material: the gauge is suitable for any type of solid material such as steel, wood or plastics.
High accuracy: the margin of error on the radius is only 0.1 mm (measuring accuracy depends on the surface quality of the solid being measured; to obtain maximum accuracy the surface must be free of dips and of high surface roughness).
Field of application: this radius gauge is supplied with different measuring arches and different contact angles. Using the various arches gives a measuring range between 100 and 10000 mm.

Innovative and versatile

Instant reading with the digital dial indicator: It allows immediate, precise reading of measurements, reducing the margin of human error.
Easy to programme and use: it simplifies the measuring process thanks to the intuitive digital interface.
User-friendly : It does not require advanced technical skills to be used effectively. Ideal for maintenance operators and technicians who need a reliable, easy-to-use instrument.
Handling several radii of curvature: a single instrument can be used to measure different radii of curvature, making it extremely versatile and cost-effective.

Typical applications

Measuring the radius of curvature of bent tubes.
Measuring the outside diameter of tubes and pipes (even when already installed or buried).
Measuring the inside diameter of ribs and large tubes.
Measuring the radius of curvature of curved sheet metal.
Measuring the diameter of large tanks or silos, both while the individual parts are being built and during assembly and positioning.

Measuring the radius of curvature of molded or thermoformed plastic parts.
Measuring the radius of curvature of rolled and bent beams.
Measuring the shape of molded parts or curved sheet metal for the furniture industry.
Measuring the curvature of glass or of items with complex geometric shapes.
Checking and comparing the mathematical model of geometric shapes produced by CNC.
Checking the curvature of tubes and fittings.

Success stories

Measuring the curvature of glazing and of mating profiles.
Measuring the radius of curvature of body panels and sheet metal parts for the automotive industry.
Measuring the diameter of ribs for tunnels or for construction.
Measurement of the radius of curvature of cement and concrete products.
Measurement of the radius of curvature or diameter of parts for the marine industry or the construction of large structures.

Measurement of the radius of curvature of profiles during processing on profile bending machines, press brakes and forming systems.
Measurement of pipe diameter and coupling taper for the transport of hydrocarbons, water and liquids.
Measurement of the taper of coupling flanges for pipes or tanks.
Measurement of the diameter or radius of curvature of rolled or welded products.
Verification of the correct assembly of parts during coupling and sealing.

Frequently asked questions

How does a digital arch gauge work?

It measures radii and diameters using the principle of the circle passing through three points: when it is placed on the surface, the electronic controller detects the displacement of the central rod relative to the known chord and calculates the radius or diameter with a trigonometric formula, with instant reading in mm or inches.

What is the measuring range of DIACHECK-CT arch gauges?

Using the different measuring arches, the range goes from 100 to 10,000 mm, for both internal and external radii and diameters.

How precise is a digital arch gauge?

The margin of error on the radius is approximately 0.1 mm; the actual precision depends on the quality and roughness of the surface being measured.

When is it better to use an arch gauge instead of a calliper or micrometer?

When a calliper or micrometer cannot be used: pipes already installed or buried, tanks and silos, ribs, rolled sheet metal and curved profiles, without removing the part from the machine.

Which materials can it be used on?

Any solid material: steel, wood, plastics, glass, cement and concrete, and curved products.

Contacts & Information

Contact for general information : info@roder.it

Machine Vision Division of RODER : www.rodervision.com
RODER Instruments Division : www.innovacheck.com
More about RODER : about us

The information contained in this website is provided for information purposes only. Although it has been prepared with the greatest care, it does not constitute a contractual offer or a binding commitment to supply. It may contain transcription, translation or typographical errors. For precise and up-to-date information, please contact our company directly.

Note: Some images on this website have been intentionally generated using artificial intelligence (AI). This is because, for many applications and projects, photographs of the actual installation or system cannot be disclosed owing to confidentiality agreements, contractual clauses and non-disclosure agreements (NDAs).