Precision Spherometer

Quick answer: The Precision Spherometer is a mechanical measuring instrument used to determine the radius of curvature of spherical surfaces, such as lenses and curved mirrors, using a central micrometer screw referenced against three fixed outer legs.

Description

The LabEquip Precision Spherometer works by placing its three fixed outer legs on a spherical surface while a central micrometer screw is adjusted until it just touches the surface. The height (or sagitta) of the central screw relative to the plane of the three legs is measured, and combined with the known spacing between the legs, students calculate the radius of curvature of the surface.

This makes it a core instrument for optics practicals in physics laboratories, where measuring lens or mirror curvature is a standard exercise. The instrument also gives students hands-on practice with screw-gauge concepts such as pitch, least count, and zero error, and reinforces good practice around repeated observations and measurement uncertainty.

Specifications

Care & Maintenance

Handle the central screw gently and avoid over-tightening it against a surface, as this can damage both the instrument and the sample being measured. Store the spherometer in its case when not in use, keep it dry, and periodically check for zero error before taking readings.

Why Choose LabEquip

LabEquip supplies precision physics measuring instruments to schools and colleges, with a straightforward buying process and a sales team that can confirm exact specifications before you order. Explore more of our range below:

• LabEquip home page – browse our full lab equipment range
• High-Resistance Coil Unit – another core physics lab measurement component
• STEM Kits category – more hands-on classroom teaching resources

Frequently Asked Questions

What does a spherometer measure?

It measures the radius of curvature of a spherical surface, such as a lens or curved mirror, by comparing the height of a central screw against the plane formed by three fixed outer legs.

What is the least count of this spherometer?

The exact least count is not specified for this listing. Please contact our sales team to confirm the specification before you order.

What is “zero error” and why does it matter?

Zero error is the reading shown when the central screw touches a flat surface (where curvature should read as zero); checking and accounting for it improves the accuracy of subsequent curvature measurements.

What can I measure with this instrument besides lenses?

A spherometer can also be used, with suitable technique, to measure the thickness of thin plates or sheets, in addition to its main use for surface curvature.

What class level typically uses a spherometer?

Spherometers are standard equipment in higher-secondary and college-level physics laboratories, particularly for optics practicals.

How should I store the spherometer between uses?

Store it in its case in a dry location, avoid dropping or knocking the central screw mechanism, and periodically check for zero error to keep future measurements accurate.

Last Updated: September 2026