Suppose you need to measure the inner and outer diameter of copper tubing or the outer measurements of an element you’re currently machining. That’s where your trusty caliper comes in, as it allows you to take an accurate measurement of whatever you’re measuring — length, width, or depth measurements.

However, if you’re new to calipers or are in the market for one, you should know that several different types of calipers are available on the market. This article aims to touch upon different types of calipers, their use, their advantages, and drawbacks, and help both newbies and those well-versed, make an informed decision when purchasing a new precision measuring instrument.

Different Types of Calipers

In general, calipers are precise measurement tools that can accurately measure up to a hundredth of a millimeter (0.01mm) or a thousandth of an inch (0.001”). They’re usually composed of a calibrated metric and inch scale attached to the upper jaw and a lower jaw that slides along the main scale and directly reads the distance measured in high accuracy and precision.

These readouts are then either derived from the Vernier scale or displayed on a TESA dial or an LCD display. All calipers are functionally identical, with different measuring ranges (0-6” or 0-12”) and different ways of reading the result.

What Is a Vernier Caliper?

The Vernier caliper, often referred to as an analog caliper, is the most standard among different types and requires some practice before proper use — which is why machining and metalworking schools have a period or two dedicated to Vernier caliper readouts.

The readout is quite simple; just read the pointer's position directly on the scale. When the pointer is between two markings, you can mentally interpolate (determine an unknown value given knowledge of surrounding data points) to improve the readings. However, the universal practice dictates the addition of a Vernier scale on the sliding jaw to allow for accurate interpolation, usually in 0.02mm or 0.001” increments.

What Is a Dial Caliper?

Instead of using a Vernier scale, which admittedly requires practice, dial calipers read the final fraction of a millimeter or an inch on a simple dial. The need for a Vernier scale is eliminated by the use of a miniature, precise rack and pinion that drive a pointer on a circular dial, allowing a direct readout. These dials typically rotate every inch, tenth of an inch, or a millimeter, depending on the type of caliper you bought.

The dial indicator measures only fractions, so they have to be added to the whole inches of millimeters read directly from the scale. A good thing about dial indicators is that they can be used for differential measurements — a machinist could rotate the dial beneath the pointer and measure the plus-minus variance in size relative to the master measurement.

What Is a Digital Caliper?

Rather than a simple Vernier scale or a rack and pinion driving a dial, digital calipers use a linear encoder and a digital display to show the readings as a numeric value. Though they usually have the main slide scale, its role in digital calipers is obsolete. However, this hand tool encapsulates all the practical features of previous types.

For example, the measurements can be displayed and converted between millimeters, centimeters, and inches. They also have a zeroing capability at any point along the slide, allowing the same sort of differential measurements as we’ve seen with the dial calipers. Additionally, they may have a “reading hold,” allowing users to take measurements in awkward locations and situations in which an LCD display can’t be seen and read the measurements post-use.

Another fantastic feature offered by higher-end digital calipers is interfacing with a dedicated recorder or a personal computer, which improves the reliability of records or their import in various spreadsheets, statistical process control programs, and other types of software.

Key Differences Between Dial, Digital, and Vernier Calipers

Regardless of their type, whether they’re a Vernier, dial, or a digital, all standard-use 6-inch calipers are made of stainless steel with a rated accuracy of 0.02mm or 0.001 inches and a resolution of 0.01mm or 0.005 inches.

Another noteworthy caliper type is micrometer calipers, which measure in thousands of a millimeter (0.001mm) or ten-thousands of an inch (0.0001”), but they’re generally regarded as an entirely separate category. To learn more about the differences between calipers and micrometers, please refer to our Micrometers vs Calipers: Understand the Key Differences guide.

The Vernier, digital, and dial calipers are functionally identical, but there are notable differences in the readout, scale working principle, and price.

Readings

Reading a Vernier caliper takes some practice, as the decimal numbers need to be derived from the Vernier scale. Dial calipers are somewhat easier, as the decimal numbers are instantly shown on the dial and added to the whole number read on the sliding scale. Digital calipers offer the easiest and fastest reading, as the display instantly shows the reading.

Ease Of Use

Vernier calipers are by far the hardest to use due to their readings and are nearly impossible to adequately calibrate once a zero-point error occurs. On the other hand, both Dial and Digital are pretty straightforward to calibrate to zero, though digital calipers are generally easier to use due to their instantaneous readings from a single scale (in this case, an LCD display).

Use Conditions

Vernier calipers for the win in this category, as they’re effective in almost any conditions, aren’t affected by magnetic fields, and are mildly shockproof since they don’t have intricate moving parts as dial calipers do. The same can be said for digital calipers, though they are sensitive to magnetic fields, water, dirt, and oil and require a power source (a battery) to function. Dial calipers stand in the middle between the two. They’re resistant to water, dirt, and oils but are very sensitive to magnetic fields and shocks.

Price

The price depends on several different factors, such as brand name, build quality, accuracy rating, etc. Generally speaking, digital calipers are the most expensive of the three types mentioned in this guide, while Vernier calipers seem the most affordable. However, the aforementioned factors should be considered, as there are high-end Vernier calipers that are pricier than affordable digital calipers of questionable quality.

Pros of Vernier Calipers

Vernier calipers have fewer moving parts, and thus they’re unlikely to go out of calibration or malfunction (unless severely damaged). They also require no batteries to function, so you won’t suffer any downtime due to dead batteries.

Pros of Dial Calipers

Dial calipers also don’t require batteries and are generally easier to read than Vernier calipers. They’re also very easy “to zero” but may have calibration issues if the tool is dropped and the rack and pinion misalign.

Pros of Digital Calipers

The pros of digital calipers are quite evident. They’re incredibly easy to read, offer several features not included in other types, have a built-in measurement conversion system, and are generally very easy to calibrate and zero. However, they’re also incredibly sensitive and require you to always keep spare batteries in your tool kit.

Summary

Ultimately, there isn’t a single “better” type of caliper; all have their distinct advantages and drawbacks, and determining the best type of caliper for you largely depends on your applications. For example, Vernier calipers are incredibly reliable, accurate, and great for all conditions. On the other hand, digital calipers are the most versatile of the three.

DIYers would most probably benefit the most from an averagely-priced digital caliper, as they’re the easiest to use. On the other hand, machinists know precisely what tool they need, which is why machine shops usually have several different indicators and calipers suitable for various applications.

If you want to learn more about calipers, micrometers, and other measurement systems, visit Reid Supply — in addition to offering more than 40,000 different parts and components, the company also has an extensive library of guides, catalogs, and professional literature available for download.