Dimensional Measurement · Digital Calipers
Digital vernier caliper in 150, 200 and 300 mm ranges with a 0.01 mm display, metric and inch switching, zero at any position, and an IP54 version for wet or dusty work.
A caliper measures the four things that most workshop dimensions come down to: an outside width, an inside bore, a depth and a step. That one instrument covers all four is the reason it sits in every tool crib, and the reason the digital version displaced the vernier is not accuracy but reading time. The scale is read by the instrument and displayed as a number, so the operator spends attention on the part rather than on finding the line that coincides.
What follows from that is a shift in what the instrument is for. A caliper with an encoder is not just a faster vernier; it is a comparator that can be zeroed anywhere, which changes the way a batch of parts is checked.
The instrument is offered in three ranges - 150, 200 and 300 mm - and in three versions distinguished by screen size and by a protection rating. A 0.01 mm resolution is common to all of them, and so is the stated accuracy of plus or minus 0.03 mm.
The range is the first thing to settle, because it sets the physical size of the tool rather than only what it can measure. A 300 mm caliper is 391 mm long and weighs 275 g, which is a different instrument in the hand from the 236 mm, 200 g version at 150 mm. The version then follows from where the tool is used: the IP54 rating exists for work where coolant or dust would otherwise reach the slider, and the material is explicit that the other versions are not rated.
Inside the beam a track of capacitive elements carries a fixed pattern, and the frame that slides along it senses the change in capacitance as it moves. From that the electronics derive a position and display it as a number. Because the encoder reads position rather than counting turns, the reading is available immediately on opening the jaws, and the zero can be moved to any point along the travel.
The jaws themselves are conventional: two for outside measurement, two smaller ones for inside, a narrow rod for depth and a shoulder for steps. The accuracy of the instrument rests on the squareness and flatness of those faces and on the rigidity of the frame, not on the display, which is why a caliper whose faces have worn or been nicked will read consistently but wrongly.
Work backwards from the dimension and the tolerance. The range has to cover the largest dimension to be measured with the jaws still on the beam, and the tolerance decides whether a caliper is the right instrument at all: with a stated accuracy of plus or minus 0.03 mm, dimensions held tighter than that need a micrometer.
Then settle the version. If the tool stays on a bench, the classic form is enough; if it is used at a machine where coolant flows, the IP54 version is the one to specify, because the encoder rather than the jaws is what suffers. Only after those two questions is the screen size worth deciding, and it is a question of where the reading has to be legible rather than of capability.
A caliper measures a distance between two faces in contact with the part, so it is only as good as the contact. A burr, a film of oil, a part that is not clean or a jaw pressed on at an angle all enter the reading, and none of them is visible on the display. Measuring the same point twice is the habit that catches these, since a caliper that is tipped will generally not repeat.
Two figures a buyer would normally ask for are not in the material: the repeatability that accompanies the stated accuracy, and the temperature over which the accuracy holds. A steel beam changes length with temperature, and on a 300 mm instrument that effect is a real part of the uncertainty, so the page states that the figure is missing rather than implying a precision the material does not support.
Every value below is taken from source documentation. Where a parameter is not stated in the available material it is marked as information required rather than estimated.
| Range | 0 to 150 mm, 0 to 200 mm and 0 to 300 mmStandard |
|---|---|
| Resolution | 0.01 mmStandard |
| Accuracy | Stated as plus or minus 0.03 mmStandard |
| Display | Liquid crystal, with an LED backlight and a 1.5 inch or 2.2 inch screen depending on the versionStandard |
| Units | Metric and inch, switchable at the keypad, with automatic conversion between themStandard |
| Functions | On and off by a long press, zero at any position, unit change and backlightStandard |
| Repeatability | Not stated in the material, and it is the figure that follows from the encoder and the jaws rather than from the displayInformation required |
| Temperature behaviour | Not stated in the material, although a steel beam changes length with temperature and this enters the uncertainty on long workInformation required |
| Battery life | Not stated in the material beyond the automatic power-off functionInformation required |
| Beam | Stainless steel, with aluminium core ends described in the materialStandard |
|---|---|
| Jaws | Measuring jaws described as thickened, for outside and inside measurementStandard |
| Depth rod | A 3.5 mm wide depth rod on all three rangesStandard |
| Slider | A thumb roller for traversing the frame, with a locking screwStandard |
| Protection | IP54 on the waterproof version only; the other versions carry no stated ingress ratingStandard |
| Jaw material and hardness | Not stated in the materialInformation required |
| Calibration certificate | Not stated in the material; a traceable certificate is a separate deliverable where readings are relied onInformation required |
| 0 to 150 mm | 236 mm overall, 200 g, outside jaws 40 mm, inside jaws 16 mm, case 25 x 10 x 3 cmStandard |
|---|---|
| 0 to 200 mm | 289 mm overall, 228 g, outside jaws 48 mm, inside jaws 19 mm, case 31 x 11 x 3 cmStandard |
| 0 to 300 mm | 391 mm overall, 275 g, outside jaws 60 mm, inside jaws 21 mm, case 43 x 13 x 3 cmStandard |
| Packing case | A different case for each range; the material notes that the figures given are measured by handStandard |
| Model | Configuration | Key ranges | Availability |
|---|---|---|---|
| Classic 1.5 inch | Stainless steel beam with a 1.5 inch liquid crystal display and LED backlight | 0 to 150, 0 to 200 and 0 to 300 mm; 0.01 mm resolution; plus or minus 0.03 mm | The base form, where the reading is taken at the tool and a large screen is not needed |
| Large screen 2.2 inch | The same instrument with a 2.2 inch display | As the classic version | The form for work where the display is read at a distance or in poor light |
| Waterproof IP54 | Sealed slider and body for wet or dusty work | 0 to 150, 0 to 200 and 0 to 300 mm; the protection rating applies to this version only | The form for machine-tool and outdoor use; the material states explicitly that the other versions are not rated |
| Fast-reading electronics | Described in the material as carrying a faster reading chip | Not distinguished from the other versions in the material | Carried as described; the material does not state how the reading speed differs |
Certifications are only published once a certificate copy can be produced, so this section is deliberately empty rather than populated with assumed approvals. Tell us which approvals your application requires and we will confirm what is available for this instrument.
The following are required for a complete specification but are not stated in the documentation supplied to us. They are listed rather than estimated:
Both measure the same four things - outside, inside, depth and step - with the same jaws; they differ in how the value is read. A vernier caliper is read from a graduated main scale against a sliding secondary scale, which requires the operator to find the line that coincides and to interpolate. A digital caliper reads its own position and displays the value, with a resolution of 0.01 mm, and it can be zeroed at any point. The trade is that the digital version depends on a battery and an encoder, while the mechanical vernier has nothing to fail.
When the work puts the slider in contact with coolant, water, dust or swarf. The measuring jaws are the same on all versions; what the rating protects is the encoder and the display, which is where contamination causes the reading to jump or to stop updating altogether. The material is explicit that the protection applies to the waterproof version only, so a buyer who intends to use the tool at a machine has to select that version rather than assume the rating applies across the range.
It makes the caliper read a departure rather than an absolute size. With the jaws closed on a reference - a nominal bore, a setting piece or a first part - the display is zeroed, and every subsequent reading is the difference from that reference. This is the standard way of sorting a batch against a limit, since a tolerance can be read directly instead of being measured and then subtracted. It does not make the instrument more accurate; it changes what the number means.
The resolution and the accuracy are different figures, and on this instrument they differ by a factor of three: the display resolves 0.01 mm while the stated accuracy is plus or minus 0.03 mm. A resolution finer than the accuracy is normal and is there so that repeat readings do not have to be rounded by eye, but it does not mean the instrument can hold a 0.01 mm tolerance. Where that tolerance is the requirement, a micrometer or a comparator with the right reference is the appropriate instrument.
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