How To Calibrate Digital Calipers | Things You Should Know

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People in workshops usually take lots of measurements of different items, and using the best digital caliper can give the most accurate results. 

Digital calipers are ideal for taking dimensional measurements of any component or different parts of products in a workshop. However, this measuring instrument can wear out easily because of frequent use or external factors like temperature, which affect its accuracy. 

It’s always recommended to calibrate calipers regularly to maintain their precision. Most commercial workshops use traceable digital calipers that must be calibrated in a certified calibration laboratory. 

But, if you’re looking for in-house calibration, we’re here to help you. In today’s article, we’ll discuss everything about digital caliper calibration, from the required tools to the calibration process. 

So, without wasting any more time, let’s get started! 

Digital Calipers Calibration Requirements

Digital caliper that needs repair
Homesthetics | Anton Giuroiu

The main purpose of calibrating a digital caliper is maintaining its metrological properties. In that way, you keep the mean value of the maximum permissible error (MPE) constant, which includes Scale Shift and Surface Contact Errors. Thus, you get accurate figures for inside, depth, and step measurements. 

Calibration ensures that the caliper will stick to the MPE value and during calibration, you must calculate the actual error for precise measurements. Frequent use of the caliper affects its measurement accuracy and causes long-term damage to the instrument, so the caliper measurements can be erroneous if it’s not calibrated at regular intervals. 

Materials Needed For Caliper Calibration

1. Gauge Blocks

Using a gage block is the best way to calibrate a caliper and you can also use gage blocks to calibrate dial calipers or vernier calipers. Make sure to prepare the gauge blocks in Grade AS1 or Grade 0 in a length that matches the caliper’s maximum length. 

2. Caliper Checker

You can also use check master or caliper checkers instead of gauge blocks because they are more accurate. The length of your check master should determine the maximum length of your caliper during calibration. 

3. Step Masters And Depth Micro-Checkers

If you know how to repair digital vernier caliper, you must be well-acquainted with using step masters for micrometer calibration as well as verification. It is convenient for step and depth measurements of the caliper. 

4. Gauge Block Holder

It is used to stack the gauge blocks inside the half-round caliper jaws at the necessary length for the calibration procedure. 

5. Plug Gauge Or Pin Gauge

A plug or pin gauge checks the critical points on the measuring faces of a caliper’s jaws much more accurately than a gauge block. It has a single point of contact on the measuring face because of its even, round shape. 

6. Surface Plate

A surface plate is used for the depth measurement of a vernier or dial caliper. It usually functions as a datum plane when calibrating the tool using a caliper checker or gauge blocks for precision measurements. 

7. Hygrometer And Thermometer

Environmental conditions, like temperature and humidity, play a major role in determining the correct readings using a caliper. That’s why caliper calibration is done in a controlled environment. The temperature is maintained at 68℉ using a thermometer, and the relative humidity must be 30 to 50%, which is monitored with a hygrometer. 

8. Datasheet

You need to record all the calibration data using a checksheet or a datasheet to verify whether it satisfies the standard measurement values. It is easier to adjust the values if you have a record of the calibration data. Nowadays, you can use any calibration software to record the data and easily avoid errors. 

Preliminary Inspection Of Dial Or Vernier Calipers

The calibration process starts with visually inspecting the dual or vernier caliper to check whether the equipment is in good condition. It will help you determine if the caliper requires many repairs. 

Inspect each component to ensure that nothing is broken or missing. If any component has worn out, the caliper needs repair and not calibration. Next, check whether the vernier scale and the graduations are distinctly visible on the caliper. 

If you already know how to read a digital caliper, change the caliper batteries or clean the LCD screen to make sure that the readings are visible. But, for a dial caliper, place it on a surface plate without any vibration, and if the indicator needle moves, it must be adjusted. 

You also need to check the smooth sliding movement of the caliper’s movable jaw because a flat beam or any foreign material can affect the sliding moment. Moreover, inspect the equipment for dents or dirt before using a lint-free cloth along with isopropanol to remove the dirt, and an Arkansas stone to fix dents and nicks. 

Caliper Calibration Procedure

Check the relative humidity and temperature of the room where you plan to conduct the entire procedure and adjust the conditions accordingly to maintain a controlled environment. Also, record the calibration date and time on the datasheet to conduct the calibration at regular intervals. 

Prepare the gauge blocks, plug gauge, or pin gauge based on the maximum length of the caliper. Use the caliper checker to adjust the length as indicated in the datasheet. You can also use the gauge holders to keep the gauge blocks or plug gauge in place. 

Next, adjust the caliper to the zero setting to calculate the standard calibration values. It’s easier with a digital caliper because you simply need to push the “0” button near the screen after closing the caliper jaws. By setting the value at zero, you’re essentially standardizing the caliper to get an accurate measurement. 

Now, start collecting and recording data for inside, outside, step, and depth measurements. After gathering all the data, you must evaluate them and determine the final calibration result. 

How To Calibrate Digital Calipers Frequently Asked Questions ?

What is calibration?

Calibration is a technique that helps to ensure that measuring equipment, like a caliper, can perform to its optimal level and provide accurate measurements within allowable tolerances specifications. It is determined by using any reference standard, such as a gauge block or a pin gauge. 

When does a caliper need calibrating?

When you see that the readings of a caliper are erroneous, but the tool itself is in top condition, it’s time to calibrate the instrument. Frequent uses can affect the calibration of a caliper, which will hamper its accuracy. So, it’s best to calibrate it regularly to maintain the standard values. 

How to prepare a digital vernier or dial caliper for calibration?

Make sure that the caliper is clean by removing all dirt and foreign materials using a lint-free cloth. Next, keep the caliper’s lower jaws parallel to each other and verify the alignment of their measuring faces. Then, prepare the checksheets and check the humidity and room temperature before starting the calibration process. 

How To Calibrate Digital Calipers Final Thoughts

The calibration process helps to standardize the measurement errors so that the caliper can offer accurate figures while measuring the different dimensions of an item. Calipers often go haywire and show erroneous figures when they are frequently used in a workshop. 

When the measuring tool gives erroneous results, check the conditions of its individual components. If some of the components are missing or damaged, calibration won’t be enough to fix the problem, and you need to repair the instrument. 

On that note, we’ll sign off. Take care and see you next time!