You’ve just bought a digital caliper, but you’re not sure if the readings it has been giving you are accurate. When working with systems on a car such as the brake system, you need an absolutely accurate digital caliper. Digital calipers can be checked for accuracy by calibrating them. This process of calibration is quite easy to accomplish. The following paragraphs describe the steps that you will need to follow to properly calibrate a digital caliper. There is also a short paragraph describing the proper use of a digital caliper.
Step 1 - Clean Caliper Pads
Calipers are designed to measure to extreme degrees of accuracy. Some calipers will measure to an accuracy of up to five decimal digits, or one hundred thousandth of an inch. Having clean contact surfaces when measuring or calibrating to this degree of accuracy is imperative. Use a clean and lint free cloth to wipe off the contact pads.
Step 2 - Unlock the Calibration Slide
On the fixed portion of the digital caliper is a locking lever that locks the fixed contact pad. This needs to be unlocked in order to calibrate the digital caliper.
Step 3 - Close the Caliper Completely
Screw down on the adjustment knob until the moving portion of the digital caliper is as far as it will go.
Step 4 - Press Fixed Pad against Moving Pad and Lock
Press down on the movable portion of the locking fixed pad until it makes firm contact with the moving pad portion. While keeping pressure against the moving pad, swivel the locking lever to lock the stationary pad in place.
Step 5 - Set Indicator to Zero
With the moving and stationary contact pads making firm contact and firmly locked in place, rotate the knob or press the reset button until all digital readout digits are at 0.
Step 6 - Verify Digital Caliper Calibration
Most professional digital calipers come with two or three calibration rods. The sizes that these rods come in will depend on the range that the digital caliper is capable of reading. Digital calipers in the automotive industry will read from 0 to 6-inches. Smaller digital calipers, such as ones that only read to 1-inch, may only have one calibration rod, which will normally be 0.5-inches long, to an accuracy of how many decimal points that the digital caliper is capable of. Larger digital calipers may also have a half inch calibration rod, plus an additional one or two inch calibration rod.
Using Your Digital Caliper
Below are the proper steps for use of a digital caliper:
- Open the caliper jaws.
- Slide the caliper over the work piece being measured.
- Turn the knob to close the caliper jaws until initial contact is made with the piece being measured. Don’t over-tighten the adjustment knob.
- Caliper pads should slide across piece with slight pressure.
- Read the digital readout.
Obtaining accurate readings with a digital caliper requires proper calibration and use. The preceding paragraphs contain the information to do both.