Parts of a Vernier Caliper
- Main scale: the fixed ruler scale in millimeters (or inches) that gives the whole number reading.
- Vernier scale: the sliding scale that provides the fine decimal reading, typically accurate to 0.02mm or 0.05mm.
- External jaws: used to measure the outside dimension of an object.
- Internal jaws: used to measure the inside dimension of a hole or opening.
- Depth rod: extends from the end to measure the depth of a hole or recess.
Step-by-Step: How to Take a Reading
- Close the jaws gently on the object being measured, or place the depth rod into the hole.
- Read the main scale first: note the whole millimeter value just before the zero mark on the vernier scale.
- Find where a line on the vernier scale aligns exactly with a line on the main scale; this gives you the decimal part of the reading.
- Add the main scale reading and the vernier scale reading together for the final measurement.
- For digital vernier calipers, simply read the value directly from the LCD display, though understanding the analog method is still useful when the battery dies.
Common Mistakes to Avoid
- Applying too much pressure on the jaws, which can compress soft materials and give a false reading.
- Reading the wrong aligned line on the vernier scale, especially when multiple lines look close together.
- Not zeroing the caliper before use, which can introduce a consistent offset error.
- Using a caliper with worn or damaged jaws, which reduces accuracy.
