How to classify the accuracy of digital calipers?

The accuracy classification of digital calipers is mainly based on their resolution and allowable error (indication error), and different standards (such as international ISO, Chinese GB, Japanese JIS, etc.) have slightly different definitions of accuracy levels. The following are common classifications and key parameters:

1. Classified by resolution (minimum display unit)

Resolution is the minimum measurement unit that a digital caliper can display, which directly affects the reading accuracy:

0.01mm (0.0005 inch): The most common high-precision model, suitable for general industrial measurement.

0.005mm (0.0002 inch): Ultra high precision, used for precision machinery, electronic components, etc.

0.001mm (0.00005 inch): Very rare and requires special environmental support (such as a constant temperature laboratory).

Attention: Resolution ≠ actual accuracy, and comprehensive evaluation based on indication error is also required.

2. Classified by accuracy level (indication error)

According to the international standard ISO 13385 or the Chinese standard GB/T 21389-2008, the accuracy levels of digital calipers are usually divided into the following two categories:

(1) Ordinary precision level

Indication error: ± 0.02mm (within the measurement range of 0-200mm).

Repetitive error: ≤ 0.01mm.

Applicable scenarios: Conventional machining, quality inspection, etc.

(2) High precision level

Indication error: ± 0.01mm (within the measurement range of 0-200mm).

Repetitive error: ≤ 0.005mm.

Applicable scenarios: precision molds, aerospace parts, etc.

Example of Key Parameters (Using 200mm Range as an Example):

Grade indication error, repeatability error

Normal accuracy ± 0.02mm ≤ 0.01mm

High precision ± 0.01mm ≤ 0.005mm

3. Other factors that affect accuracy

Range: The error increases with the increase of measurement length (such as a range error of ± 0.03mm for 300mm).

Environmental conditions: temperature changes (such as ± 1 ℃ which may result in a 0.001mm error), vibration, dust, etc.

Calibration cycle: It is recommended to calibrate regularly every year (refer to JJG 30-2012 Verification Regulations).

4. Selection suggestions

Clear requirements: Choose 0.01mm resolution and ordinary precision level for general industrial use; High precision grade is selected for precision manufacturing.

Certification mark: Priority should be given to products with CE, ISO, or GB certification.