TOLERANCE OR MAXIMUM PERMISSIBLE ERROR OR ACCURACY OF VERNIER OF DIGITAL CALIPER AS PER BS EN ISO 13385-1:2019

 Calliper 

Measuring instrument which evaluates a dimensional quantity of an internal or external feature of the basis of opposing contact from the movement of a slider with a measuring jaw, moving relative to a measuring scale on rigid beam and to a fixed jaw.

Maximum permissible error (MPE) values apply to any indication permitted for use of calliper as defined by the manufacturer and when used in accordance with the manufacturer's recommendation .The MPE Values cannot be smaller than the digital step or the scale interval on the circular scale or vernier scale

There are mainly three Error are consider in the calliper

1. .Partial Surface contact error , E (limited by  E_MPE)
2. Shift Error ,S (limited by  S_MPE)
3. Line Contact Error

DEFAULT MPE (Maximum Permissible Error ) for metrological characteristics

If no MPE values are otherwise stated then the values in tables apply for callipers with a measuring range up to 1000 mm and with analogue scale interval or digital step of 0.01 mm ,0.02 mm or 0.05 mm.

For the MPE values in Table the decision rule that applies when demonstrating conformity or non conformity to specification shall be simple acceptance and rejection, with the measurement capability index, "cm," being four or larger, in accordance with ISO /TR 14253-6.The measurement uncertainty the test values shall be evaluated in accordance with ISO 14253-5

NOTE  : The MPE values in Table include a simple acceptance and rejection decision rule in accordance with ISO / TR 14253-6 . This is an example of starting a decision rule other than the default rule of ISO 14253-1

The Maximum Permissible Error  Values for callipers with measuring range up to  1000 mm

Measured Length,(l ) mm	Analogue Scale interval or Digital Step
	0.01 mm		0.02 mm		0.05 mm
	EMPE   µm	SMPE   µm	EMPE   µm	SMPE   µm	EMPE   µm	SMPE   µm
0 ≤ l≤50	±20	±30	±20	±40	±50	±50
50<l≤100	±30	±50	±40	±60	±50	±100
100<l≤200	±30	±50	±40	±60	±100	±100
200<l≤300	±40	±60	±40	±60	±100	±100
300<l≤400	±40	±60	±40	±60	±100	±100
400<l≤500	±50	±70	±60	±80	±100	±100
500<l≤600	±50	±70	±60	±80	±150	±100
600<l≤700	±60	±80	±60	±80	±150	±150
700<l≤800	±60	±80	±60	±80	±150	±150
800<l≤1000	±70	±90	±80	±100	±150	±150

The Maximum Permissible Error of Line Contact Error (Paralleslism)

The Line contact is calculated as the range of the measured values. The MPE value for line contact error is equal to the range of E_{MPE. That is if}  E_{MPE =} ± a

Then the MPE for line contact error is 2a

Example : The maximum permissible error of Partial Surface contact error (E_MPE) of 150 mm Digital Calliper is ±20 µm,

The Maximum Permissible error of line contact error is 2*20 

That is 40 µm