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114 Part II: Metrology
• Calibration
interval prompt
• Calibration
documentation
and history
• Calibration
work order
• Process
equipment
• Calibration
equipment
• Calibration
procedures
• Calibration
environment
specifications
• Calibration
status
indicators
Part II.F.1
Inputs
Process
Calibration
Feedback
Verification of
measurement equipment
operation
Outputs
Calibrated
equipment
Figure 12.1 The calibration system.
2. Importance in process operation
3. Manufacturer guidelines or requirements
4. Historical performance accuracy and consistency
The duration of a calibration interval may be shortened at the discretion of an
equipment owner, calibration laboratory manager, or other authorized individual
within an organization. There are a number of techniques in use to establish calibration
intervals initially and to adjust the intervals thereafter. These methods
include using the same interval for all equipment in the user’s inventory, the same
interval for families of instruments (for example, oscilloscopes, digital voltmeters
[DVMs], gage blocks), and the same interval for a given manufacturer and model
number. Adjustments of these initial intervals are then made for the entire inventory,
for individual families, or for manufacturer and model numbers, respectively,
based on analysis or history. A study conducted for the NIST in connection with
a review of government laboratory practices identifies these and other methods
(Vogt 1980). It is generally not possible or advisable to lengthen the duration of a
calibration interval without a detailed analysis of equipment performance and, in
the case of regulatory control, authorization by an agent of the cognizant department
or agency.
The actual prompt initiating the calibration process may be electronic or in
hard-copy form. Electronic information systems supporting modern industrial
operations most commonly track equipment in relation to established calibration
intervals and prompt appropriate individuals when calibration is required. Paperbased
information systems supporting industrial operations for calibration require
the establishment of a “tickler” file system. A tickler file is most commonly some
form of card index wherein each piece of equipment with a calibration interval has