The Name for a Calibration - Bootstrapping or Comparison

[Wes Bucey]

In Reply to Parent Post by Jim Wynne

Once again...

If you compare something to a standard, you're calibrating it. What you refer to as "verification" is not different from calibration; it's a form of calibration. Where an act of calibration takes you will vary with the criticality of the measurements and other factors. Perhaps adjustment (a form of repair) will be necessary. Perhaps calculation of uncertainty values will be necessary. Perhaps relatively elaborate record keeping will be necessary.

On the other hand, in some instances, just holding one thing up against another is enough, and it's still calibration.

One caveat--these things might be defined locally in ways that are at odds with standard denotation. For instance, a company's measuring and test equipment requirements might differentiate between calibration and verification and describe the requirements for each. This is a wrong thing to do, imo, because it's just as easy to define the requirements for different types or classes of devices and call it all "calibration."

OK. Citation for my comfort zone, please?

[Jim Wynne]

In Reply to Parent Post by Wes Bucey

OK. Citation for my comfort zone, please?

calibrate(kl-brt) 1. To check, adjust, or standardize a measuring instrument, usually by comparing it with an accepted model.
2. To measure the diameter of the inside of a tube.


The American Heritage® Science Dictionary Copyright © 2005 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.

[Wes Bucey]

In Reply to Parent Post by Jim Wynne

calibrate(kl-brt) 1. To check, adjust, or standardize a measuring instrument, usually by comparing it with an accepted model.
2. To measure the diameter of the inside of a tube.


The American Heritage® Science Dictionary Copyright © 2005 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.

Affirmed by NIST (http://www.itl.nist.gov/div898/handb...glossary.htm#C) calibration In metrology, the process or method for comparing actual readings to their known values, and also of making suitable adjustments so that the agreement between the two is improved.

[AndyN]

Surely, if the OP is using unknown condition gauge blocks and then measuring them with a micrometer which is calibrated, he's not got a 'standard' at all. The micrometer should resolve to 4:1 or better. He can't discriminate 0.001 which is the tolerance he's seeking. It's better to use the VIM definition, I'd suggest this:

The International Vocabulary of Metrology – Basic and General Concepts and Associated Terms (VIM) defines calibration as: the operation that, under specified conditions, in a first step, establishes a relation between the quantity values with measurement uncertainties provided by measurement standards and corresponding indications with associated measurement uncertainties and, in a second step, uses this information to establish a relation for obtaining a measurement result from an indication.1
To simplify, calibration:
Uses traceable standards or reference materials
Follows a specified procedure
Determines if the performance of the item being calibrated meets the required
specifications

[Jim Wynne]

In Reply to Parent Post by AndyN

Surely, if the OP is using unknown condition gauge blocks and then measuring them with a micrometer which is calibrated, he's not got a 'standard' at all. The micrometer should resolve to 4:1 or better. He can't discriminate 0.001 which is the tolerance he's seeking.

How do you know what the resolution of the micrometer is? I've never seen one that couldn't resolve to .001 and most can do .0001.

It's a fairly simple thing--if the micrometer could be used to perform the task at hand, would it be suitable in terms of accuracy and precision? If so, then calibrating (yes, calibrating) the gage blocks against it shouldn't be an issue. If you have a need a block stack of say, three inches ±.001, and you use a micrometer that's accurate to .0001 to measure the block stack and the result is 3.0002", where's the problem?