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Calibration Basics Part II - Adjustment

Calibration Basics Part II - Adjustment

This is Part II of our Calibration Basics series. In the last post, we looked into the general overview of what calibration is. While a rather simple concept, it is still extremely important to keep those basics straight.

In this post, we will dive into what happens when your calibration process finds a piece of equipment to be reading off.

If you have been reading along, in the previous post, you know that we dove into the basics of what calibration is. To demonstrate this, we used an (admittedly cheesy) example of a simple bathroom scale.

The problem is, not every time you calibrate something will it be reading exactly what you need it to be. What happens then? Pretty simple. You must adjust it.


Back to the example. Let's say you got lucky and during the calibration process, you find that the scale was reading 5 pounds too heavy. Phew. All of that hard work you put in to losing weight was not in vain. After a brief moment of rejoice, you now realize that you have two options:

  1. Live with it and always subtract 5 pounds from your reading.
  2. Adjust the scale to read accurately.

I think most of us would prefer the second option. Who wants to do math after a hard workout, anyways?

So, how does the calibration procedure address this? It doesn't. If you refer back to the formal and much less informal definition of calibration provided in Part I, adjustment is not mentioned anywhere. It simply describes how calibration is a system of comparison.

This is because calibration and adjustment are two separate things and should always be viewed as such

Adjustment In Action

Unfortunately, the actual adjustment of a scale is not in the scope of this article. However, as you might imagine, you will always want to recheck (re-calibrate) the scale after the adjustment. After all, you will want to make sure that you adjusted it all the way back to where it should be reading.

Using the formal definitions, this sequence looks like this:

  1. Calibration
  2. Adjustment
  3. Calibration

This process would need to be completed until the scale is adjusted correctly.

While this may seem like an unnecessary breakdown to make, it is an important one. Remember, calibration does not account for adjustment, whatsoever. Any time an adjustment takes place in the calibration process, a second calibration must occur.

You will, of course, note that there are technically two different calibration findings in this scenario. The first one, before adjustment, is commonly called the "As Found" reading. The second, after adjustment, is commonly called the "As Left" reading. These two separate findings are very important, because you need to know just how far something was out of tolerance before the adjustment occurred. Always make sure your calibration provider is giving you this information. At Fox Valley Metrology, we provide this information with every measurement we take. Please see our sample certificate for an example.

Hopefully, this is a fairly easy differentiation to make. However, in the quality industry, the lines are often blurred. Many people tend to see this as an all-in-one process. Although an adjusted gage has the same outcome as a gage that passed calibration the first time, it is important to remember the distinction between the two.

In Part III, we will explore some of the underlying theories and principles that affect the calibration process and why this matters to you.

About the author

Steve Toll

Steve has been around the calibration industry his whole life. His father, Mark Toll, founded Fox Valley Metrology in 1996, when Steve was only 6 years old. Steven went on to graduate from Milwaukee School of Engineering, one of the most challenging and accolated technical universities in the country. This lifelong immersion in the industry has led him to become the Vice President of Sales for Fox Valley Metrology since 2014.

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