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# ISO/IEC 17025:2017 Webinar Questions & Answers

Industrial Measurements
Life Science

We recently had a webinar on the 2017 revision to ISO/IEC 17025. You can watch the webinar recording and get the presentation PDF now.

During and after the webinar, we received questions from participants; many questions were about TUR - Test Uncertainty Ratio. We have a separate blog related to this topic, and the answers to the other questions that came from the webinar below.

### A Question on Test Uncertainty Ratio:

It is understood that in %RH and dew point calibration, the rule of 4:1 test uncertainty ratio (TUR) is rarely achieved. This is true even at the level of NIST/PTB/NPL when transferring their uncertainty to our chilled mirror. How do you incorporate this in your calibration process?

In humidity, that 4:1 TUR can be hard to get, particularly when you are calibrating high-accuracy instruments. The change in 17025 in 2017 was that decision rules need to be agreed upon before the calibration. One approach is to use guard-banding and calculate a new acceptance limit from the accuracy specification and the measurement uncertainty. The 4:1 TUR gives you an expected rate of false accepts. You can use guard bands as part of your conformance decision to bring the probability of false accept down to what you would get in a situation where you had achieved a 4:1 TUR.

### Another Question:

Due to limited TUR ratio (between the lab declared CMC and the unit under calibration), what will be the risk assessment and how to approach to mitigate this situation?

We look at what the severity of a failure would be, and/or what that instrument is used for. Things like how often it is calibrated or what is the history of the instrument in terms of its previous calibrations, its stability and drift over time to get an idea of its probability of failure. If you have something that drifts and doesn't get checked often and is part of a critical process then that would be classified as a high risk instrument that you would want to take action on. Maybe your best course of action is to decrease the calibration interval, or get an accredited calibration, or use a tighter conformance decision.

## Regarding ISO17025 vs 9001, but what if I need a NIST calibration?

While you can get your instrument calibrated directly by NIST, in most cases people use the term NIST calibration to mean one that is NIST traceable. Traceability means that there is an unbroken chain of comparisons relating an instrument’s measurements to the International System (SI). NIST is one source for the top of the chain, as are other national metrological institutes such as NPL in the UK. Both 9001 compliant and 17025 accredited calibrations can, and in most cases will, be traceable.

We have an article called: "The Tracks of Traceability" in this white paper on Metrology.

## Why would you ever not want a conformance decision?

It is up the customer and their quality system. A conformance decision is an interpretation of the reported calibration results. The impact of a measurement error depends on how you are using the instrument. For example, pre-calibration you may use a reference in two applications with different process tolerances. In this case, you might want the flexibility of not having a conformance decision that only applied to one context.

We have a blog on tolerances called Instrument Tolerances: Manufacturer vs. Process

## Should I perform a risk assessment every time I make a procedural change?

Yes. It is a great tool, and unless is it a major change, it does not need to be an involved process. It is a normal part of any quality management system for a change to a procedure or piece of equipment to trigger some sort of change control process. Risk analysis is already an implicit part of most change control processes. One common implicit risk assessment is to have more change controls when a critical process is affected. Matching your actions to the severity level of possible failures is what risk assessment is all about. If you have previously done a risk assessment for the procedure that is changing, all you need to do is consider if the change affects any scores and update accordingly.

## How do we check between calibrations for a chamber controlling temperature & humidity?

The answer varies depending on the importance of the instrument to your process. Here is where risk analyses comes into play. The results of your analysis will help determine how involved the check should be. In many cases, a one-point spot check could suffice. Basically you should have regular readings from a stable check instrument to detect any drift.  Below we have a video on how to perform one-point in-situ calibration and adjustment for the Vaisala HMT330 using a Vaisala HM70.

## Calibration and Repair Services

Calibration is essential for all measurement instruments. Using Vaisala’s calibration services is a quick and a stress-free way of taking care of regular calibration and it gives you several other benefits as well. We don’t just calibrate your products, we also adjust them, test their functionality as well as clean and replace wearing parts when needed.

You will also get a clear report with “as-is” and “as-left” values and a certificate to guarantee that the accuracy and traceability of your instrument complies to industry recognized standards.

To enhance your calibration service, we recommend choosing our Premium or Calibration Care agreement that cover calibration for several years. If preferred, each calibration can also be ordered separately via our Online Store. Please visit the On​line Store to check the availability in your country and to place your order 24/7/365.

## Comment

### Rocio Sánchez Navarro

Jul 25, 2018
quisiera saber el idioma en el que se dara

### Tiina Kiianlehto

Jul 25, 2018
The webinar and the presentation document are in English