Archive for the “Measurement QA” Category

Original Article dated: Dec 17, 2008 By: G. Raymond Peacock, Temperatures.com Inc.

During the past year, I’ve been discussing some of the best practices required to successfully add a new sensor to your operations. This month, I’ll examine the next to the last step in the process: commissioning the sensor. In this phase, you’re simply ensuring the sensing device is functioning and will continue to do so for an appropriate length of time.

Covering All the Bases
All too often, this step is overlooked, even though it is a key part of the installation process. The challenge here is that there are no universally accepted guidelines to follow.

So I’ll review seven steps that have served me well over the years. The essential tasks involved in commissioning a sensor can be summarized as follows:
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images-cbThis eighth essay in a series on Sensorsmag.com. It is reproduced here with permission of SensorsMag a Questex Media Group, Inc. publication. The format has been slightly changed to make it easier to read online.

Jul 22, 2008 – by: G. Raymond Peacock, Temperatures.com Inc. – Sensors

This is the eighth essay in a series expanding on an article I wrote for Sensors titled “A Twelve-Step Sensor Selection Checklist.” In May, I talked about the process of soliciting bids. This month, I’ll focus on acquiring a sensor, or measurement device, and expert technical services.

A Source of Expertise
Keep in mind, the sensor supplier is an expert in the sensing area in which you are involved and a valuable technical resource, regardless of your own level of experience.
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image-uncertThis is the fifth essay in a series expanding on an article I wrote for Sensors (Sensorsmag.com) titled “A Twelve-Step Sensor Selection Checklist.” .
(Note: It has been modified very slightly to make it more easily read in this format)

This month, I’ll look at the phase of the sensor selection process in which you review your error analysis. In this step, you decide if a particular sensor meets your measurement requirements.

Some people balk at doing detailed analysis, saying it’s unnecessary.

Others will want to just try a sensor and see how it works.

In most cases, the analysis approach beats the cut-and-try method hands down. You’ve come this far. Don’t waste the effort.

Be Prepared
In this analysis, you estimate the likely errors encountered with a sensor. Essentially, you answer the question: How close will this choice come to meeting my measurement requirements?

Believe me, the analysis is worth doing and documenting. Someone always questions your choice. So have your answer ready.

The review can be difficult and lengthy and may require some serious modeling—using Finite Element methods or other analytical techniques—to get to a realistic appraisal of likely results. Remember, however you arrive at your estimate, realize that it is but one component in the calculation of measurement uncertainty.

In the overall process, you must include all the components in the total measurement uncertainly calculation, combining calibration uncertainties and those due to influencing factors such as varying ambient temperature and other conditions.
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Dr. Deming at JUSE in 1982 {Image Courtesy The Deming Institute}

Dr. Deming at JUSE in 1982 {Image Courtesy The Deming Institute}

The teachings and experiences of W. Edwards Deming slowly took hold in my learning as I worked for a USA Steel Company in Ohio in the 1980s and ’90s. I knew little about Quality Assurance when I first joined the orgainzation, but got involved in their system of Statistical Process Control, that had been dubbed with their own name: “Integrated Process Control” or IPC.

Every corporate employee was given a copy of Massaki Imai’s book KAIZEN – The key to Japan’s Competitive Edge (Random House Business Division, NY, NY, 1986) and introduced to IPC through required classes on it taught by consultants from the noted QA educational Group, Tennessee Associates. It was quite an eye-opening experience for me and I still have all the books and manuals.

The work of Deming and Juran after World War II helping Japan rebuild their manufacturing industries was brought to my attention. I learned a lot and looked further into Deming’s works. I not sure I went totally into them, but I went far enough to appreciate their worth.
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