I manage a proficiency test program for calibration labs. This consists of sending an artifact to a laboratory and asking them to measure it, then seeing if their answer is correct, taking measurement uncertainty into account.
One test involves measuring the angle deviation of a pair of fixed optical wedges, one with a nominal 50 arc-second deviation, and the other with a 10-second deviation. This is a fairly simple test, but the calibration procedure they use for the proficiency test is old and specifies obsolete equipment. The idea is that to do the test, they’ll use their more modern equipment, and they will have to adapt the procedure accordingly to make a successful measurement. That is, they’ll have to understand what they’re doing, rather than just blindly follow a step-by-step recipe.
That’s the theory, anyway. In practice, it turns out that some labs kept those old museum pieces in the back of the store room and dusted them off to do the proficiency test. “Hey, that’s what the procedure called for...”
The is the autocollimator used for measuring the angle deviation of a pair of fixed optical wedges.
One of the labs running the proficiency test that did this used its approximately forty-year-old manual autocollimator. Its result for the 50-second wedge was right on the money, but for the 10-second wedge, it was way off. I called the lab and talked with the technician. He seemed experienced with the measurement equipment and generally seemed to know what he was doing. I couldn’t find any fault with his technique based on his description. I asked him to send me his raw data.
To do the test according to the procedure, they make five separate runs of the wedge deviation angle measurement, and they average the five results for the final reported value. The readings for the 50-second wedge showed a normal scatter of a few tenths of an arc-second in the readings, but for the 10-second wedge, the readings were all over the place!
They varied by a couple of seconds or so. There isn’t much that can go wrong with a fixed optical wedge, which is one of the reasons it makes a good proficiency test artifact. It’s just a piece of glass with an angle between its two aperture faces, mounted in a metal frame. I asked him to check if the wedge prism had come loose in its holding cell. To cause this much variation, it should be rattling like something you’d give a baby to play with. He reported back, “No, it’s solid as a rock.”
With so many advances having been made on nearly every level in engineering, manufacturing, and testing, I find it scary that a 40-plus year piece of equipment still plays such a major role in development. Semi-proficient or not, it's time to get with the program and embrace the modern world.
Beth: I agree with you for 80% of the cases out there concerning aging equipment. However the other 20% I will have to disagree.
One of the problems will show itself when you have custom application or device that was designed by the current Guru who then, 5 years later, retires and never really taught anyone some of their tricks. This tends to leave a company/group with a piece of equipment that was built in house that still does not have a modern counterpart because it was never designed for the outside world.
We have several issue like this at work where it is taking longer to try and recreate a test solution than if we had just continued using the solution that was made 5 or 10 years ago.
Good distinction, Jason. And you bring up an important issue I keep hearing about--that is the knowledge transfer of critical IP, especially when a firm has not fully embraced systems and processes to capture all of their design intellectual property. Whether that IP sits in some engineer's head regarding test practices or design best practices, it's crucial organizations formalize a way to hang on to all those IP assets especially as we see a generation of engineers retiring from the work force.
I can't totally fault them for using old equipment, as long as it was working well. In the physical/dimensional arena, there are many areas where the advances in engineering have not greatly improved measurement accuracy.
For example, modern electronic theodolites are no more accurate in terms of angular measurements than manual instruments that are older than I am, and I can retire in a few years. The modern instruments have additional features, are easier to read and operate, but are no more accurate than some theodolites built in 1950. This ease of use comes at a price. The old manual instruments had to be made carefully, and got their accuracy by the manufacturers making the instrument misalignments as small as possible. Modern instruments measure the misalignments and compensate for them in software. This works great, as long as the instrument was setup properly. Otherwise, it will cheefully lie to you with a straight face.
Mechanically and optically, those old theodolites are often better than the new ones. That is, and this is the kicker, assuming they have been carefully used and maintained for all those years.
- Company's knowledge base in it's employees (a very hard to quantify item)
- Standards (and equipment in general) being used in a organization.
I thought the Rob did a good job of making the distinction. Jason and Tim made some very good points on the subject. Properly maintained older equipment in knowledgeable hands often performs as well (sometimes much better than) the latest / greatest equipment available.
The wisdom to know which issue you are dealing with ... priceless.
sorta like: defining the most cost effective duration to own a car. It depends.
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