interpolation in calibration what is your opinion on the subject?

[griff61]

You should just stick to meters and scopes....

You overlooked this comment kalibrater
"I was reading some mathematic theory on it and there are a few different solutions they discuss with a whole lot formulas and I lost interest."

[measure]

Regarding the statement about extrapolation, "Additionally, its use would automatically require a limitation be placed on the device being tested since the device could not have been tested to 100% of its range basically rendering the untested portion unusable to most customers anyhow" there are exceptions and notable ones.

For example, the Fluke 792A AC-DC Transfer Standard is a primary-level reference device, yet if you send it to NIST for calibration, their cal report contains many points that were determined by extrapolation - even NIST does not test every point - several are determined by extrapolation. The extrapolated AC-DC difference data is valid and usable. In this case, the "limitation" is a slightly looser calibration uncertainty for the extrapolated points over those that were directly measured. You see, the 792A performance is so very stable and predictable, even though it contains active circuitry, that its performance from a relative few measured points is sufficient to extrapolate the others, once adequate data supporting the device's long-term stability is established. (There are published papers available regarding this performance aspect of the 792A.)

I admit instances such as these are relatively few, but they do exist.

[CalibratorJ]

even NIST does not test every point

Don't tell NIST that, not if you want to stay one of their customers and/or in their good graces. But, no, they do not measure every point, specifically, 290 degrees Kelvin comes to mind right off the top of my head.

All of the "big box" companies are getting really good at manufacturing specifications but forgetting to manufacturer devices that are actually capable of meeting those stated specifications after a year or two *cough* LPN *cough* LPNX.

Anyway, back to the pressure chart recorder, if those are the points the customer wants checked specifically, and they are paying for the cal, and the cert states those points, then what's the problem? After all, calibration is a customer service business. You don't take care of your customers and give them what they want, then they will find someone who does (unless they can't due to various restrictions ie DOD, contract, etc).

[griff61]

You don't take care of your customers and give them what they want, then they will find someone who does (unless they can't due to various restrictions ie DOD, contract, etc).

Very true, I would add that even many DoD customers can find a way to get their support elsewhere.

[Duckbutta]

My opinion? Interpolation is an accepted calibration practice. It's a staple actually, and anyone that doesn't know that probably shouldn't be calibrating anything. They obviously aren't qualified.

[griff61]

My opinion? Interpolation is an accepted calibration practice. It's a staple actually, and anyone that doesn't know that probably shouldn't be calibrating anything. They obviously aren't qualified.

But reading is hard