Calibration of a Digital Vernier - Need to check/calibrate/validate all 3 functions?

V

Van_H

#1
Good Afternoon, I am about to calibrate a Mitutoyo digital vernier of 12", with the 3 function inside measurement, outside measurement, and depth; my question is this, do i need to check, calibrate and/or validate all of this 3 functions? if so do i really need to buy the standard to check the inside measure?.

Thanks :bigwave: hope you guys can help, Im just starting with this calibration thing.
 
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J

joshua_sx1

#3
Re: Calibration of a Digital Vernier - Need to check/calibrate/validate all 3 functio

...just :2cents: thoughts... I believe, you have to inquire from your supplier of the calibration procedure for that measuring devices – this is the normal approach… if they cannot provide you (which makes them incompetent supplier, for me OK), then you’ll have to go on next option, which is defining your calibration requirements i.e. whether it is going to be in-house or you are going to need a third party calibration agency, and if it in-house, you have to identify whether you need another instrument to calibrate it, you’ll have to define the acceptable parameters including the methodology of your calibration process, the frequency of required calibration (calibration plan), monitoring, the competent of the person who is going to perform the calibration, maintain records of calibration, and so on… and that is only for in-house, now if we are going to external, there would a lot of requirements also needs to fulfill…

...or you can adopt suggestions on calibration procedure posted on this forum, but you’ll have to keep on your mind that there are certain calibrations that are not generic in approach… and your auditor may ask of how do you know that it is the right calibration procedure?

…and again, to make your life easier, go back to your supplier and ask them about the required calibration of that instrument… it's your right as customer... use it!
 
#4
Re: Calibration of a Digital Vernier - Need to check/calibrate/validate all 3 functio

We calibrated external jaws, internal jaws, depth rod and step parameters of the calliper, depending on the model. BS887 gives the minimum requirements for calibration, but it's at you discretion if you do more!
If you want a copy of my procedure, please PM me.
Regards
Paul
 
Z

zancky

#5
Re: Calibration of a Digital Vernier - Need to check/calibrate/validate all 3 functio

Hi Van_H,
if you wont a standard look at UNI 10699-8 (it is in italian but it works, if You need a translation let me know, I hope my english be enough, no problem with italian)

UNI 10699-8 is the theory, it explain how to control the 3 functions.

now the common sense:

First which accuracy do You need?
Mitutoyo sells caliper at ±0.02mm
I have tested many caliper (digital and not) the real accuracy measuring outside faces (e.g. block gauges) is ±0.01.
More problems if you try to measure cylinders or spheres. As the two faces of the caliper are not perfectly parallel and the moving one can tilt due to clearance, the accuracy is ±0.02 (only with new or perfect caliper may be ±0.01). I have seen new caliper of strange company with an error of ±0.03 measuring outside cylinder diameter.
The inside measurement with caliper is something terrible:mg:
You can check by Yourself trying to measure calibrated rings. First the zero for the two ouside measuring faces is quite always different from the zero of the inside jaws. Second at small diameter there is a big error due to misalignement of the two jaws. therefore if you have to (only if You have to) measure inside diameter You need a reference ring close to the dimension You are checking.
For my company I state that caliper can be used in control only for dimension ±0.1mm but never for internal diameter.
If Your customer will to many calipers and few linear gauges, bore gauges etc he will become nervous. It is better to have a go-nogo gauge then a caliper.

best regards
 
#6
Re: Calibration of a Digital Vernier - Need to check/calibrate/validate all 3 functio

The simple answer is no - if you understand the risk of what you decide.

It has nothing to do with the manufacturer of the equipment or even what a standard says - you have to evaluate the use of the equipment and decide if not having all functions calibrated/verified can get you into trouble!!

It's perfectly acceptable, if not always common practice, to have a 'conditional' calibration situation. For example, some organizations use electrical multi-meters for measuring only volts - that's all they need them for - so why have the equipment calibrated on all other ranges? Ohms, Amps etc. The (wise) organization puts a conditional sticker/label on the equipment saying what has been calibrated.
 

howste

Thaumaturge
Super Moderator
#7
Re: Calibration of a Digital Vernier - Need to check/calibrate/validate all 3 functio

I agree with Andy. The only functions of the calipers that need to be calibrated are the ones used. In a company I used to work for, we never used calipers for depth measurement. In fact we removed the depth rods from most of the calipers so they didn't get in the way when we were doing some common measurements. The ones that weren't removed had a "limited calibration" sticker stating that the depth rod was not calibrated.
 

BradM

Staff member
Admin
#8
Re: Calibration of a Digital Vernier - Need to check/calibrate/validate all 3 functio

...
It's perfectly acceptable, if not always common practice, to have a 'conditional' calibration situation. For example, some organizations use electrical multi-meters for measuring only volts - that's all they need them for - so why have the equipment calibrated on all other ranges? Ohms, Amps etc. The (wise) organization puts a conditional sticker/label on the equipment saying what has been calibrated.
I agree with Andy. The only functions of the calipers that need to be calibrated are the ones used. In a company I used to work for, we never used calipers for depth measurement. In fact we removed the depth rods from most of the calipers so they didn't get in the way when we were doing some common measurements. The ones that weren't removed had a "limited calibration" sticker stating that the depth rod was not calibrated.
Agreed, guys. :agree::agree1:I believe I remember seeing a working paper from Hart Scientific (now with Fluke) stressing the practice of calibrating temperature devices just in the range in which it is used. Reasons:
1) It minimizes the stress of a probe across a huge range
2) No need to address failures and such for a parameter that is not even applicable.
3) It keeps the calibration cost and turn around time down.

Bottom line: If you don't use it for that purpose, why calibrate it?

If you do use those functions with your calipers, then yes, purchase the standards and perform the verifications. Too, hopefully you have procured acceptable gauge blocks and an industry procedure for calibration. Too, you should start to consider developing the appropriate environment for calibration, and proper control/maintenance of the gauge program.
 
P

Phil Fields

#9
Re: Calibration of a Digital Vernier - Need to check/calibrate/validate all 3 functio

All good comments.........just remember to ask "is there a possibility that the depth gauge might be used, and will this have an effect of part quality". If the answer is yes, a decision will need to be made about the product that has potentially been produced out of specification.

Phil
 
Z

zancky

#10
Re: Calibration of a Digital Vernier - Need to check/calibrate/validate all 3 functio

All good comments.........just remember to ask "is there a possibility that the depth gauge might be used, and will this have an effect of part quality". If the answer is yes, a decision will need to be made about the product that has potentially been produced out of specification.

Phil
Yes people try to use whatever you suppose not to be used (expecially old broken personal caliper:frust:during audit).

using caliper as depth gauge means You have to zero each time You pass from outside diameter measure to depth measure :nope: and it may happen that someone forget it even with a calibrated one!

I'm trying to write in each control instrucion which device may be used not by the general name "linear gauge", "bore gauge" but with the unique internal code of each instruments (e.g. "the operator shall use micrometer code A23ZX or micrometer code BV12R measuring diameter XX on part YY").
It takes a lot of time expecially when you have to update instruments list or the instruments are not available at the moment, but it solves a lot discussion and problems (the first: auditor asking "can You show me R&R for this control made by the operator?).

May be I'm quite far from the initial issue but I would like to point out that caliper is so a generic device that it may cause more troubles then benefits in the wrong hand.
 
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