Gage R&R for Digital Multimeter - Part with ripple on voltage

U

UweKoehler

#1
Hello,

I'm looking for help for a special requierment from our customer.
We're forced to do a Gage R&R Analysis on our Automatic Test System.
We measure the output voltage of switching power supply with an electronic load.
The problem is now:
The output voltage of every unit is between 12.375 and 12.44V
But also the ripple (a kind of sinus wave) of ervery unit is about 62mV.

We do not use average measurment for several reasons.
So the measurment is a spot measure somewhere into the ripple.

No we found that the Gage R&R %StudVariation is about 30%.
This is clear to me cause the within-part variation from the part itself is already as the part-to-part variation. This is caused by the ripple.

I have not found many examples for such Gage R&R problems. Most Gage R&R analysis are made for fixed parts.
My part is changing it's behavior for every measurement (varies with about 62mV around its avarage voltage).
Is it possible to do the Gage RR anaylisis on such part?
How can I do and how can I write a rational for the ripple and therefore high %studyvariation?

Thank you in advance for your help
Best Regards

Uwe
 
Elsmar Forum Sponsor

Bev D

Heretical Statistician
Staff member
Super Moderator
#2
Re: Gage R&R for Digital Mulitmeter - Part with ripple on voltage

Fortunately, 'most' GR&Rs are not performed on 'fixed parts'...unfortunately however, most common articles and readily accessable or widely published standards and/or guidance rarely deal with any thing other than 'fixed' parts.

In this case of a 'dynamic' characteristic you have two sources of 'measurement error/ to deal with. You have the repeatability of your gage AND the natural and continual variation of the characteristic you are measuring.

If your customer is looking for an indication of the measurement system's ability to properly accept and reject units, you would need to assess both of these components vs the specification, particularly if the process variation (unit to unit) is close to the specification.

If the Customer is only looking for the repeatability of the gage itself then you would need to measure the voltage at the same point in the ripple each time to taek ou thte ripple component.

I'll take the straightfoward path first
 
U

UweKoehler

#3
Re: Gage R&R for Digital Mulitmeter - Part with ripple on voltage

Hello,

thanks for your answer.
The second option - to measure everytime on the same voltage level - will be very difficult to perform. It would be easier then to measure multiple times and bulid an average.
We want to avoid that for 2 reasons:
1. it will cost more time - the measurement is already performed on different operation points of the unit so this will lead to a significant increase of the test time - wich will increase cost. But from our point of view the measurement is "good enough"
2. we hide the ripple totally in the average measurment. This is not what we want.

The thing is:
The customer spec is:
Output voltage is between 11.8 and 13.4 volts
Test system limits are > 12.31 and < 12.63 (already much smaler)
unit to unit will spread a little in this (12.37 to 12.44) but within-unit measurement to measurement also spreads with a ripple of +-0.031V

Our customer just wants to see a number.
<10% great
<30% acceptable
>30% bad.
We have 4 electronic loads
Now I have one with 27.44%, one with 30.68% one with 31.45% and one with 28.6%

I calculated that in the worst case (alternate measurement on the low and high peak of the ripple) the %StudVar can be already 34% without influence of the gage. This will be additonal.

But the customer just sees the number: >30%!

We use 15 samples, 3 times, 3 Operators (which do not have much influence since it is automatic testing). If I reduce the sample size to 10 or 5 and choose them so that the unit to unit variance is big, the %studVar will be much better!
 
D

debyang

#4
Re: Gage R&R for Digital Mulitmeter - Part with ripple on voltage

Is it acceptable to use an alternative TV, for example, a customer spec as the TV for GRR% calculation?
If so, your GRR% might be reduced to meet the requirements.
 
U

UweKoehler

#5
Sorry,

have some problems in the term "TV".
Might be very stupid but I do not know the meaning.

BR
Uwe
 

bobdoering

Stop X-bar/R Madness!!
Trusted Information Resource
#6
...have some problems in the term "TV".
TV is total variation. Usually it is the total variation presented to the gage r&r study by the samples used. They may or may not represent the total variation of the process over time. When using TV as a factor in the analysis, the assumption is that the it does represent the total variation of the process over time. If it does not, because a wide enough variation has not been collected or generated at the point of the study (new process), then the tolerance (total variation of the process permitted) is used often as an alternative representation of the total variance. The reason it is not preferred is if a smaller-than-tolerance total variation is truly representative of the process, then you want to know how much of that total variation is from the measurement system versus the actual process.
 
G

George Weiss

#7
In some cases we loose the sight of the forest because of the trees.
Your process is reporting a measurement to measurement error of same item tested of +-0.031V with a part spec of 11.8-13.4V,or 12.6+/-0.8VDC. Because of your testing methods the PV uncertainty/repeatability of test is about 4% of spec, not considering other factors. From your presented approximately 30% PV, you have a system variation of 13%.
You have a large PV, which would decrease with measurement averaging. You have expressed that you know this would solve the problem, but do not want to take this action.
In this, as in many cases you have to put a square block into a square hole. Averaging is the obvious expected solution, and rational discussions with another person who is looking for a square block in a square hole will circle the obvious solution.
The R&R process exposes the largest variable in a test process. The customer’s request has to be addressed in relation to product requirements.
If your process has a repeatability of 13% of test specification, then maybe it is ok, and maybe not. The idea of 4:1 test accuracy/uncertainty ratio is pressed if 50% is repeatability.

You mentioned that averaging the measurement would hide the ripple value. If only one measurement is made, the ripple value is also not known. Doing an average, and peak+/- would give the average and ripple. but would increase test time.
You are looking to keep costs down, and the customer is asking for enhanced quality. I would suggest a discussion of the added cost to achieve measurement averaging. Sigma-Six suggests doing it the way the customer wants. Just ask him if he wants the added cost(s)?
 
Last edited by a moderator:

Miner

Forum Moderator
Staff member
Admin
#8
Great post george1weiss!

I want to add some additional thoughts to supplement this:

  1. The first question we should always ask ourselves is: What measure is functionally important? For example, take a locating pin that must fit into a hole with tight clearances. While you could measure a random diameter on both the pin OD and the hole ID, this is not important. What is important is the max OD of the pin and the min ID of the hole. Granted there may be additional important aspects in addition to these, but if these two are out, the parts do not fit. What is functionally important about your measure (max, min, average, peak to peak)? What you are currently measuring is the electrical equivalent of measuring a random pin diameter.
  2. The second question that must be asked is: Does the gauge measure what is important? If the gauge does not measure what is important, the MSA results are irrelevant. Measuring a pin diameter with a %R&R of 5% is meaningless if you are measuring the minimum OD and the pin will not fit the hole.
 
Thread starter Similar threads Forum Replies Date
H How to conduct a Gage R&R (GR&R) on a Digital Multimeter? Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 5
B Do I need to perform Gage R&R on a Digital Temperature & Humidity Gage Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 18
B Digital Torque Meter Gage R&R General Measurement Device and Calibration Topics 4
D Procedure for use of a Digital Indicator and a Height Gage Document Control Systems, Procedures, Forms and Templates 6
A Extent of Gage R&R necessary on two Digital Height Gages Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 1
H GRR (Gage R&R) Study for Digital Temperature Gauge Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 4
O Calibrating a Gage Block In-house with Calibrated Digital Calipers General Measurement Device and Calibration Topics 7
D GRR (Gage R&R) procedure for Mitutoyo Digital Micrometer wanted Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 1
E Digital Height Gauge Gage R&R - Need Advise and Help Quick Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 5
Q Gage Supplier - Need a 72" (min) Digital Read Out LLM for the Shop Floor General Measurement Device and Calibration Topics 2
I What is Gauge Capability? Dial Thickness Gage and Digital Vernier Calipers Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 17
S Need help purchasing a Digital Borematic gage (Mitutoyo was suggested) Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 13
B Stability study- Plastic injection molded parts with fixture gage & digital indicator Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 2
A Gage R&R on Digital indicators & Probes?? Is zeroing the gage prior to use OK? General Measurement Device and Calibration Topics 2
B Gage R&R - Digital Torque Wrenches - 5-50 nM range units Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 12
T Plug Gage Calibration Calibration and Metrology Software and Hardware 1
L Gage R&R TMV Acceptance Criteria Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 4
S MSA for attribute relation gage Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 2
E Zero part to part variation - Gage R&R project Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 15
M Gage R&R and right way to measure Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 16
L Gage RandR on automated equipment. IATF 16949 - Automotive Quality Systems Standard 7
B Gage calibration frequency, ISO and IATF - What are the requirements Calibration Frequency (Interval) 3
D Difference between Test Method Validation and Gage R&R Qualification and Validation (including 21 CFR Part 11) 18
R Determining Uncertainty from Gage R&R Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 1
C Correct Calibration Method for Dial Depth Gage General Measurement Device and Calibration Topics 6
C Gage Block Wringing General Measurement Device and Calibration Topics 3
B Gage R&R with NDC=1 Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 19
S Type 1 Gage R&R or something else? Reliability Analysis - Predictions, Testing and Standards 6
G Should I perform Gage R&R only at the beginning of a new project? Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 6
V Thread Plug Gage Pitch GO Diameter out of spec AQL - Acceptable Quality Level 8
G Gage R&R - Where am I going wrong? Part of a FAIR submission (Aerospace) Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 2
R Gage R&R Excel templates Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 3
K Gage R&R with more than 3 appraisers Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 2
Anerol C Gage R&R Template AIAG 4th Edition IATF 16949 - Automotive Quality Systems Standard 3
T Attributes SPC study - Attributive control (Go gage) Statistical Analysis Tools, Techniques and SPC 5
S Capability or Gage R&R Study for Leak Tester? Reliability Analysis - Predictions, Testing and Standards 15
N % Tolerance - Type 1 study on the gages, then a gage R&R (ANOVA) Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 4
M Definitive answer on Type 1 vs Type 2 vs Type 3 Gage Study Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 0
V Gage Management and Gage R&R Software General Measurement Device and Calibration Topics 1
D Gage R&R Study on Load Cells - Large chemical blending tanks IATF 16949 - Automotive Quality Systems Standard 1
B Minitab Type 1 Gage Study on True Position Question Measurement Uncertainty (MU) 1
S Gage R&R on alloy Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 10
8 Need Help - Runout - Function Gage Inspection, Prints (Drawings), Testing, Sampling and Related Topics 7
L Gage R&R studies for identical Devices - Need to confirm the requirement to perform them Reliability Analysis - Predictions, Testing and Standards 2
G Stab Pin Size For Check Gage Inspection, Prints (Drawings), Testing, Sampling and Related Topics 3
E Functional Gage for TOP applied at RFS Design and Development of Products and Processes 5
F No reproducibility Error in Gage R&R? Reliability Analysis - Predictions, Testing and Standards 4
M Template for Attribute Gage R & R wanted Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 3
G Warning about Deltronic Gage Pins - The "Certification of Accuracy" document General Measurement Device and Calibration Topics 13
A Gage type 1 study on CMM Capability, Accuracy and Stability - Processes, Machines, etc. 2

Similar threads

Top Bottom