Suitability of Instruments

Suitability of Instruments

Presented by

Better by Your Every Measure • 800.828.1470 • www.transcat.com

especially for

Nashville July 2013

Perhaps an attorney evaluating a case to see if it’s feasible to accept . . .

or maybe this . . .

. . . no, neither of these is the definition I’m looking for . . .

What is “Suitability”?

• “Each manufacturer shall ensure that all inspection, measuring, and test equipment, including mechanical, automated, or electronic inspection and test equipment, is suitable for its intended purposes and is capable of producing valid results.”(21 CFR 820.72).

. . . while this is the right context of suitability, it still remains undefined.

What is Suitability?

Suitable for intended purposeLet’s start out with a simple example . . .

a) What is the most suitable tool for the job?b) Which have you never used to drive a nail?

Suitable for intended purpose

Really – you’d use a hammer on a screw??Suitability means using the right tool for the job …… and using it the right way!

Who said the Hammer is the right tool for this job?

1. Understand components of Suitability for instruments2. Formulate your own definition of Suitability3. Compare to your organization’s current definition

• Create definition for your organization if one doesn’t exist• Enhance definition for your organization if one already exists

Learning Objectives

Reasons People Use the Wrong Tool1. Inconvenient; don’t want to go get the right tool2. Don’t know how to use the right tool/instrument3. Don’t own the right tool/instrument4. Can’t afford the right tool/instrument

Simple vs. Complex Process• These are simple hand tool examples• If it’s this easy for people to use the wrong tool (or the right tool

the wrong way) in a simple process . . .

Simple vs. Complex Process• . . . what are the chances of introducing errors when using more

complex tools/instruments in more complex processes?

Measurement Quality Assurance• Metrological Traceability is important, but . . .• It means nothing if the industrial processes don’t maintain a good

measurement quality assurance program• MQA is critical to industrial manufacturing processes:

– To keep product costs at a minimum– To maintain safety for employees and product consumers– To keep product lead times from being delayed– To make the traceability chain a worthwhile effort (and its costs)

Where does Risk Creep into Your Process?Measurement Quality Assurance encompasses a number of assumptions within a manufacturing process:

1. Product Acceptance You made the right decision about the acceptance or rejection of your product (or a component of your product) during the manufacturing and quality acceptance process.

2. Basis of Decision The decision was based (partially or completely) on quantitative information provided by one or more measuring instruments.

3. Suitability for Intended Purpose

You made the right choice in selecting instrument(s) that are appropriate for the measurements in your process.

4. Instrument Application The instrument(s) were used correctly in the manufacturing process when making decisions about product quality.

Where does Risk Creep into Your Process?Measurement Assurance encompasses a number of assumptions (con’t):5. Beginning of Period

ReliabilityThe calibration of the instrument prior to your decision about the product indicated it met its performance expectations.

6. End of Period Reliability

The subsequent calibration of the instrument following your decision about the product indicates that it continues to meet its performance expectations.

7. Calibration Process Calibrations are executed correctly and support the application(s).8. Non-Conformance

Review (NCR)If a calibration indicates that the instrument failed to meet its performance expectations, your quality system reviewed any impact to the decision(s) made about your product(s) that were based on the quantitative values presented by the instrument.

9. NCR Accuracy This impact study was thorough, followed an unbiased, forensic approach, and did not miss the mark on determining any detrimental affect on product.

10. Risk mitigation Any negative result from the impact study was properly mitigated to remove or reduce product risk.

Example: Module transfer process between a space vehicle and the International Space Station (ISS). Heaters prevent ice buildup in the transfer module and spacesuits (Space Suit UP!), specifically in the gloves and helmet camera. The main battery pack provides 12.5 ±1.5 VDC

– Helmet camera heater requires 12 ± 1 VDC– Glove heaters provide a resistance of 57.7 ± 2.9 Ω; require 9 ± 0.5 VDC

Note: No matter how simple the process, following a consistent procedure will keep you from making ‘honest mistakes’ that end up wasting time/money or that cause safety issues.

Step 1: Determine all measurements that will be made in this process• VDC: 12.5, 12, 9• Resistance (Ω): 57.7


Example: Module transfer process between a space vehicle and the International Space Station (ISS). Measuring heater voltage and resistance.

Step 2: Determine initial list of instruments for consideration• Centech 37772 Handheld DMM• Fluke 87V Handheld DMM• Agilent 34401A Benchtop DMM• Agilent 3458A Opt 002 8.5 Digit Multimeter



Step 3: Collect the OEM specifications for all instruments• Centech 37772



Step 3: Collect the OEM specifications for all instruments• Fluke 87V



Step 3: Collect the OEM specifications for all instruments• Agilent 34401A



Step 3: Collect the OEM specifications for all instruments• Agilent 3458A Opt 002



Step 4: Evaluate instruments for Suitabilitya) Parameter Verification: Determine if the selected instruments cover the

parameters of interest

• In this case, all four instruments can measure both parameters: DC Voltage and DC Resistance



Step 4: Evaluate instruments for Suitabilityb) Range Verification: Determine if the selected instruments have ranges

that cover the target measurements– DC Voltage: 9V, 12V, 12.5 V

• Centech 37772: The 20V range covers all of the target measurements• Fluke 87V: The 60V range covers all of the target measurements• Agilent 34401A: The 10V range covers the 9V measurement; 100V range covers

other voltages• Agilent 3458A: The 10V range covers the 9V measurement; 100V range covers

other voltages– Resistance: 57.7 Ω

• Agilent 3458A: The second lowest range covers the resistance measurement• All other models: The lowest range covers the resistance measurement



Step 4: Evaluate instruments for Suitabilityc) Accuracy/Resolution Verification: Using the accuracy statement of each

instrument, convert to a tolerance in the engineering unit of the measurand.

Centech 37772: Measure 12.5 VDC on the 20V rangeAccuracy (20V range): ±(0.5% of rdg + 1 digit); resolution is 10mV on this range

Tolerance = ±(0.5% x 12.5V + 10 mV)= ±0.0725 V= ±0.07 V (considering resolution)



Step 4: Evaluate instruments for Suitabilityc) Accuracy/Resolution Verification: Repeat for all other measurements

and instruments.



Step 4: Evaluate instruments for Suitabilityd) Process Accuracy Ratio (PAR) Calculation: Use the following formula to

calculate PAR for each measurement and each instrument.

where:UPL = Upper Process LimitLPL = Lower Process LimitUIL = Upper Instrument LimitLIL = Lower Instrument Limit



Step 4: Evaluate instruments for Suitabilityd) Process Accuracy Ratio (PAR) Calculation: Use the following formula to

calculate PAR for each measurement and each instrument.Centech 37772 for the 57.7 Ω process measurement:



Step 4: Evaluate instruments for Suitabilityd) PAR Calculation: Repeat for all measurements and instruments.



Step 5: Intended use: other applications?If you believe the selected instrument may be used in other applications, you must perform this same procedure to determine suitability of the instrument for those applications.



Step 5: Cost FactorCentech 37772: $20PAR: One at 3.6:1Others > 8:1

Fluke 87V: $400PAR: All > 9:1

Agilent 34401A: $1kPAR: All > 300:1

Agilent 3458A: $9kPAR: All > 2000:1


One more thought . . .

After you become comfortable with this Suitability process and calculating PAR, you really should consider taking it a step further . . .

Process Uncertainty Ratio (PUR): Takes into consideration other errors being introduced while making process measurements which include:• Operator training• Gage Repeatability & Reproducibility (Gage R&R) variations• Environment in which the instrument is being used• Storage conditions for the instrument when not in use• Handling conditions for the instrument over its calibration interval

These will be touched upon in the other two presentations.


• In the end, running your business is not only about international, federal, customer, or internal requirements, policies, or procedures – it’s about making a safe, reliable, superior product that fills a need/desire in the market place and is profitable for your company.

• Measurement Quality Assurance should be designed to help you minimize risks in your decision making process about your product’s safety and quality.

• Suitability of Instruments is a key part of guaranteeing good measurements!• Too often MQA is not fully implemented (all 10 categories), causing the

reliability of your Measurement Quality Assurance Program to lose value and become ineffective.

• If you’re going to put the effort and money into only some parts of this program, or you simply do not recognize all of the factors, it will likely cost you elsewhere through rework, recall, or consumer perceptions.

• Make your Measurement Quality Assurance Program robust so that it works for you to keep cost and safety issues to a minimum and profits up!

Measurement Quality Assurance/Risk

Thank you for attending!

800.828.1470www.transcat.com

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Suitability of Instruments