Precautions for use of instruments so as to avoid in accuracy in measurements-reliability

Precautions for use of instruments so as to avoid in accuracy in measurements-reliability 


Proper use and care of precision measuring tools is very important if accuracy and reliability are to be maintained.  

Here are some guidelines to follow much of which is just common sense.

1. Measuring a work piece (on a lathe) should be carried out only after the work piece has stopped moving; otherwise, there could be wear on the measuring faces and the accuracy of the tool may be compromised.

2. Wipe the measuring faces of a precision measuring tool and the to-be-measured surface of the work piece to prevent the measuring accuracy from being negatively affected by dirt or dust. 

It is not advisable to use a precision tool such as a vernier caliper, micrometer or dial indicator to measure forged roughcasts or abrasive-bearing pieces, i.e. carborundum, because the measuring faces will be abraded and accuracy will diminish.

3. Never put precision measuring tools together with hand tools, such as cutting tools, files, hammers and drills for the fear of bumping and damaging the precision measuring tools. 

Never leave them on a lathe or other running machinery for fear of vibration causing them to fall to the floor.

4. Precision measuring tools should not be used as substitutes for other tools.
 
Don’t use a caliper as a screwdriver!  

Don’t use a micrometer as a hammer.

5. Temperature has a substantial impact on the measuring results. 
Precision measuring tools should not be put under direct sunshine or any other heat source because accurate measurements will not be achieved as the temperature increases.

6. Precision measuring tools should never be put near any magnetic material such as a magnetic worktable, to avoid being magnetized.

7. When having discovered some abnormal phenomena on a precision measuring tool, such as rough surface, burr, rusts, distortion of the body or ineffective movements, users should not be allowed to fix it on their own, not to mention fix it with hammers, files or emery cloth for the fear of augmenting errors. 

Users should send the flawed tool to the repair depot and use it after it is repaired right!

8. Tools should be cleaned after use.  

Perspiration in your hands can be a bit caustic and react slowly with metallic materials so it is a good practice to lightly oil the tools to minimize any chemical reaction that might take place.

Store tools in a dry place.  

Never leave them outdoors.

9. Periodic maintenance should be applied to precision measuring tools.

Long-used precision tools should be sent to authorized calibration facilities periodically for test and calibration to avoid product quality problems caused by unreasonable reading errors of the tools.

Reliability
Reliability is consistency in measurement over repeated measures. Reliable measures are those with low random (chance) errors. Reliability is assessed by one of four methods: retest, alternative-form test, split-halves test, or internal consistency test. Validity is measuring what is intended to be measured.

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