Instrument Calibration Intervals: Self-Calibration Accepted?

In summary: Calibration is done to ensure that the instruments are giving accurate and reliable measurements, and traceability ensures that the accuracy and reliability can be verified through a documented chain of comparisons to a known standard. This is why it is often recommended to use a higher accuracy bench DMM to calibrate a hand held DMM, rather than calibrating it oneself with another hand held DMM. It provides a more reliable and traceable calibration. In summary, the calibration interval for lab instruments is typically set at 1 year as a tradeoff between calibrating too often and not enough, as components can age and affect calibration accuracy. Self-calibration is not widely accepted in the industry, as most labs do not have the necessary precision test equipment. Calibration
  • #1
likephysics
636
2
Just out of curiosity why is the calibration interval 1yr for lab instruments like DMM, scope etc.
Why not 2 years.

Also, you use a higher accuracy bench DMM to calibrate a hand held DMM.

Instead of getting calibration done by an outside agency, Why not calibrate the handheld DMM yourself using an already calibrated bench DMM.
I am trying to ask if "self-calibration" is accepted in the industry.
 
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  • #2
  • #3
Calibration is normally done using very high precision signal, voltage , current sources etc ( depending on the instrument being calibrated.
This is why it generally costs lots of money to get signal generators, spectrum analysers, oscilloscopes etc calibrated by a certified calibration lab.

I guess a 1 yr period was chosen as a tradeoff between calibrating too often and not enough
Components can age a lot in 12 months time and cause the calibration to become very poor
and as the instrument gets older the components will likely to age even faster

Instead of getting calibration done by an outside agency, Why not calibrate the handheld DMM yourself using an already calibrated bench DMM.
I am trying to ask if "self-calibration" is accepted in the industry.

generally ... no it wouldn't, very few labs would have the precision test equip as I mentioned above. Any business that owns instruments that need regular calibrating will be required to show proof of an independently done calibration certificate

I'm a certified Trimble service technician and the company I work for I do calibration certificates on optical surveying equip. for our customers. Those customers can be required to produce a cal cert to a project manager that they may be contracting to.

Dave
 
  • #4
likephysics said:
Just out of curiosity why is the calibration interval 1yr for lab instruments like DMM, scope etc.
Why not 2 years.

Also, you use a higher accuracy bench DMM to calibrate a hand held DMM.

Instead of getting calibration done by an outside agency, Why not calibrate the handheld DMM yourself using an already calibrated bench DMM.
I am trying to ask if "self-calibration" is accepted in the industry.

It depends upon what 'the industry' needs, for a particular application. It has to depend on the particular circumstances. Sometimes, it is quite sufficient to check that results from two locally available instruments agree to within the particular required limits. You wouldn't often need to check the Mains Volts to 0.1% accuracy, for instance.
 
  • #5
Equipment calibration is a huge issue when it comes to the Food & Drug Administration.

http://www.fda.gov/ScienceResearch/FieldScience/LaboratoryManual/ucm171880.htm

This procedure specifies the schedule and requirements for maintenance, performance, calibration, and verification of laboratory testing equipment. Meeting the criteria in this procedure demonstrates control of the maintenance and calibration parameters needed to achieve the accuracy of instruments used for analytical testing.

http://www.fda.gov/ScienceResearch/FieldScience/ucm171821.htm

The program for calibration of equipment demands that calibrations and measurements made by the laboratory are traceable to the International System of Units.
 
  • #6
sophiecentaur said:
It depends upon what 'the industry' needs, for a particular application. It has to depend on the particular circumstances. Sometimes, it is quite sufficient to check that results from two locally available instruments agree to within the particular required limits. You wouldn't often need to check the Mains Volts to 0.1% accuracy, for instance.

Yes.

I was the calibration technician for a manufacturing facility a few decades ago. I did calibrations for electrical test instruments including voltmeters, wattmeters, power analyzers and many more. We had what we called the "in house standards", which were only used for calibrating the other instruments. The "in house standards" were generally of higher stability and accuracy than the normally used instruments. They "the in house standards" were calibrated once every six months by an outside agency. Or it may have been once a year for some instruments. My memory fails me. A calibration certificate was also issued by the outside agency for proof of traceability for each "in house standard". The frequency of calibration for the instruments used in manufacturing varied, but most of them were every month. A log was maintained for each manufacturing instrument and a sticker was placed on it after it was checked.

However, like sophiecentaur said, all of this may vary depending on the industry. The most important thing, and the thing that most all industries will have in common, is the traceability requirement.
 

1. What is instrument calibration and why is it important?

Instrument calibration is a process of checking and adjusting the accuracy of an instrument by comparing its measurements to a known standard. It is important because it ensures that the instrument is giving accurate and reliable results, which is essential for making informed decisions and maintaining quality control.

2. How often should instruments be calibrated?

The frequency of instrument calibration depends on several factors, including the type of instrument, its intended use, and the environment in which it is used. Generally, instruments should be calibrated at regular intervals to ensure accuracy and precision. Self-calibration is an accepted method for frequent checks, but a full calibration by a certified technician should be done annually or as recommended by the manufacturer.

3. What is self-calibration and how does it work?

Self-calibration is a method where the instrument itself is used to calibrate its own measurements. This is done by comparing the instrument's readings to a known standard and making adjustments accordingly. Self-calibration is typically done in between full calibrations to ensure the instrument's accuracy is maintained.

4. Can self-calibration be used for all types of instruments?

Self-calibration can be used for most types of instruments, but it is not suitable for all. Some highly accurate or specialized instruments may require calibration by a certified technician. It is important to consult the manufacturer's instructions and recommendations for proper calibration methods.

5. How can I ensure the accuracy of self-calibration?

To ensure the accuracy of self-calibration, it is important to follow the manufacturer's instructions and use a known standard for comparison. It is also recommended to perform regular full calibrations by a certified technician to verify the accuracy of self-calibration and make any necessary adjustments. Additionally, it is important to properly maintain and handle the instrument to ensure accurate results.

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