Chapter 1
What is a calibration cycle?
The calibration cycle is the interval at which a measuring instrument is calibrated. It serves as a standard for managing the timing of the next calibration in order to periodically check whether the measuring instrument is maintaining the required accuracy.
The date of issuance of the calibration certificate and the date of the next calibration are different.
A calibration certificate is a record showing the condition of the measuring instrument at the time of calibration and the calibration results. There is no fixed validity period set for the certificate itself.
Therefore, the timing of the next calibration must be determined by the company itself, based on how the measuring instrument is used and its management requirements.
According to NITE's JCSS FAQ, there is no expiration date for JCSS calibration certificates, and recalibration should be considered by the user based on factors such as the frequency and environment of use of the measuring instrument.
Calibration, inspection, and adjustment have different roles.
| Item | Role | Points to look at |
|---|---|---|
| Calibration | Check the difference between the measured indicated value | display value, difference, uncertainty, calibration result |
| Inspection | Check if it is working correctly. | Appearance, operation, presence of abnormalities |
| Adjustment | Adjust display and output as needed. | Condition before and after adjustment, and whether recalibration is necessary. |
It's important to consider each step separately: first, check the current state through calibration, and then, based on the results, determine whether adjustment, repair, or replacement is necessary.
Chapter 2
Why do people struggle to set calibration cycles?
The calibration cycle must be determined while ensuring the reliability of the measured values, and also considering the costs and burdens associated with calibration, such as equipment downtime.
Making the cycle too short
The increased frequency of calibration will lead to increased costs, the burden of removing measuring instruments, and the preparation of alternative equipment.
Make the cycle too long
The time it takes to notice a change in measurement values may lengthen, potentially leading to the continued use of inaccurate measuring instruments for extended periods.
Unable to explain the basis
Simply stating "it's always been this cycle" makes it difficult to explain the reasoning behind a decision when reviewing the cycle.
When introducing new measuring equipment, one possible approach is to set a provisional calibration cycle based on working conditions and manufacturer information, and then revise it to suit your company's actual situation while accumulating subsequent calibration results.
Chapter 3
Five criteria for determining the calibration cycle
The calibration cycle is not determined by a single factor, but rather by combining multiple perspectives.
| Judgment criteria | Confirm | Way of thinking |
|---|---|---|
| Frequency of use | Do you use it every day, or only when needed? | The more frequently you use something, the more opportunities you need to check for changes. |
| Operating environment | High temperature, high humidity, vibration, dust, dew condensation, etc. | We will check the environmental load on the measuring instrument. |
| Required accuracy | Pass/fail judgment, process control, reference values, etc. | We will confirm the required importance of the measurement values. |
| Past calibration results | Magnitude of error, trend, outliers | We will check the changes in the measuring instrument based on the results so far. |
| Impact | Impact on quality, safety, and process when measurement values are inaccurate | Measuring instruments with a high risk of misalignment are managed with greater care. |
In the case of thermometers and temperature sensors, the way degradation and its impact on measurement manifest differs depending on the type of thermometer, such as thermocouples, resistance thermometer, and radiation thermometer. It is important not to assume that "all thermometers have the same cycle," but to consider working conditions and measurement method separately.
Chapter 4
How to set the calibration cycle for each measuring instrument
When determining calibration cycles, there are limitations to setting a uniform number of years based solely on the type of measuring instrument. Even with the same type of measuring instrument, the required calibration cycle will vary depending on the frequency of use, environment, and required accuracy.
Newly introduced measuring instruments
Based on working conditions, required accuracy, manufacturer information, etc., a provisional calibration cycle is set, and actual calibration results are accumulated.
Measuring instruments that have accumulated historical data
We review the calibration results from multiple calibrations to check whether the error is stable and whether it is changing significantly.
Measuring instruments used in critical process
When measurement values directly impact quality assessment or safety, the period is set with an emphasis on the impact of any deviations.
Measuring instruments used in harsh environments
In environments where measuring instruments are subjected to load, such as high temperatures, vibration, humidity, and chemicals, these factors are taken into consideration.
Rather than fixing the cycle from the start, such as "thermometers every year" or "this measuring instrument every six months," it's better to set an initial maintenance cycle and create a system that allows you to decide whether to maintain, extend, or shorten it based on the calibration results. This approach leads to management that better reflects your company's actual usage.
Chapter 5
Considerations when extending or shortening the calibration cycle
When considering an extension
If past calibration results have been stable and there have been no significant changes in the operating environment or usage methods, this can be used as a basis for considering whether the calibration period can be extended.
When considering shortening
If significant discrepancies are observed, the operating environment becomes more demanding, or the product is used in a critical process, we will consider shortening the cycle.
Check not only the period but also the scope of the impact.
If a significant discrepancy is found during calibration, simply accelerating the next calibration may not be sufficient. It may be necessary to consider whether past measurements using that instrument, and the impact of those measurements on products and process, need to be reviewed.
Chapter 6
Practical workflow for determining the calibration cycle
- We will take stock of the current situation. We will organize the types of measuring instruments, their uses, frequency of use, operating environment, and importance.
- Set the initial cycle. Based on working conditions and manufacturer information, set a cycle that is feasible for your company's operations.
- Record the calibration results. Accumulate calibration results for each measuring instrument to allow for the identification of trends in changes.
- Review the cycle. Check if it is stable, if the deviation is increasing, and if working conditions have changed.
- Record the reasons for your decisions. Keep a record of why you maintained, extended, or shortened the cycle, so that you can explain it later.
By going through this cycle, we can shift from managing things based on "this cycle is customary" to "a cycle determined based on past results and working conditions."
Chapter 7
Things to consider before reviewing the calibration cycle
When reviewing calibration cycles internally or consulting with external parties, organizing the actual usage and past data for each measuring instrument will make the discussions proceed more smoothly.
| Check items | Things to organize |
|---|---|
| Measuring Instrument | Type, model, serial number, measurement range |
| working conditions | Frequency of use, operating environment, installation location, temperature range |
| Calibration results | Results from the most recent few times, trends in deviations, outliers, and whether or not the test was unsuccessful. |
| Required accuracy | Quality assurance, audit compliance, internal standards, customer requirements |
| Impact | Impact on quality, safety, and process when measurement values are inaccurate |
| Certificate Requirements | Calibration certificate, traceability, and JCSS requirements |
Why not review your calibration cycle based on the actual practices of each measuring instrument?
After reviewing working conditions and past calibration results, you can consider how to set the calibration cycle.
Consult about calibrationSummary
The calibration cycle is determined based on the actual usage and past data for each measuring instrument.
Instead of managing calibration cycles with a uniform number of years, it is important to make decisions for each measuring instrument by considering factors such as frequency of use, operating environment, required accuracy, past calibration results, and the impact of deviations in measured values.
By initially setting a provisional cycle and then considering maintaining, extending, or shortening it while accumulating calibration results, you can move closer to a calibration management system that suits your company's working conditions.
FAQ
FAQ
Is there a set number of years for the calibration cycle?
There is no fixed number of years. It is determined for each measuring instrument based on factors such as frequency of use, operating environment, required accuracy, past calibration results, and the impact of deviations in measured values.
If I use JCSS calibration, will the deadline for the next calibration also be set?
No. JCSS calibration certificates do not have an expiration date. NITE states that users should consider recalibration based on factors such as frequency of use and usage environment.
Is it possible to extend the calibration cycle?
If past calibration results have been stable and there have been no significant changes in working conditions, this can be a reason to consider extending the service. It is important to keep a record of the basis for your decision.
What should I do if a large discrepancy is found during calibration?
In addition to adjusting, repairing, or replacing measuring instruments, we also consider whether it's necessary to review past measurements performed using those instruments and the impact of those results on products and process.
Is the calibration cycle for temperature sensors based on the same principle?
While the basic concept is the same, the operating environment and degradation effects differ depending on the type of thermocouple, resistance thermometer, or radiation thermometer. It is important to consider the operating temperature range and installation conditions as well.
