How to Determine the Calibration Cycle for a Handheld Spectrometer Alloy Analyzer?

How is the calibration cycle explained in the standard documents?

The CNAS-CL01 section 5.10.4.4 Calibration Certificate (or Calibration Label) should not include recommendations for calibration intervals unless agreed upon with the client. This requirement may be superseded by regulations.

明确规定 calibration laboratories cannot recommend calibration cycles. Calibration cycles are determined independently by the laboratory based on the actual usage of the measuring instruments, adhering to the principles of science, economy, and accurate value.

The handheld spectrometer alloy analyzer, after the first calibration, the second calibration is initially scheduled for 1 year. If it still maintains accuracy (within the error range compared to the first calibration) after 1 year and is sent to the calibration laboratory for recalibration, it can be extended to 2 years. This pattern continues; however, the recalibration period should not exceed 5 years. During this time, periodic checks must be arranged. If any instability is detected, recalibration is required.

The determination of calibration cycles must be well-founded and justified.

Firstly, let's discuss the calibration cycle, also known as the confirmation interval. It is a crucial element in assessing the quality of metrological work, directly impacting the pass rate of handheld spectral analyzers used for alloy analysis. Strict adherence to the calibration cycle is essential for the smooth operation of scientific research and production activities. To ensure the accuracy and reliability of measured values, it is imperative to scientifically determine the calibration cycle.

What are the consequences of an unreasonable calibration cycle?

Over time, determining whether the calibration cycle for portable spectral alloy analyzers is reasonable depends on the pass rate of calibration and the historical calibration records of the portable spectral alloy analyzer, which can serve as a relatively basic basis. However, changes over time, shifts in operating conditions, or alterations in the methods and conditions of using the portable spectral alloy analyzer may lead to inaccuracies.

Therefore, when the calibration cycle of a handheld spectrometer alloy analyzer reaches its end, it should be calibrated immediately. Additionally, the deviation status of the handheld spectrometer alloy analyzer should be periodically inspected within the valid calibration period. Adjust the calibration cycle appropriately based on the above information, extending or shortening it as needed.

Article II: Principles for Determining Calibration Cycles

Determining the calibration cycle must adhere to two opposing fundamental principles:

During this cycle, the risk of allowable error in the portable spectrometer alloy analyzer is kept as small as possible.

Secondly, it ensures economic feasibility, minimizing calibration costs as much as possible.

To achieve a more balanced value between the aforementioned risks and costs, a scientific approach must be employed, accumulating a substantial amount of experimental data, which is then analyzed and determined.

Do you have to calibrate according to the specified cycle in the calibration procedure?

User usage varies greatly. It's challenging to ensure that all portable spectrometers and alloy analyzers are qualified within their calibration cycles if they are calibrated uniformly and mechanically according to the specified intervals in the calibration procedures. Therefore, it's necessary to determine the calibration cycle based on the actual usage of the portable spectrometers and alloy analyzers. However, due to the complexity of real-world situations, accurately determining the calibration cycle is difficult. We can only aim for a generally correct and reasonable approach, making the actual situation more improved, scientific, and economically sound.

Note:

Rushing to shorten the calibration cycle盲目ly can lead to a waste of social resources and negatively impact the lifespan, accuracy, and production and labor associated with portable spectrometer alloy analyzers. Additionally, extending the calibration cycle solely due to a lack of funds or personnel can be extremely dangerous, as it may result in significant risks, even severe consequences, from using inaccurately calibrated portable spectrometer alloy analyzers.

III. Basis for Determining Calibration Cycle

Determining the calibration cycle requires various professional knowledge and considerations of multiple factors. If a cycle is exceeded, it may lead to deterioration of quality characteristics, which can be attributed to mechanical wear, dust, performance, and frequency of testing. The sensitivity to changes in these factors depends on the type of portable spectrometer alloy analyzer. Higher-quality analyzers may be less affected, whereas lower-quality ones may be more affected. Therefore, each laboratory should determine the calibration cycle for each type of portable spectrometer alloy analyzer based on actual conditions.

The basis for determining the calibration cycle is:

(1) The frequency of use. Frequent use of portable spectral alloy analyzers can lead to a degradation in their measurement performance, which can be mitigated by shortening the calibration cycle. Of course, improving the raw material properties, manufacturing processes, and service life of the portable spectral alloy analyzers is also a crucial approach.

(2) Requirements for Measurement Accuracy. High-accuracy units may have their calibration cycles shortened appropriately. Each unit should decide based on its own actual circumstances what accuracy level is needed, and select the corresponding level. Aim for high accuracy when necessary and for low accuracy when appropriate, without blindly pursuing high accuracy to avoid unnecessary losses. However, too low of an accuracy level is also not advisable, as it may not meet usage requirements and result in losses for the work.

(3) Utilize the maintenance capabilities of the unit; if the unit's maintenance is excellent, shorten the calibration cycle accordingly; otherwise, extend it.

(4) Evaluate the performance of portable spectrometer alloy analyzers, with a focus on the levels of long-term stability and reliability. For portable spectrometer alloy analyzers of the same type with poor stability and reliability, the calibration cycle should be shorter.

(5) For measurement handheld spectrometers with alloy analyzers that are highly related to product quality and have special requirements, the calibration cycle is relatively shorter; otherwise, it is longer.

How to scientifically determine the calibration cycle?

Statistical Method:

Based on the similarity in structure, expected reliability, and stability of portable spectrometer alloy analyzers, the portable spectrometer alloy analyzers are initially grouped. Then, according to general conventional knowledge, the calibration cycles for each group of portable spectrometer alloy analyzers are preliminarily determined.

For each set of handheld spectrometer alloy analyzers, we tally the number of measurements that are off specification or otherwise non-compliant within the designated period. We then calculate the ratio of these handheld spectrometer alloy analyzers to the total number of compliant handheld spectrometer alloy analyzers within the given cycle. When identifying non-compliant handheld spectrometer alloy analyzers, we should exclude those that are obviously damaged or returned by users due to suspected or actual defects. If the proportion of non-compliant handheld spectrometer alloy analyzers is high, we should shorten the calibration cycle.

If it is proven that the proportion of non-compliant handheld spectrometer alloy analyzers is low, extending the calibration cycle may be economically reasonable. If it is found that a particular group of handheld spectrometer alloy analyzers (or those manufactured by a specific manufacturer or model) cannot operate as effectively as the others within the group, the group should be categorized as a separate group with a different cycle.

2. Hourly Rate Method

This method confirms the calibration cycle based on actual working hours. The portable spectrometer alloy analyzer can be connected to a timer indicator, and the analyzer is recalibrated when the indicator reaches the specified value. The main theoretical advantage of this method is that the number of portable spectrometer alloy analyzers to be verified and the verification cost are directly proportional to the time used. Additionally, it can automatically verify the usage time of the portable spectrometer alloy analyzers.

For instance, we use an oscilloscope from a certain company that allows us to directly check the duration of continuous use without connecting a timer, making it very convenient for management.

However, this method has the following drawbacks in practice:

When the portable spectrometer alloy analyzer is subject to drift or damage during storage, handling, or other circumstances, this method should not be used.

(2) Providing and installing appropriate timers incurs a higher initial cost and, due to potential interference from users, requires supervision, which adds to the expenses.

3. Comparative Method

When each portable handheld spectrometer alloy analyzer is calibrated according to the specified calibration cycle, and if the calibration results of consecutive cycles are all within the permitted range, the calibration cycle can be extended. However, if it is found to be out of the permitted range, the calibration cycle of the handheld spectrometer alloy analyzer should be shortened.

4. Chart Method:

In each calibration of the portable spectrometer alloy analyzer, a representative calibration point is selected, and their calibration results are plotted over time to form a curve. By analyzing these curves, the effective drift amount within one or several calibration cycles of the portable spectrometer alloy analyzer can be calculated. From the data of these charts, the optimal calibration cycle can be deduced.