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Instrument and equipment, periodic verification of standard substances and examples

　　1、Plan for periodic verification

The lab shall establish an annual verification schedule based on requirements, clearly specifying the equipment names, identification marks, equipment calibration/dating times, calibration/dating cycles, evaluation criteria, verification frequency, verification content, verification methods, and judgment criteria. The verification frequency can be determined based on factors such as the daily usage status of the instruments and equipment, and the results of the last calibration.

The primary objects for periodic verification in laboratory chemical testing equipment include:

　　a) Long service life, but with decreased stability and reliability in measurement accuracy, i.e., poor stability and significant drift in measuring equipment.

　　b) Highly frequent measurement equipment.

　　c) Measurement equipment frequently taken to the site for testing and used in harsh environments

　　d) Measurement of critical and key project data, and equipment with high accuracy requirements

　　2、Job instruction sheet for during-the-process inspections

Guideline for verification activities during the establishment of laboratory chemical testing instruments and equipment, at least including the following content:

a) Application Scope

b) Basis of Establishment

c) Environmental Requirements for Inspection

d) Verify the equipment used and measurement standards, standard substances, or verification standards

e) Verify Content

f) Verification Method

g) Criteria for Determination

h) Operation Steps

i) Results Evaluation and Conclusion

Instrumental Periodic Verification Methods and Result Assessment

3.1 Use of Measurement Standards

Equipment with accuracy requirements (accuracy grade or allowable error) can undergo periodic verification using metrological standards, with the requirement that the allowable error of the metrological standard be less than one-third of the allowable error of the verification equipment.

3.2 Use certified standard substances

When certified reference materials traceable to the International System of Units (SI) are available, periodic verification can be performed on the instruments and equipment used for their detection.

3.3 Utilize laboratory verification standards with known outcomes for interim verification and result assessment

Data for the verification standards are known, i.e., the verification standards are set by an expert laboratory that is independent of the measurement equipment to be verified, and the measurement uncertainty is less than that of the measuring equipment when the validity period is used for periodic verification of the instruments and equipment used for testing.

3.4 Conduct during-time verification and result judgment for the comparison of two equipment

When a laboratory has two identical measuring devices, if they can be traced back to the same metrological standard and the reliability of the calibration status of one device can be determined after calibration/verification, the method of comparing the two devices can be used. This involves utilizing the consistency of the measurement results from the comparative measurement device, while simultaneously conducting an intermediate check on the two measuring devices.

3.5 Conducting on-site verification and result assessment during the comparison of more than 3.5 devices

When the laboratory lacks a higher-grade measurement equipment for direct measurement methods, but has multiple devices with the same accuracy grade, the method of comparing multiple devices can be used. This involves utilizing the consistency of the measurement results from the comparative measurement equipment, while also conducting periodic verification of the multiple measurement devices.

3.6 Verify measurement performance in accordance with the specifications or procedures of calibration standards

If the laboratory meets the calibration (verification) conditions for testing equipment, a guidance document for periodic verification of instruments and equipment can be established based on the calibration specifications or verification procedures in the standard. This document should clearly define the environmental conditions, equipment, metrological standards, metrological requirements, as well as the methods for assessment and evaluation. Conduct periodic verification of the instruments and equipment according to the guidance document.