Enhancement of calibration and measurement capabilities of DHMZ calibration laboratory by interlaboratory comparison

One of the ways to promote education and knowledge, along with improvement of metrological infrastructure and monitoring the quality of results, as laboratories objectives, are inter-laboratory comparisons (ILCs) and proficiency testing (PT).The confidence in laboratory performance is essential not only for laboratories and their customers, but also for accreditation agencies and regulators. According to the requirements of ISO/IEC 17025, participation in interlaboratory comparisons is recognized as key element for assurance of calibration results quality.The Calibration laboratory (SOUL) of Meteorological and Hydrological Service of Croatia (MHSC) has the main role in the traceability assurance for all measurements under MHSC's responsibility. Dedicated to the continuous improvement of its performance as well as to the status within MHSC structure, but also, within national metrology structure, SOUL participated in a series of interlaboratory comparisons organized by the various institutions, but it also organized two ILC's independently, as pilot laboratory.This poster shows some of the experiences from those events, particulary how the implementation of the ILC and PT results has enhanced SOUL's calibration and measurement capabilities (CMC).

Introduction

Literature:

Methods

Krunoslav Premec; Marinko Marelja; Tatjana Radanović; Ivana ZastavnikovićMeteorological and Hydrological Service of Croatia, Gric 3, 10000 Zagreb, Croatia

Implemented improvements

Key words:

Conclusions

There are different criteria for evaluation of the results of participation in the interlaboratory comparisons. In ILCs in which SOUL has participated z'-score and En number were used as evaluation criteria. They are defined by the following equations:

ILCs have played an important role in achieving laboratory improvements in every aspect of its work; education, customer's confidence, better technical competence, procurement of sophisticated calibration equipment and in acquiring and enhancing of accreditation. Increased quality of laboratory's work has an important contribution to the customer's satisfaction, laboratory staff motivation and improvement of CMCs.Figures 5 and 6 shows chronological sequence of the achieved accreditation schemes and implemented calibration standards in SOUL.

Figure 6 Implementation of calibration standards in SOUL

Tel:00385 1 4565 607, Fax: 00385 1 4852 036

krunoslav.premec@cirus.dhz.hr

Results of ILCs

Figure 3 Results of CARDS-2006 ILC - relative humidity and temperature

Figure 2 Results of air quality parameters ILCs

Direct reading thermometers with TC and PRT as sensing elements

Liquid in glass thermometers

Platinum resistance thermometers

2002 2016

Pressure balanceRuska 2465A

SPRTIsotech 670

Humidity generatorHumor 20

Absolute radiometerPMO6

Pressure calibratorFluke Ruska 7250i

Mechanical thermometers

Pressure transducers with electrical output;Digital gauges

O3 analyzers CO analyzersGas cylinders

SO2 and NOxanalyzers

SO2 and NOx; CO, SO2 and NOx in synthetic air

Figure 5 Chronological overview of achieved accreditation schemes

2012 2016/17In process of

accreditation

In accordance with the requirements of ISO/IEC 17025 and the recommendations of the World Meteorological Organization (WMO), SOUL has been very actively involved in many ILC and PT events, either as a participant or as a pilot laboratory. The benefits of SOUL's participation in ILCs include confirmation of the quality and reliability of laboratory performance, identification of opportunities for improvements and enhancement of its work and improvements of CMCs. Some experienced poor or unsatisfactory results from ILCs led to an identification of the non-conformities and to undertaking the relevant corrective and preventive actions. Based on the SOUL experience, participation in ILCs represents a priceless opportunity for achievable improvements which lead to better quality assurance of calibration results and to higher confidence of the laboratory's customers.

Table 1 Calculated calibration factors for pyranometer comparison (Split, Croatia)

Where xi is the participant result, X is the assigned/reference value.

Where variables in the numerator are as for z'-score, while Uxi is the expanded uncertainty of a participant and Ux is expanded uncertainty of the reference laboratory.

Ozone generatorTEI 49C PS

Reference analyzersfor NOx, SO2 and CO

Reference analyzerfor SO2

Standard reference photometer SRP No.58

Temperature Temperature Temperature PressureRelative Humidity

Ozone CO H2S

SOUL has a long-term experience with ILC and PT events dating back to 2007. Since then SOUL participated in three events for temperature, one for pressure, two for relative humidity and four for solar radiation. These events were organized either by the World Meteorological Organization or by European Union through the projects CARDS and IPA. In the field of air quality, participation covered three ILCs organized by European Commission and World Health Organization. Results of ILC in air quality, shown on Figure 2, confirmed desired performance (those labeled with 1), while labels 2 and 3 initiated necessary improvements.

Good agreement with reference values for relative humidity and temperature shown on Figure 3, from CARDS 2006 ILC, was a major motivation for further extension of calibration range and improvement of CMCs. The same was true for pressure ILC, not shown here.

Accreditation, quality assurance, Interlaboratory comparisons (ILC), calibration and measurement capabilities (CMC), enhancement, MHSC-SOUL

2014 2015 2016

20102006 2014

Due to a lack of ILCs for certain parameters, and taking into account available infrastructure, SOUL took a lead and acted also as a pilot laboratory, following the requirements of ISO/IEC 17043. Facing a need for data quality assurance on national and regional level, SOUL has organized comparison of pyranometers and ILC for gas cylinders containing different amounts of NO, CO and SO2. Outcomes of the sub-regional pyranometer intercomparison for South-eastern Europe are shown in Table 1, while the enviroment where the event took place is shown at Figure 4.

Figure 4 Pyranometers on the mounting platform - comparison in Split-Marjan (Croatia)

Mostly used ILC evaluation scheme for air quality parameters (Figure 1) was adopted in 2008. It implements the z'-score method with the uncertainty requirements for calibration gases stated in the European standards.

www.meteo.hr

Figure 1 Evaluation scheme of ILC in the field of air quality

DI for O

zone