Secondary Calibration Research Articles

Reliable metrology for infrasound sensors

The reliable assessment of infrasound has become increasingly important in the last years. Reliable measurements require calibration of the employed sensors with traceability to the SI. While there is measurement equipment capable of measuring infrasound available, there is no sufficient calibration below 10 Hz. Traceability for airborne sound is currently realized by primary calibration methods which are applicable down to 2 Hz, with limitations below 10 Hz. Against that background, a primary and a secondary calibration setup have been developed at PTB. Together they enable the traceable calibration of a variety of infrasound sensors such as microphones, sound level meters or microbarometers. Moreover in practice, procedures are necessary which ensure reliable results in a field environment even with external disturbances. A field study was conducted comparing the performance of measurement microphones and microbarometers at a wind park. Emphasis was placed on different means of protection against wind induced noise. Additionally, a laboratory study investigated the influence of small damages to a microphone diaphragm on the reliability of the microphone. In this contribution, the newly developed calibration setups for infrasound sensors and the insights from the field and laboratory studies are presented.

Museomics reveal origins of East African Pleophylla forest chafers and Miocene forest connectivity

Here we present a nearly complete species-level phylogeny including 23 of the 25 known species of the forest-dwelling herbivorous scarab chafer beetle genus Pleophylla (Coleoptera: Scarabaeidae: Sericinae), based on the analysis of 950 nuclear genes (metazoan-level universal single-copy orthologs; mzl-USCOs). DNA sequences were obtained from freshly collected, ethanol-preserved samples and from dried museum specimens by target enrichment or genome shotgun sequencing. Alignment completeness of mzl-USCOs newly obtained here by target DNA enrichment of ethanol samples were very heterogenous and lower (29–62 %) than in Dietz et al. (2023a), while that of sequences recovered from dried samples was even lower (∼19 %). Alignment completeness of the sequences obtained from low coverage shotgun sequencing was highest (∼92 %), although the average coverage was much lower than for the target enrichment samples. We used the resulting phylogeny to reconstruct the historical biogeography of the group. To estimate a time-calibrated tree, we combined the mzl-USCO data of Pleophylla with a nucleotide alignment from an available transcriptomic dataset of Scarabaeoidea and used two different sets of secondary calibration points. Despite the problems associated with the capture rate of mzl-USCO sequences from museum specimens, we were able to infer a well-resolved phylogeny of the genus Pleophylla that also provided reliable estimates of the phylogenetic position of species for which we had little sequence data. Our study clearly identified South Africa as the geographic origin of Pleophylla. Timing and biogeographic history confirm a persistent fragmentation of forests since the Eocene. The occurrence of only one long-distance dispersal event from southern Africa to the Eastern African Arc even during the Miocene highlights the limited dispersal possibilities for these forest-adapted chafers, which do not seem to have had important northerly range expansions along hypothetical forest corridors during the Pleistocene.

Studies on a Mobile Acoustic Emission Sensor Verification Device

Despite the fact that there are two ASTM standards, ASTM 1106 for primary calibration and ASTM E 1781 for secondary calibration of acoustic emission sensors, there is no company or institution currently offering calibration services based on these standards due to lack of availability or practical aspects. Another option is CEN ISO/TR 13115, which needs a large volumetric propagation medium leading to similar practical limitations as for the ASTM standards. Many acoustic emission users try to fill the gap of calibration services by using simplified verification standards. However, there is currently no verification standard suitable for using in the field. In that sense, one ambition of the project CalibrAEte is to establish a new standard for primary and secondary calibration that can be implemented in laboratories without a huge invest. Another objective of the project is to establish a verification procedure using a device to verify acoustic emission sensors by a wave-based approach in the field. The proposed approach uses a durable propagation medium that carries the elastic waves from a repeatable source to the sensor under test. This research focuses on such a mobile verification device in the sense that an optimal configuration is proposed. This contribution will present the major aspects and details of an acoustic emission sensor verification setup that can be used not just in the laboratory environment but also in harsh field conditions. It will be shown the performance of the reference sensor developed for this purpose along with the setup itself, which was partially developed by aid of numerical methods. Also, experimental results in different temperature conditions, will be presented to assess the robustness of the setup. It also be presented a sensitivity analysis of the setup using different sensors in different stages of degradation.

Historical biogeography of North American killifishes (Cyprinodontiformes) recapitulates geographical history in the Gulf of México watershed

Abstract We analysed phylogenetic relationships within a major clade of Cyprinodontiformes (Teleostei) that includes five families of North American killifishes. We used DNA sequences from five genes for 130 species, with four fossil calibrations and three secondary calibrations, to generate a time-calibrated phylogeny. We estimated diversification rates, ancestral areas, and ancestral habitats for each node. Findings were interpreted within a detailed biogeographical synthesis. The results indicate that the clade arose in the Eocene along the Gulf of México coast. The speciation rate was uniform through time, except for acceleration in Cyprinodontidae after ~10.9 Mya. In other families, neither viviparity nor marine-to-freshwater transition was associated with accelerated speciation. Sea-level fluctuations might have created a speciation pump by stimulating cycles of dispersal and vicariance along the coast. Diversification also included many cases of inland immigration from coastal ancestors. For upland lineages, ancient river drainages accord with lineage distributions, including enigmatic disjunctions in Goodeidae and Fundulus. Diversification in uplands occurred via barrier displacement within alluvial or tectonically active landscapes. Killifishes also display high environmental tolerance and persist within harsh, peripheral environments unsuitable for most other fishes. Hence, a combination of clade antiquity, adaptability, dynamic geography, and persistence can explain the living diversity of New World killifishes.

Electric Calibration for Heterodyne Laser-Doppler Vibrometers at High Frequency

Abstract Calibration for Heterodyne Laser-Doppler Vibrometers (HLDV) is important for its accuracy and reliability. ISO 166063-41 provides primary and secondary calibration specifications for HLDV only in the frequency range from 0.4Hz to 50kHz, which can’t meet current demand for higher frequency. To be specific, the vibration exciter limits calibration frequency to a higher range. With this in mind, the electric calibration is presented. As a substitution method, the high precision arbitrary waveform generator replaces the optical module to output synthesized Doppler heterodyne signals which can cover all the required frequency. In addition, a commercial demodulator is used for calibration in the frequency range up to 1MHz. By theoretical introduction and experimental verification, this method offers significant improvement and thus potential over existing methods for HLDV calibration.

The New Horizons Extended Mission Target: Arrokoth Search and Discovery

Following the Pluto flyby of the New Horizons spacecraft, the mission provided a unique opportunity to explore the Kuiper Belt in situ. The possibility existed to fly by a Kuiper Belt object (KBO), as well as to observe additional objects at distances closer than are feasible from Earth-orbit facilities. However, at the time of launch no KBOs were known about that were accessible by the spacecraft. In this paper we present the results of 10 yr of observations and three uniquely dedicated efforts—two ground-based using the Subaru Suprime Camera, the Magellan MegaCam and IMACS Cameras, and one with the Hubble Space Telescope—to find such KBOs for study. In this paper we overview the search criteria and strategies employed in our work and detail the analysis efforts to locate and track faint objects in the Galactic plane. We also present a summary of all of the KBOs that were discovered as part of our efforts and how spacecraft targetability was assessed, including a detailed description of our astrometric analysis, which included development of an extensive secondary calibration network. Overall, these efforts resulted in the discovery of 85 KBOs, including 11 that became objects for distant observation by New Horizons and (486958) Arrokoth, which became the first post-Pluto flyby destination.

Overview and current challenges at the Calibration Laboratory of the Paul Scherrer Institute

The Calibration Laboratory of the Paul Scherrer Institute (PSI) is a secondary calibration laboratory accredited by the Swiss Accreditation Service (SAS) in accordance with ISO 17025. It also acts as a verification body authorized by the Swiss Federal Institute of Metrology (METAS). The Laboratory is equipped with X-ray, gamma and neutron irradiation facilities, providing characterized reference radiation fields for gamma 137Cs, 60Co, narrow spectrum X-rays from N-15 to N-300 and neutron radionuclide sources 252Cf, 252Cf (D2O-moderated) and 241Am-Be. The laboratory performs routine calibrations, organizes intercomparison measurements for individual monitoring services in Switzerland, and participates in various research projects, e.g., by performing irradiations in reference fields. For this reason, the proper characterization of reference radiation fields is of utmost importance for ensuring high quality irradiations and calibrations of personal dosemeters and radiation protection instruments. In this contribution, we provide an overview of the irradiation facilities at the Calibration Laboratory at PSI and discuss the challenges of characterizing reference radiation fields. In particular, we will discuss the factors affecting the determination of the distance between the source and irradiated dosemeters and detectors, as well as issues related to 252Cf decay and contribution of 250Cf. We will also demonstrate the use of Monte-Carlo simulations in determining the optimal position of the source and irradiation facility within the irradiation room.

Phylogenetic relationships and historical biogeography of silkmoths (Lepidoptera: Bombycidae) suggest an origin in Southern Gondwana

Silkmoths (Bombycidae) have a disjunct distribution predominantly in the Southern Hemisphere and Asia. Here we reconstruct the phylogenetic history of the family to test competing hypotheses on their origin and assess how vicariance and long-distance dispersal shaped their current distribution. We sequenced up to 5,074 base pairs from six loci (COI, EF1-α, wgl, CAD, GAPDH, and RpS5) to infer the historical biogeography of Bombycidae. The multilocus dataset covering 20 genera (80 %) of the family, including 17 genera (94 %) of Bombycinae and 3 genera (43 %) of Epiinae, was used to estimate phylogenetic patterns, divergence times and biogeographic reconstruction. Dating estimates extrapolated from secondary calibration sources indicate the Bombycidae stem-group originated approximately 64 Mya. The subfamilies Epiinae (South America) and Bombycinae (Australia, Asia, East Palaearctic, and Africa) were reciprocally monophyletic, diverging at c. 56 Mya (95 % credibility interval: 66–46 Mya). The ‘basal’ lineage of Bombycinae — Gastridiota + Elachyophtalma — split from the rest of Bombycinae c. 53 Mya (95 % credibility interval: 63–43 Mya). Gastridiota is a monobasic genus with a relictual distribution in subtropical forests of eastern Australia. The Oriental and African genera comprised a monophyletic group: the Oriental region was inferred to have been colonized from a long-distance dispersal event from Australia to South-East Asia c. 53 Mya or possibly later (c. 36–26 Mya); Africa was subsequently colonized by dispersal from Asia c. 16 Mya (95 % credibility interval: 21–12 Mya). Based on the strongly supported phylogenetic relationships and estimates of divergence times, we conclude that Bombycidae had its origin in the fragment of Southern Gondwana consisting of Australia, Antarctica and South America during the Paleocene. The disjunction between South America (Epiinae) and Australia (Bombycinae) is best explained by vicariance in the Eocene, whereas the disjunct distribution in Asia and Africa is best explained by more recent dispersal events.

Study of a Red Clump Giant, KIC 11087027, with High Rotation and Strong Infrared Excess—Evidence of Tidal Interaction for High Lithium Abundance

This Letter presents results from Kepler photometric light curves and a high-resolution spectroscopic study of a super-Li-rich giant KIC11087027. Using the light-curve analysis, we measured the star’s rotational period P rot = 30.4 ± 0.1 days, which translates to rotational velocity V rot = 19.5 ± 1.7 km s−1. The star’s location in the Hertzsprung–Russell diagram, derived values of 12C/13C = 7 ± 1 and [C/N] = −0.95 ± 0.2, and the inferred asteroseismic parameters from secondary calibration based on spectra suggest the star is a low-mass red clump giant in the He-core burning phase. Using Gaia data, we found evidence of variation in radial velocity and proper motion, indicative of presence of an unresolved binary. The large V rot is probably a result of tidal synchronization combined with the aftereffects of He flash, in which the size of the star is reduced significantly. The simultaneous presence of features like high rotation, very high Li abundance, strong dust shell, and strong flares in a single star is relatively uncommon, suggesting that the star experiencing tidal synchronization has recently undergone He flash. The results pose a question whether the binary interaction, hence the high rotation, is a prerequisite for the dredging up of the high amounts of Li from the interior to the photosphere during or immediately after the He-flash event.

Two-stage correction prediction of wind power based on numerical weather prediction wind speed superposition correction and improved clustering

The unavoidable wind power prediction error poses a challenge for wind power to participate in day-ahead scheduling plan. This paper proposes a two-stage correction method considering NWP wind speed and power correction. Firstly, this paper fully considers the historical similarity of NWP wind speed, and adopts the improved clustering distance for segment matching and wind speed correction based on the extracted most relevant trend component, which enhances the utilization of NWP information and avoids the randomness and uncertainty of the intelligent correction method, and gram angular field (GAF) and stacked autoencoder (SAE) are used for feature extraction and conditional variational autoencoder (CVA) is used to generate specific samples to ensure the adequacy of the clustering process. Secondly, considering the historical similarity of error of predicted power, the power is further corrected based on the proposed weighted double-constraint to realize the secondary calibration. The Proposed method is applied to several wind farms in China to verify its effectiveness. The results show that the proposed method reduces the NRMSE by 3.82 % and NMAE by 3.40 % compared with direct prediction in the wind farms in western Inner Mongolia, which is important for promoting wind power consumption and maintaining the safe and stable operation of the power system.

Analysis of the Design and Application of a Novel CT Secondary Cable Line Calibrator

With the rapid development of electrical power systems, ensuring the accuracy and reliability of power transmission has become particularly crucial. The secondary cable line calibrator for current transformers (CT) plays an essential role in calibrating electrical power systems. It is not only related to the safe operation of the system but also directly impacts the accuracy of energy metering. This study aims to design and analyze an efficient CT secondary cable line calibrator to explore its application effects in the power system. By thoroughly analyzing the characteristics of CT secondary cable lines and the design requirements of the calibrator, this paper proposes an innovative design scheme for the calibrator. This device demonstrates significant effects in enhancing the accuracy and stability of power system calibration, providing robust technical support for the optimization and upgrade of the power system. This research not only offers a theoretical basis and practical guidance for the design and application of CT secondary cable line calibrators but also contributes new ideas and methods for the precise calibration and efficient management of the power system.

Phylogenetics, character evolution, and historical biogeography of the Neotropical genus Besleria (Gesneriaceae)

Abstract Besleria, a genus of perennial herbs, shrubs, or small trees growing in the understorey of rainforests, is one of the largest genera of neotropical Gesneriaceae, with over 165 species. Despite the ecological importance and ubiquity of Besleria in rainforest ecosystems, taxonomic and evolutionary studies of Besleria are limited. Here, we generated a phylogenetic analysis of Besleria using four nuclear and chloroplast DNA regions (ITS, matK, rps16, and trnL-trnF) covering more than 50% of the recognized species, along with two secondary calibration points to infer divergence times. Our results support the monophyly of Besleria and allowed us to revise the infrageneric classification and biogeographical history of the genus. We identified five major clades that do not correspond to sections or subsections in previous classifications. These clades are well circumscribed geographically but remain difficult to characterize using previously hypothesized morphological characters. Biogeographical reconstructions indicate an origin in the northern Andes during the Middle Miocene (ca. 15 Mya). The current distribution patterns of this plant group have been significantly shaped by geological and climatic events, particularly Andean uplift and the formation of the Panama Isthmus.

DateLife: Leveraging Databases and Analytical Tools to Reveal the Dated Tree of Life.

Chronograms-phylogenies with branch lengths proportional to time-represent key data on timing of evolutionary events, allowing us to study natural processes in many areas of biological research. Chronograms also provide valuable information that can be used for education, science communication, and conservation policy decisions. Yet, achieving a high-quality reconstruction of a chronogram is a difficult and resource-consuming task. Here we present DateLife, a phylogenetic software implemented as an R package and an R Shiny web application available at www.datelife.org, that provides services for efficient and easy discovery, summary, reuse, and reanalysis of node age data mined from a curated database of expert, peer-reviewed, and openly available chronograms. The main DateLife workflow starts with one or more scientific taxon names provided by a user. Names are processed and standardized to a unified taxonomy, allowing DateLife to run a name match across its local chronogram database that is curated from Open Tree of Life's phylogenetic repository, and extract all chronograms that contain at least two queried taxon names, along with their metadata. Finally, node ages from matching chronograms are mapped using the congruification algorithm to corresponding nodes on a tree topology, either extracted from Open Tree of Life's synthetic phylogeny or one provided by the user. Congruified node ages are used as secondary calibrations to date the chosen topology, with or without initial branch lengths, using different phylogenetic dating methods such as BLADJ, treePL, PATHd8, and MrBayes. We performed a cross-validation test to compare node ages resulting from a DateLife analysis (i.e, phylogenetic dating using secondary calibrations) to those from the original chronograms (i.e, obtained with primary calibrations), and found that DateLife's node age estimates are consistent with the age estimates from the original chronograms, with the largest variation in ages occurring around topologically deeper nodes. Because the results from any software for scientific analysis can only be as good as the data used as input, we highlight the importance of considering the results of a DateLife analysis in the context of the input chronograms. DateLife can help to increase awareness of the existing disparities among alternative hypotheses of dates for the same diversification events, and to support exploration of the effect of alternative chronogram hypotheses on downstream analyses, providing a framework for a more informed interpretation of evolutionary results.

Assembling an illustrated family‐level tree of life for exploration in mobile devices

AbstractSince the concept of the tree of life was introduced about 150 years ago, a considerable fraction of the scientific community has focused its efforts on its reconstruction, with remarkable progress during the last two decades with the advent of DNA sequences. However, the assemblage of a comprehensive and explorable tree of life has been a difficult task to achieve due to two main obstacles: (i) information is scattered into several individual sources and (ii) practical visualization tools for exploring large trees are needed. To overcome both challenges, we aimed to synthesize a family‐level tree of life by compiling over 1400 published phylogenetic studies, choosing the source trees that represent the best phylogenetic hypotheses to date based on a set of objective criteria. Moreover, we dated the tree by employing over 550 secondary calibrations using publicly available sequences for more than 5000 taxa and by incorporating age ranges from the fossil record for over 2800 taxa. Additionally, we developed a mobile app for smartphones to facilitate the visualization and exploration of the resulting tree. Interactive features include exploration by the zooming and panning gestures of touch screens, collapsing branches, visualizing specific clades as subtrees, a search engine, and a timescale to determine extinction and divergence dates, among others. Small illustrations of organisms are displayed at the terminals to better visualize the morphological diversity of life. Our assembled tree currently includes over 7000 families, and its content will be expanded through regular updates to cover all life on earth at the family level.

Portable XRF applied to regional bedrock mapping in Quebec, Canada

Whole-rock geochemistry yields better geological maps of the bedrock, since it allows, for example, visually similar lithologies to be distinguished. However, conventional laboratory geochemistry is not available in the field during a mapping campaign. Portable X-ray fluorescence (pXRF) analyzers can produce fit-for-purpose data rapidly, and constitute a useful complement to conventional geochemistry in a bedrock mapping project. The pXRF data can be employed (i) while still in the field, to orient the mapping campaign; (ii) to prepare a preliminary geological map back in the office; and (iii) to interpolate between conventional whole-rock analyses on the final map. The latter application requires a matrix-matched secondary calibration of the pXRF data to improve its accuracy. Attention must also be given to precision issues, as well as potential instrument drift and analytical interferences.This paper summarizes recent efforts to systematically integrate quantitative pXRF data in government mapping projects within the Province of Quebec (Canada). We first demonstrate how an Olympus Vanta series M pXRF analyzer was commissioned and calibrated. We then show how the pXRF data was systematically acquired and utilized during a 1:50,000 to 1:20,000 mapping campaign in a Precambrian greenstone belt setting (Abitibi Subprovince). Before the mapping began in 2021, volcanic rocks in the study area were supposed to consist of only two mafic tholeiitic formations, called Obatogamau and Bruneau. Integrating pXRF into this project meant that while still in the field and immediately afterwards during preparation of the preliminary map: (1) a marker horizon representing the top of the Obatogamau Formation was chemically identified and then traced laterally; (2) the felsic Waconichi Formation was recognized despite the high metamorphic grade and also traced laterally just above the marker horizon; (3) the Bruneau Formation was shown to be much more continuous than previously known and to have Mg-tholeiites at its base, like in the type locality; (4) the Blondeau Formation was shown to occur above the Bruneau Formation. Within the volumetrically dominant Obatogamau Formation, Fe-tholeiites were also distinguished from visually similar Mg-tholeiites, which allowed these subunits to be traced while still in the field, leading to a more detailed map. Later, after the conventional laboratory chemistry had been received, the final geological map was prepared, but it was very similar to the preliminary map, confirming the satisfactory performance of the pXRF method for this application. However, we do note some issues and limitations even with the latest generation of analyzers.

Research on measurement error calibration method of TDLAS oxygen concentration detection based on CFD and SVR

Tunable Diode Laser Absorption Spectroscopy (TDLAS) enables rapid online detection of gas concentrations through the absorption of spectral lines by gas molecules in the infrared spectral region. In order to solve the problem of hysteresis and large errors of the measured values relative to the true values when TDLAS detects gases with simultaneous changes in oxygen concentration and flow rate in real-time, the CFD simulation model of the absorption cell is established by Fluent. The relationship between the measured value of TDLAS and the actual concentration change under different flow conditions is analyzed by simulation data, and the support vector machine regression calibration model is established to reduce the measurement error. It successfully reduces the average error from 5.844% to 2.899%, which is a reduction of 50.7%. The average error is further reduced to 1.308% after a secondary calibration based on different starting concentrations. The method is suitable for concentration detection in the presence of rapid changes in oxygen concentration.

Inter-laboratory comparison of a digital multimeter measurement in Turkey

The standard ISO/IEC 17043:2023 specifies the general requirements for proficiency testing providers and covers the development, operation, and reporting of proficiency testing schemes. The standard aims to ensure that the measurement results obtained by different laboratories are comparable and traceable to international measurement standards. Inter-laboratory comparisons are still rare in the meteorological services network of calibration laboratories, and there are not enough bodies accredited with the ISO/IEC 17043:2023 standard in Turkey. The existing inter-laboratory comparison measurements do not fully comply with the requirements of ISO/IEC 17043:2023 and are not compatible with the measurement capabilities and scopes of the laboratories, leading to difficulties when comparing meteorological data from different laboratories. This article presents a case study of a digital multimeter interlaboratory comparison measurement in accordance with the ISO/IEC 17043:2023 standard. The results obtained were analysed using statistical methods (En score) and compared to the reference values provided by a secondary accredited calibration laboratory. The analysis showed that the measurement results obtained by the participants were consistent and generally within the acceptable range of En. The case study presented in this paper demonstrates the effectiveness of the standard in ensuring reliable measurement results in a practical setting.

GUI development for SSDL to calibrate photon measuring equipment

Current legislation mandates the inspection and calibration of operational survey radiation monitoring instruments used in nuclear medicine, radiotherapy departments, and other fields utilizing ionizing radiation sources. To comply with national and international radiation protection standards, Morocco's National Secondary Standard Dosimetry Laboratory provides reliable calibration results with high accuracy and covers various measurement ranges using attenuators provided by the automated Gamma G10 irradiator or validated beam qualities produced by the X-ray irradiator type X80–320 kV.This study aims to develop a digital graphical user interface using Python programming language, designed for calibrating radiation protection measuring instruments . The interface is intended to facilitate all operations and calculations related to determining calibration factors and measurement uncertainties in accordance with the ISO 4037 standard, ensuring minimal processing time and minimizing potential error sources . The interface enables calculations to be recorded, as well as the establishment and electronic archiving of the calibration certificate and the report in PDF format using the Hypertext Preprocessor FPDF library (PHP FPDF). With the development of this interface, multiple instruments can be processed per day with high accuracy, streamlining the calibration process and improving efficiency.•The importance of compliance with international standards to ensure the quality and reliability of measurements in radiation protection was examined.•Description of X-ray and Gamma-ray irradiators designed for the calibration of radiation protection measuring instruments within the Secondary Dosimetry Calibration Laboratory (SSDL) which is a member of the WHO/IAEA network within the National Center for Radiation Protection of Morocco•Graphical User Interface using python for the calibration of photon measurement instruments for radiation protection purposes was developped.

Multivariate control charts for calibration of hydrophones using the Mahalanobis statistic

Statistical analysis of data to ensure the validity of calibrations can be challenged when the measurement model describes a process and result that spans a high-dimensional parameter space. Calibration of hydrophones presents one such case whereby the sensitivity to acoustic pressure is calculated using measured values for several different quantities and the result is needed at many excitation frequencies distributed over a large bandwidth. We addressed this challenge by developing a multivariate statistical analysis procedure that supports efficient and effective process control for hydrophone calibrations. We first characterize the in-control condition by the mean and covariance of measurements expressed in a p-dimensional parameter space using a curated training data set. We then test subsequent measurements against a control limit using Hotelling’s T 2-test to compare the current measurement process to the training data. We report a case study for secondary calibration of hydrophones spanning a frequency range of 1 kHz–200 kHz where we detected an emergent defect in the laboratory’s calibrated reference hydrophone by inspection of data presented in multivariate control charts. Process control data collected during calibration services exceeded the control limits in intermediate and high-frequency bands by factors of 5.1 and 11.2, respectively. The process remained in control for the low-frequency band. These observations were consistent with misalignment of the reference hydrophone’s sensitive element, which we confirmed upon disassembly, inspection and repair of the instrument.

Recommendations for Setting a Criterion for Assessing Commutability of Secondary Calibrator Certified Reference Materials.

A secondary higher-order calibrator is required to be commutable with clinical samples to be suitable for use in the calibration hierarchy of an end-user clinical laboratory in vitro diagnostic medical device (IVD-MD). Commutability is a property of a reference material that means results for a reference material and for clinical samples have the same numeric relationship, within specified limits, across the measurement procedures for which the reference material is intended to be used. Procedures for assessing commutability have been described in the literature. This report provides recommendations for establishing a quantitative criterion to assess the commutability of a certified reference material (CRM). The criterion is the maximum allowable noncommutability bias (MANCB) that allows a CRM to be used as a calibrator in a calibration hierarchy for an IVD-MD without exceeding the maximum allowable combined standard uncertainty for a clinical sample result (umaxCS). Consequently, the MANCB is derived as a fraction of the umaxCS for the measurand. The suitability of an MANCB for practical use in a commutability assessment is determined by estimating the number of measurements of clinical samples and CRMs required based on the precision performance and nonselectivity for the measurand of the measurement procedures in the assessment. Guidance is also provided for evaluating indeterminate commutability conclusions and how to report results of a commutability assessment.