Deep Ocean Temperature Measurement with an Uncertainty of 0.7 mK

The uncertainty of deep ocean temperature (~1°C) measurement was evaluated. The time drifts of six deep ocean standards thermometers were examined based on laboratory calibrations as performed by the manufacturer in triple point of water (TPW) cells and gallium-melting-point (GaMP) cells. The time drifts ranged from −0.11 to 0.14 mK yr−1. Three of the six thermometers were evaluated at the National Metrology Institute of Japan in five TPW cells and a GaMP cell, and the temperature readings agreed with the realized temperature of the national standard cells of Japan within ±0.14 and ±0.41 mK for TPW and GaMP, respectively. The pressure sensitivities of the deep ocean standards thermometers were estimated by comparison with conductivity–temperature–depth (CTD) thermometers in the deep ocean, and no notable difference was detected. Pressure sensitivities of the two CTD thermometers were examined by laboratory tests, and the results suggest that the deep ocean standards thermometers have no pressure sensitivity, at least up to 65 MPa. The position and attitude motion of the CTD system can affect temperature and salinity data quality. The overall expanded uncertainty of the deep ocean temperature measurement (up to 65 MPa) by the CTD thermometer calibrated in reference to the deep ocean standards thermometer is estimated to be 0.7 mK.

In Situ Calibration of the SeaBird 9plus CTD Thermometer

A Sea-Bird Electronics (SBE 35) deep ocean reference thermometer is used with the SBE 9plus CTD system to calibrate the SBE 3 ocean thermometers of the CTD. The SBE 35 is standardized in water-triple-point and gallium-melting-point cells. The SBE 3 is calibrated with the SBE 35 under the assumption that discrepancies between SBE 3 and SBE 35 data are due to pressure sensitivity, the viscous heating effect, and time drift of the SBE 3. Based on the results of an in situ calibration, the pressure sensitivity and the viscous heating effect were evaluated for 11 SBE 3 thermometers. Three SBE 3s showed little pressure sensitivity, and eight had pressure sensitivities of 1–2 mK at 6000 dbar. The average viscous heating effect on the standard SBE 3 measurements was 0.5 mK. Both the accuracy and precision of the in situ calibrated SBE 3 data at depths greater than 2000 dbar were 0.4 mK relative to the SBE 35 reference.

The Gallium Melting-Point Standard: A Determination of the Liquid—Solid Equilibrium Temperature of Pure Gallium on the International Practical Temperature Scale of 1968

The sharpness and reproducibility of the gallium melting point were studied, and the melting temperature of gallium in terms of IPTS-68 was determined. Small melting-point cells designed for use with thermistors are described. Nine gallium cells including three levels of purity were used in 68 separate determinations of the melting point. The melting point of 99.99999% pure gallium in terms of IPTS-68 is found to be 29.7714 ± 0.0014 °C; the melting range is less than 0.0005 °C and is reproducible to ±0.0004 °C.

The Gallium Melting-Point Standard: Its Role in Manufacture and Quality Control of Electronic Thermometers for the Clinical Laboratory

I discuss the traceability of calibration of electronic ther-mometers to thermometric constants of nature or to the National Bureau of Standards, from a manufacturer's basic standards through the manufacturing process to the user's laboratory. Useful electrical temperature sensors, their advantages, and means for resolving their disadvantages are described. I summarize our development of a cell for realizing the melting phase equilibrium of pure gallium (at 29.770 °C) as a thermometer calibration fixed point, and enumerate its advantages in the routine calibration veri-fication of electrical thermometers in the clinical chemistry laboratory.

The Gallium Melting-Point Standard: Its Role in Our Temperature Measurement System

The latest internationally-adopted temperature scale, the International Practical Temperature Scale of 1968 (amended edition of 1975), is discussed in some detail and a brief description is given of its evolution. The melting point of high-purity gallium (stated to be at least 99.99999 % pure) as a secondary temperature reference point is evaluated. I believe that this melting-point tem-perature of gallium should be adopted by the various medical professional societies and voluntary standards groups as the reaction temperature for enzyme reference methods in clinical enzymology. Gallium melting-point cells are available at the National Bureau of Standards as Standard Reference Material No. 1968.

The Gallium Melting-Point Standard: Its Application and Evaluation for Temperature Measurements in the Clinical Laboratory

I discuss the traceability of calibration of electronic ther-mometers to thermometric constants of nature or to the National Bureau of Standards, from a manufacturer's basic standards through the manufacturing process to the user's laboratory. Useful electrical temperature sensors, their advantages, and means for resolving their disadvantages are described. I summarize our development of a cell for realizing the melting phase equilibrium of pure gallium (at 29.770 °C) as a thermometer calibration fixed point, and enumerate its advantages in the routine calibration veri-fication of electrical thermometers in the clinical chemistry laboratory.