SBE 3 sensors are calibrated to ITS-90 temperature using Sea-Bird's computer-controlled calibration bath. Extremely well insulated, the baths provide a uniform toroidal circulation, yielding an overall transfer accuracy against an SPRT within 0.0002 °C. Repeatability at each of twelve individually mapped sensor positions is better than 0.0001 °C. Sea-Bird's metrology laboratory underpins the new temperature calibration baths. Following consultation with the U.S. National Institute of Standards and Technology, the metrology lab was configured to achieve temperature precision of 50 µK and accuracy of 0.0005 °C. To obtain this performance, premium primary references, including four Jarrett water triple-point cells (with maintenance bath) and an Isotech gallium melt cell, are operated in conjunction with two YSI 8163 standards-grade platinum resistance thermometers and an ASL F18 Automatic Temperature Bridge.
The calibration yields four coefficients (g, h, i, j) that are used in the following equation (Bennett, 1972):
T [°C] = [1 / (g + hln(fo/f) + iln²(fo/f) + jln³(fo/f) )] - 273.15
where T is temperature [°C], ln is the natural log function, and f is the SBE 3 output frequency [Hz]. Note that fo, an arbitrary scaling term used for purposes of computational efficiency, was historically chosen as the lowest sensor frequency generated during calibration. For all calibration results expressed in terms of ITS-90 temperatures, the fo term is set to 1000. Calibration fit residuals are typically less than 0.0001 °C.
SBE 3S Temperature Sensor Calibration Fit
SBE 3F Temperature Sensor Calibration Fit
SBE 3plus Temperature Sensor Calibration Fit
Bennett, A.S. (1972), "The calibration of thermistors over the range 0-30 C", Deep-Sea Research, Vol 19, 157-163
Steinhart, J.S. and S.R. Hart (1968), "Calibration Curves for Thermistors", Deep-Sea Research, Vol 15, 497
Specifications are subject to change without notice.
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