Sea-Bird Electronics SBE 45 MicroTSG, User Manual

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APPLICATION NOTE NO. 42 Revised February 2010
ITS-90 TEMPERATURE SCALE
Beginning in January 1995, Sea-Bird's temperature metrology laboratory (based upon water triple-point and gallium melt cell,
SPRT, and ASL F18 Temperature Bridge) converted to ITS-90 (T90). These T90 standards are employed in calibrating
all
Sea-Bird temperature sensors, and as the reference temperature used in conductivity calibrations.
The international oceanographic research community continues to use IPTS-68 (T68) for computation of salinity and other
seawater properties. Therefore, following the recommendations of Saunders (1990) and as supported by the Joint Panel on
Oceanographic Tables and Standards (1991), our software and our instrument firmware (for instruments that can calculate and
output salinity and other seawater properties directly) converts between T68 and T90 according to the linear relationship:
T
68
= 1.00024 * T
90
The use of T68 for salinity and other seawater calculations is automatic in our software and in those instruments that directly
output salinity and other seawater parameters
.
Note: In our SEASOFT V2 suite of software programs, edit the CTD configuration (.con or .xmlcon) file to enter calibration
coefficients using the Configure Inputs menu in Seasave V7 (real-time data acquisition software) or the Configure menu in SBE
Data Processing (data processing software).
SBE 9 plus
(using SBE 3 plus temperature sensor)
, 16, 19, 21, and 25
(using SBE 3F temperature sensor)
Beginning in January 1995, Sea-Bird temperature calibration certificates began listing a set of coefficients labeled g , h , i , j , and
F0 , corresponding to ITS-90 (T90) temperatures. For user convenience and for historical comparison with older calibrations, the
certificates also continue to list a , b , c , d , and F0 coefficients corresponding to IPTS-68 (T68) temperatures. The T90 coefficients
result directly from T90 standards; the T68 coefficients are computed using the Saunders linear approximation.
SEASOFT supports entry of either the T90 or the T68 coefficients for these instruments. When selecting temperature as a
display/output variable, you must select which standard (T90 or T68) is to be used to compute temperature. SEASOFT
recognizes whether you have entered T90 or T68 coefficients in the configuration (.con or .xmlcon) file, and performs the
calculations accordingly, depending on which coefficients were used and which display variable type is selected.
•
If g, h, i, j, F0 coefficients (T90) are entered in the configuration file and you select temperature display/output variable type
as T68, SEASOFT computes T90 temperature directly and multiplies it by 1.00024 to display or output T68.
•
If a, b, c, d, and F0 coefficients (T68) are entered in the configuration file and you select temperature display/output variable
type as T90, SEASOFT computes T68 directly and divides by 1.00024 to display or output T90.
SBE 16 plus , 16 plus -IM, 16 plus V2, 16 plus -IM V2, 19 plus , 19 plus V2, 26 plus , 35, 35RT, 37 (all), 38,
39 and 39-IM, 45, 49, 51, 52-MP, 53, and all higher numbered instruments
For these instruments, all first manufactured after the switch of our metrology lab to ITS-90, Sea-Bird provides only one set of
temperature calibration coefficients, based on the T90 standards. These instruments all have user-programmable internal
calibration coefficients, and can output data in engineering units (°C, S/m, dbar, etc. as applicable to the instrument). When
outputting temperature in engineering units, these instruments always output T90 temperatures.
•
Instruments that can internally compute and then output salinity and other seawater parameters (for example,
SBE 37-SI) - Use of T68 for salinity and other seawater calculations is automatic; the instrument internally performs the
conversion between T90 and T68 according to the Saunders equation.
•
Instruments supported in SEASOFT (for example, SBE 19 plus V2) - Use of T68 for salinity and other seawater calculations
is automatic; the software performs the conversion between T90 and T68 according to the Saunders equation. When
selecting temperature as a display/output variable, you must select which standard (T90 or T68) is to be used to compute
temperature.
Sea-Bird Electronics, Inc.
13431 NE 20
th
Street
Bellevue, WA 98005
USA
Phone: (425) 643-9866
Fax: (425) 643-9954
E-mail: seabird@seabird.com
Web: www.seabird.com
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