1. Shipboard Technical Support (STS) Calibration Facility
November 2010

2. Overview
The STS Calibration Facility provides precision temperature and pressure calibration services on oceanographic sensors such as, CTDs (conductivity temperature depth instruments) and other high precision oceanographic temperature and pressure sensors.
In addition, the facility also calibrates shipboard meteorological sensors such as air temperature, humidity and barometric pressure sensors.
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3. Temperature
The temperature calibration portion of the laboratory is outfitted with state-of-the-art equipment for fixed point and comparison temperature calibrations in the -5 to +35 °C range.
Data acquisition from the F18 bridge and temperature sensors at several temperature points.
Second standards thermometer as a redundant standard
Software processes the data, computes coefficients
Output - calibration report and XML file
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4. Equipment
Automatic Systems Laboratories Model F18 Primary Thermometry Bridge
±0.1ppm (±25 µK) over entire range
Resolution of 0.003ppm (0.75 µK)
Linearity of <±0.01ppm
Stability of <0.02ppm/year
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5. Equipment
SPRT Rosemount 162-CE Standard Platinum Resistance Thermometers
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6. Equipment Standard Resistors: Isotech Model 456
25 ohm Standard resistor in Temperature controlled oil- Filled enclosure
Stability 1ppm/year
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7. Equipment Standard Resistors: Tinsley Model 5685A
25 ohm Standard resistor in Temperature controlled Enclosure
Stability 2ppm/year
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8. Equipment Jarrett-Isotech Water Triple point cells
Calibrated to an uncertainty of +/ °C (0.07mK)
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9. Equipment Isotech Gallium Cell and apparatus 29.7646°C (±0.000025°C)
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10. Equipment Seabird SBE35 Standards thermometer
Measurement Range -5 to +35 °C
Initial Accuracy °C
Typical Stability (per year) °C
Resolution °C
Sensor Calibration -1.5 to °C
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11. Equipment Water Baths Hart Scientific Model 7112
11.2 Gallons 42 Liters 18"Depth
Range –10°C to 110°C (14°F to 230°F)
Stability ±0.0008°C
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12. Equipment Water Baths Large Tank
inside dimension L48"xW26"xH30 " ( cm)
Maximum volume 135 Gallons Liters
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13. Equipment Tronac temperature controller PTC-41 Range –5°C to 35°C
Stability ±0.0003°C
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14. Equipment
Lightnin Mixer
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15. Equipment Large Tank cooler
Neslab CFT Watt Recirculating Chiller
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16. Pressure
Primary pressure standards such as dead weight testers offer the highest level of pressure measurement precision and accuracy for most pressure calibration laboratories. At the STS Calibration Facility, we use a Ruska model 2400 hydraulic dead weight gauge to perform pressure calibrations in the pressure range of PSI. This system includes the piston hydraulic gauge, hand pump and mass set. The values of each weight in the mass set are obtained by correcting the reported mass for the effects of local gravity and buoyancy. Environmental sensors installed in the calibration lab monitors air temperature, relative humidity, barometric pressure and piston temperature data. During a pressure calibration the acquisition computer acquires, records and utilizes this environmental data to compute necessary corrections. The piston and weights are sent out to an accredited standards calibration lab for calibration every 4 years. The last calibration was done on October 7, 2009.
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17. Pressure
Factors that affect a pressure measurement process when conducted with a piston pressure gauge are:
Elastic distortions of the piston and cylinder.
Effects of gravity on the masses.
Temperature of the piston and cylinder.
Buoyant effect of the atmosphere upon the masses.
Hydraulic and gaseous pressure gradients within the apparatus.
Surface tension effects of the liquids.
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18. Pressure
Pressure calibrations are usually done at several temperatures in order to provide pressure coefficients that are corrected for the effect of temperature on the device being calibrated. The pressure sensor that is being calibrated will have it's pressure port connected to the Ruska dead weight gauge. Normally the device under test is subjected directly to the pressure of the dead weight gauge fluid. Air is bled from the pressure lines and the device is inserted into a water tank that is set at a stable temperature. A computer is setup to acquire data from the pressure sensor, F18 temperature bridge and environmental sensors. After the device has stabilized to the bath temperature then the pressure calibration can begin.
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19. Pressure
Pressure from the dead weight gauge is applied incrementally with each weight from zero pressure to the high end. With each added mass the dead weight gauge is brought to the floating position by the hand pump. After the pressure stabilizes at each pressure point the acquisition system records the necessary data. Once the high end is reached then the weights are removed in decremental order. Each mass is removed in sequence and data recorded at each level until the pressure returns back to zero. The bath is then changed to the next temperature and the process is repeated. In the case of a CTD the process is done at four different temperatures. After the data is acquired and saved to disk, the software processes the data, computes the new pressure coefficients for each device and produces processed data files and a calibration report.
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20. Equipment (GE Sensing) Ruska Model 2400 Hydraulic Dead Weight gauge
PSI
Accuracy 0.01% of reading
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21. Equipment Paroscientific 760-10K Portable pressure standard
Accuracy: 0.008% of Full Scale
Barometric Range Accuracy: ±0.08 hPa
Resolution: %
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22. Meteorology Air Temperature:
Air Temperature sensors are calibrated similar to water temperature sensors.
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23. Meteorology Humidity:
The Humilab Relative Humidity Generator is designed to perform U.S. National Institute of Standards and Technology (N.I.S.T.) traceable calibration of RH instruments and/or several smaller transmitters.
The humidity sensors that are being calibrated are inserted into the Humilab chamber. The Humilab is set to the desired humidity setting. After the sensors have stabilized data is acquired by a computer and recorded on disk. The Humilab is then set to the next point and the process is repeated until all points are completed. After the data is acquired and saved to disk, the software processes the data, computes the new coefficients for each device and produces processed data files and a calibration report.
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24. Equipment General Electric Measurement and Control Solutions Humilab
Relative Humidity range 10 to 90% RH at 77°F (25°C)
Accuracy:
±1.5% RH from 10% to 80% RH
±2% RH from 80 to 90% RH
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25. Meteorological Barometric Pressure:
The barometric pressure sensors that are being calibrated are inserted into the STS-built calibration chamber. The chamber is placed in a stable temperature bath and then pressurized by a pressure source to the desired pressure. After the sensors have stabilized data is acquired from the pressure standard by a computer and recorded on disk. The chamber is then pressurized at the next point and the process is repeated until all points are completed. The temperature bath is set to the next temperature point and the above process is repeated again. After the data is acquired and saved to disk, the software processes the data, computes the new coefficients for each device and produces processed data files and a calibration report.
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26. Equipment Paroscientific 765-16 Portable pressure standard
Resolution: % (<1 microbar)
Accuracy: ±0.08 hPa or better.(1)
Stability: 0.1 hPa /year or better(2)(3)
Range: hPa ( in Hg)
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27. Equipment (Esterline Weston) Ruska 7885 pressure standard
Range hPa Accuracy <0.01% Full Scale
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28. Software
The STS calibration software was developed at STS and is written entirely in labview. It incorporates the collective knowledge base, algorithms and procedures that the STS calibration facility has acquired and/or developed over many years. It consists of four main sections
Setup Calibration runs,
Acquire data,
Process data and Calculate coefficients, and
Generate Calibration reports.
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29. Clients
The Calibration Facility calibrates yearly the SIO/STS eight SeaBird SBE9 CTD's, quarterly the 24 SBE3plus temperature sensors and on an as needed basis the Meteorological sensors for the four Scripps Institution of Oceanography's ships. Along with these sensors, other laboratories have requested calibrations through the STS Calibration Facility. Some of these other laboratories include, but not limited to:
Institution
Instrument
Alfred Wegener Institute for Polar and Marine Research (AWI), Bremerhaven
Neil Brown Mark III CTD
USCGC HEALY
SBE911plus, SBE3plus, Meteorological Sensors
USCGC POLAR SEA
Scripps institution of Oceanography, Institute of Geophysics & Planetary Physics
Hydrophone
Scripps institution of Oceanography, Marine Physical Laboratory
SBE SEACAT
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30. Shipboard Technical Support (STS) Calibration Facility
November 2010