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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.
Overview
Slide 2
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
Temperature
Slide 3
Automatic Systems Laboratories Model F18 Primary Thermometry Bridge
Equipment
±0.1ppm (±25 µK) over entire range
Resolution of 0.003ppm (0.75 µK)
Linearity of <±0.01ppm
Stability of <0.02ppm/year
Slide 4
Standard Resistors:
Isotech Model 456
Equipment
25 ohm Standard resistor in Temperature controlled oil-Filled enclosure
Stability 1ppm/year
Slide 6
Standard Resistors:
Tinsley Model 5685A
Equipment
25 ohm Standard resistor in Temperature controlled Enclosure
Stability 2ppm/year
Slide 7
Jarrett-Isotech Water Triple point cells
Equipment
Calibrated to an uncertainty of +/- 0.000070°C (0.07mK)
Slide 8
Seabird SBE35 Standards thermometer
Equipment
Measurement Range -5 to +35 °C Initial Accuracy 0.001 °C Typical Stability (per year) 0.001 °C Resolution 0.000025 °C Sensor Calibration -1.5 to + 32.5 °C
Slide 10
Water Baths
Equipment
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
Slide 11
Water Baths
Equipment
Large Tank inside
dimension L48"xW26"xH30" (121.92 66.0 76.2cm)
Maximum volume 135 Gallons 613.5 Liters
Slide 12
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 0-12140 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.
Pressure
Slide 16
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.
Pressure
Slide 17
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.
Pressure
Slide 18
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.
Pressure
Slide 19
(GE Sensing) Ruska Model 2400 Hydraulic Dead Weight gauge 30-12140 PSI Accuracy 0.01% of reading
Equipment
Slide 20
Paroscientific 760-10K Portable pressure standard Accuracy: 0.008% of Full Scale Barometric Range Accuracy: ±0.08 hPa Resolution: 0.0001%
Equipment
Slide 21
Air Temperature:
Air Temperature sensors are calibrated similar to water temperature sensors.
Meteorology
Slide 22
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.
Meteorology
Slide 23
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
Equipment
Slide 24
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.
Meteorological
Slide 25
Paroscientific 765-16 Portable pressure standard Resolution: 0.0001% (<1 microbar) Accuracy: ±0.08 hPa or better.(1) Stability: 0.1 hPa /year or better(2)(3) Range: 500-1100 hPa (14.7-32.5 in Hg)
Equipment
Slide 26
(Esterline Weston) Ruska 7885 pressure standard Range 600-1150 hPa Accuracy <0.01% Full Scale
Equipment
Slide 27
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.
Software
Slide 28
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:
Clients
Slide 29
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 SBE911plus, SBE3plus, Meteorological Sensors
Scripps institution of Oceanography, Institute of Geophysics & Planetary Physics
Hydrophone
Scripps institution of Oceanography, Marine Physical Laboratory
SBE SEACAT