Equipment Calibration Policy

The Mission Scientific Sensors listed on this page are calibrated on a fixed schedule. The calibration is coordinated by the Electronic Engineering Division (EED) of Marine Operations Pacific (MOP) and accomplished by the methods described below. Due to the intensive schedule kept by the ship during the normal field season operations, calibration of most sensors is performed during the ship's winter inport to allow adequeate turnaround time. The Electronic Engineering Division provides calibration data sheets (or CD ROMs, in the case of Seabird equipment) to the ship as well as maintaining them on file. The Ship's Chief Survey Technician (CST) also maintains shipboard files of sensor calibration records and data.

If a user desires a calibration more often than what is described below, the user will have to bear the expense for the extra calibration, as well as the shipping costs of the sensor to and from the ship. Such calibrations require advance planning and will be scheduled at a time when the sensor will not be needed by the ship so as not to impact on-going operations. As with standard calibrations, any extra calibrations will be coordinated by EED in consultation with the ship.

The calibration policy for individual sensors is provided below. Choose from the pull down list to go to a specific sensor or scroll down the page for information on all the sensors.

Autosalinometer (Autosal) (Guildline model 8400A)

Two units - one considered primary and one spare. Both units are calibrated annually.

*Note on Standard Seawater: The Miller Freeman maintains a limited stock of IAPSO standard seawater ampoules for periodic thermosalinograph (TSG) checks and autosal tests. Users requiring standard seawater ampoules in conjunction with routine salinity sample analyses on the autosal unit must provide their own stock of standard seawater for this purpose.

A paper published last year in the Journal of Atmospheric and Oceanic Technology (Vol. 15, 1072 -1075, August 1998) show that for the highest precision work, ampoules no more than 2 years old should be used. This assumes that they have been stored at room temperature. The data indicated that some batches of Standard Seawater may remain in calibration for much longer periods. Because it cannot be guaranteed which batches may have a very long life, it is recommended that ampoules no older than 2 years be used.
 

Barometer with digital output (Atmospherics Instruments)

Two complete units - one on-line unit and a spare in case of failure. The in-use unit is calibrated by the manufacturer once per year. The spare maintains its calibration and is re-calibrated the winter inport after use.
 

CTD (Seabird Model 911)

Two complete units - One is normally deployed as a single on-line unit while the second is reserved as a spare in case of failure of the on-line unit. Dual-sensor configuration for temperature and conductivity is available for one unit only. The standard sensors on the CTD are temperature, pressure, and conductivity. The system's manufacturer, Seabird Electronics (SBE), calibrates the on-line temperature and conductivity sensors on an annual basis, while the pressure sensor must be forwarded to SBE by the original vendor for calibration after every two years of use. The spare sensor package is re-calibrated after use, or, at a minimum of every 3 years, per Seabird's recommendation. The CTD deck unit has no periodic calibration requirement.
 

Thermosalinograph(Seabird Model 21)

Two units - one installed and one spare. The unit in use is calibrated on a yearly basis by the manufacturer, Seabird Electronics. If placed in service, the spare unit will be re-calibrated at the time of the next winter inport. Field checks of TSG data are performed on a periodic basis by the ship's CST following a procedure outlined by the Physical Oceanography Division (PhOD) of NOAA's Atlantic Oceanographic and Meteorological Laboratory (AOML).

The ship is equipped with spares for many of the sensors. Spare sensors are calibrated prior to being placed on board, and are considered to maintain proper calibration until used and/or for a time frame in accordance with vendor recommendations. Once a spare is placed in service, it will be re-calibrated ("post calibrated") during the next winter inport. Individual spare sensors calibrated in this manner are noted.