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 the Marine Operations Center (MOC) 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. The unit in use is returned to Guildline for checkout and repair as needed on a yearly basis. The spare is not returned for calibration until the winter after it's use. The annual maintenance by Guidline is not considered a "calibration"; however, they do perform a check against standard seawater*. This same procedure can be also be performed aboard the ship.

* Note on Standard Seawater:
The RONALD H. BROWN 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 in the Journal of Atmospheric and Oceanic Technology (Vol. 15, 1072 -1075, August 1998) has shown 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 BSE 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.
 

Fluorometer (Installed inline Turner)

Installed inline Turner Fluorometer with data output to the ship's data acquisition system (SCS). It is available for scientific use. Calibration is performed by ship's personnel on a yearly basis and involves an outlined procedure supplied with a calibration kit obtained from the equipment manufacturer (Turner).
 

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)

IMET Sensors - Several shipboard sensors comprising the "IMET" sensor set, were custom built by Woods Hole Oceanographic Instruments (WHOI) in Woods Hole, Massechussetts. These sensors are identical to the basic standard sensors deployed on UNOLS ships. Sensor calibration is performed by WHOI. Once calibrated, WHOI inserts the calibration data in the sensor's internal EPROM.

Precipitation rate

Units are difficult to calibrate and no standard method is available. The units have been compared to similar type units used by Pacific Marine Environmental Labs. Calibration is done if the units are suspected of not working properly.
 

Rain gauges:

Rain gauge (Hasse) (IMET sensor) - 1 unit. Measures vertical and wind driven rain. The unit separates wind driven rain in 4 sectors and measures wind speed by separate anemometer. The unit is calibrated on a yearly basis.
 

Rain gauge: Siphon (RM Young) - At the present time, there are 7 siphon rain gauge sensors deployed aboard the ship. The number of these non-WHOI Siphon Rain gauges installed will vary according to project requirements. Units are calibrated by the ship's ET or CST using onboard equipment. Calibration on installed gauges is performed once a year, with additional calibrations if a problem is suspected with a particular sensor or a project requirement.
 

Rain gauge: Siphon (RM Young) (IMET sensor) - Two Units. One installed and a spare. Units are calibrated by the ship's ET or CST using onboard equipment. This is done once a year or if a malfunction is suspected.
 

Rain gauge: Optical (Scientific Technology Inc.) - Two optical rain gauges on line. These units utilize optical sensing technology and are difficult to calibrate, with no standard method available. Inter-comparison with similar units or independent measurement means are conducted if additional project sensors are available and the shipboard sensors are suspected of not working
 

Short wave radiation sensor (WHOI sensor)

Two each - one installed and a spare. Calibration procedure is the same as the wind sensors.
 

Siphon Gauge (R.M. Young) (WHOI sensor)

Units are calibrated by the ship's ET or Survey Tech using onboard equipment. This is done once a year or if a malfunction is suspected.
 

Optical Rain Gauge (WHOI sensor)

The units have been compared to similar type units used by Pacific Marine Environmental Labs. Calibration is done if the units are suspected of not working properly.
 

Calibration of spare sensors

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.