The WHOI CTD/Calibration Operations is provides CTD and hydrographic support for the seagoing scientists within and outside of WHOI.  A critical element in this support is the ability to calibrate and maintain the instrumentation in the inventory.  The annual WHOI NSF Instrumentation Proposal and other observational grants which have used the CTD and hydrography services have funded the purchase, operation and maintenance of a well-equipped facility, the CTD Calibration Lab, specifically oriented toward calibration of CTDs and related oceanographic sensors for WHOI and other educational, non-profit and governmental clients.  Occasional assistance is provided by the Lab to commercial entities on a cost-plus-fee, non-interference basis where no other facility has the resources.  The CTD Calibration Lab receives minimal ongoing support from WHOI departmental overhead funds, and is nearly entirely supported by charges to grants on an as-needed basis.

The CTD Calibration Lab maintains both primary physical standards and secondary transfer standards and support equipment, enabling high-accuracy calibration of temperature, conductivity and pressure sensors across the oceanographic range.  The availability of primary standards enables access for other WHOI groups, such as the Meteorological Calibration Lab, to NIST-defined temperature references in the course of their work.  Occasional standards intercomparison efforts are undertaken with other labs to maintain confidence in equipment and techniques.

The CTD Calibration Lab is located in the Clark Annex room 71 on the Quisset Campus, and is operated and maintained by Marshall Swartz of the Physical Oceanography Department.

Requests for calibration services must be made at least ten days in advance.  Please check the current CTD Calibration Lab Schedule here.

For all laboratory use requests, contact Marshall at 508-289-2246, or email to mswartz@whoi.edu.  In Marshall's absence, contact Jason Smith at 508-289-3618, or email to jsmith@whoi.edu.

Major capabilities of the CTD Calibration Lab are described under SETUPS and STANDARDS:

SETUPS:

Temperature calibration setups over the range of –2C to +30C and above:

• One 750-liter controlled temperature/salt bath (90cm dia. x 115cm depth) stable to +/- 0.002 C.
• Three 95-liter and one 50-liter Tronac temperature baths (custom sized) stable to +/- 0.000 2 C.

• Five 400-liter room temperature saltwater baths (70cm dia. X 105cm depth),
• Salt calibration in the 750-liter temperature/salt bath mentioned above.

STANDARDS:

Temperature reference points over the ITS-90 subrange 5 (-38.8344C to +29.7646C) include:

• Three gallium meltingpoint cells and maintenance ovens (YSI/Isotech and Pond Engineering),
• Five water triplepoint cells (Jarrett and Hart) and one four-cell triplepoint maintenance bath (Isotech),
• One mercury triplepoint cell and maintenance bath (YSI).

Temperature transfer standards between these reference points to the temperature bath setups include:

• ASL F18 AC resistance bridge with Tinsley 25.5 ohm NPL-calibrated standard resistor in Tinsley temperature-controlled air maintenance bath,
• Guildline 9975 DC resistance bridge with numerous Guildline standard resistors for DC ratio measurements from 1 ohm through 100K ohms,
• Hart 1575 DC resistance bridge with 2575 10-channel multiplexer,
• Five SPRTs (Rosemount 162-CE and L&N 8351) for use with above systems.

Pressure measurements are made by applying standard pressures from a Ruska 2480 deadweight table hydraulic system with calibrated masses, supplying hydraulic oil source pressures to units under test from 15 psig to 15,000 psig.  Accuracy and stability of the pressure output is monitored by a Paroscientific 760-10K laboratory pressure standard reference.

By Marshall Swartz, WHOI CTD/Calibration Operations, contact by phone 508-289-2246, mswartz@whoi.edu.

Updated April 16, 2007. File: ctdcal1.html