CONTENTS 
page 
7) INTRODUCTION 
3 DESCRIPTION OF EQUIPMENT 
10 TEMPERATURE CONTROL UNIT 
11 CALIBRATION OF REVERSING THERMOMETERS 
12 CONCLUSIONS 
13 RECOMMENDATIONS 
ILLUSTRATIONS 
page figure 
3 1 Controlled-temperature calibration facility 
4 2 Circulating system 
5 3 Thermal system 
6-7 4 Calibration tank, shown (A) before reversal of rack, (B) during reversal of rack, and 
(C) with rack removed 
8 5 Tank lid 
9 6 Tank window, reading telescope, and control panel 
11 7 Thermostat and resistance bridge 
INTRODUCTION Ten thermometers can be calibrated at a time against 
The NEL Controlled-Temperature Calibration Tank 
was designed to fill the Laboratory's need for a 
reliable and accurate temperature calibration facility 
for use primarily with deep-sea reversing thermom- 
eters. These thermometers are customarily read to 
0.01°C and, consequently, must be calibrated to at 
least that order of accuracy. A secondary use of the 
tank is the calibration of other temperature-measur- 
ing instruments such as thermistor beads and thermo- 
couples, which may require calibration accuracies 
approaching 0.001°C. 
Accurate calibration tanks have been produced 
in the past. The Dahl-Mosby tank’ which has been 
in operation at the Chr. Michelsen Institutt, Bergen, 
Norway, since 1945, consists essentially of an insu- 
lated cylinder which can be reversed end for end. 
10. Dahl and H. Mosby Calibration Tank for Reversing 
Thermometers (Christian Michelsen Institutt for Videnskap og 
Andsfrihet, Beretninger XI, 3) Griegs, 1945. 
the readings obtained on four standard thermometers. 
Woods Hole Oceanographic Institution produced a 
more elaborate twelve-thermometer tank in 1947 
which has heating and cooling elements controlled 
by Bourdon tube activated contacts.” A glass window 
and a movable telescope arrangement permit the 
thermometers to be read while submerged and com- 
pared against standard thermometers calibrated in 
0.01°C steps. Other tanks similar to the WHOI design 
are in use at the Pacific Oceanic Fisheries Investiga- 
tion, Honolulu, T. H.,2 and at the U.S. Bureau of 
Standards, Washington, D. C. 
2D. F. Bumpus and E.T. Penrose Equipment for Calibrating 
Deep Sea Reversing Thermometers (Woods Hole Oceanographic 
Institution, Ccmpletion Report No. 7) 1947. 
3H. Mann Plans and Specificaticns for a Constant Tempera- 
ture Tank for the Calibration of Deep Sea Reversing Thermom- 
eters (U.S. Fish and Wildlife Service, Pacific Ocean Fishing In- 
vestigations) (Unpublished manuscript) 23 May 1950. 
