Reversing Thermometer Set in Case
Date1940-2000
Object number00055901
DimensionsOverall: 380 × 405 × 133 mm
ClassificationsTools and equipment
Credit LineAustralian National Maritime Museum Collection Gift from Defence Science and Technology Group
DescriptionRectangular wooden case that contains 24 reversible thermometers.HistorySimilar to how water samplers function, this thermometer is designed to be able to take a recording at a designated depth when inverted and retain its’ reading until returned upright. These were usually attached to Nansen bottles and when messenger weights flipped the bottle ends closed, so too was the thermometer flipped and thus temperature recorded. It is able to remain unchanged until returned to the first position back on board. They are usually deployed in pairs where one is protected and the other not, both are inverted however the exposed is only used for the water temperature reading. The difference in temperature readings between the thermometers can be used to calculate water pressure.
Reversing thermometers come in two basic types; protected thermometers and unprotected thermometers, defined by whether the glass casing is present. These thermometers have an accuracy to 0.01°C, however when correcting for known fundamental problems, they become reliable to 0.02°C. Until the 1980s, reversing thermometers (also called mercury-in-glass thermometers) were the traditional method for measuring undersea temperatures. Digital thermometry has nearly replaced them with the development of thermistors being reliable to 0.001-0.005°C.SignificanceMercury thermometers were crucial to oceanographic data sets before contemporary apparatus were invented and widely used. Even with technological advancement over time, the reversing thermometers are still important as they provide a standard temperature measurement to test against electronic versions. All forms of new sensors use the mercury thermometers as a calibration standard to compare and evaluate performance. Some oceanographers still prefer this original method, believing it provides more reliable data even with the post-collection corrections needing to be made.
