Images(4)

Thermometer Container

Date1980s

Object number00055784

NameContainer

MediumWood, metal

DimensionsOverall: 526 g

ClassificationsTools and equipment

Credit LineAustralian National Maritime Museum Collection Gift of CSIRO

Terms

DescriptionWooden rectangular box used to store a thermometer (00055785).HistoryThe reversing thermometer was invented in 1874 by Negretti and Zambra, London. Until the 1980s these thermometers, also called mercury-in-glass thermometers, were the traditional method for measuring undersea temperatures. Digital thermometry has nearly replaced this method with the development of thermistors. However, mercury thermometers were crucial to oceanographic data sets before more accurate CTDs were invented and widely used. 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. With today’s advancements these have been improved to between 0.001 and 0.005°C with high-quality thermistors. Similar 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 is temperature readings between the thermometers can be used to calculate water pressure.SignificanceEven with technological advancement over time, the mercury-in-glass thermometers are still important as they provide a standard temperature measurement to test against electronic versions. All forms of new sensors use the reversing 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.