reversing thermometer
Noun: A reversing thermometer is a specialized scientific instrument designed to measure and record the temperature at a specific depth in a body of water. Its key feature is a mechanism that "reverses" or breaks the mercury column upon retrieval, thereby preserving the temperature reading from the depth at which it was triggered.
The reversing thermometer is used almost exclusively in oceanography and limnology (the study of inland waters). It is typically deployed attached to a water-sampling bottle or a profiling array. The thermometer is lowered to the desired depth, where a messenger weight triggers its reversal mechanism, capturing the temperature. The reading is then taken after the instrument is brought back to the surface.
- Oceanographers rely on reversing thermometers to obtain precise sub-surface temperature profiles.
- The data from the reversing thermometer confirmed the presence of a cold water layer at 500 meters.
- Before the advent of digital CTD (Conductivity, Temperature, Depth) profilers, reversing thermometers were the standard tool for deep-water temperature measurements.
- Paired Deployment: In high-accuracy work, reversing thermometers are often used in pairs—one protected (to record the temperature) and one unprotected (to record the temperature affected by pressure at depth). Comparing the two readings allows for corrections and calculations.
- Historical Context: While largely superseded by electronic sensors for routine work, the reversing thermometer is still considered a valuable standard for calibrating modern electronic instruments due to its high accuracy and mechanical simplicity.
- Protected Reversing Thermometer: A type of reversing thermometer encased in a protective glass shell to shield it from the effects of hydrostatic pressure, allowing it to measure true temperature.
- Unprotected Reversing Thermometer: A type of reversing thermometer exposed to ambient pressure, whose reading is used in conjunction with a protected thermometer to calculate depth or correct for pressure effects.
- Bathythermograph: A related, earlier instrument for recording temperature versus depth, but without the locking/reversing feature of a true reversing thermometer.
- Deep-sea thermometer (a more general, descriptive term)
- Oceanographic thermometer
The term reversing thermometer refers specifically to the instrument with the mechanical locking feature. It is not a general term for any thermometer used in water or one that can measure in reverse order. Its primary and almost sole meaning is within the context of hydrographic and oceanographic data collection.
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a thermometer that registers the temperature in deep waters
