Max Min Thermometer
Max min thermometers are registering devices that are used to record the minimum and maximum temperature at a certain location over a period of time. Widely used in weather stations, cold storage rooms, construction industry and also in horticulture, the max min thermometers are available in both analog as well as digital styles.
The max min thermometer was invented in the year 1780 and apart from some minor tweaking, the same basic design is still used. Although one notable difference in modern max min thermometer construction has been the replacement of mercury by some other fluids. This happened due to a growing realization about mercury being poisonous and also harmful to the environment.
Max min thermometers indicate the current temperature and also the highest and lowest temperature since last reset simultaneously. These are affordable, very accurate, long lasting and highly reliable.
Max min thermometers generally have one long U shaped tube. There is a bulb containing alcohol at the top of the tube. As the temperature changes, the alcohol expands or contracts pushing the indicator liquid or mercury, thus showing the temperature.
For recording the maximum and the minimum temperature, two steel pins on the right and left hand column are also there. When the temperature rises, the right hand column marker pin is moved. When the temperature falls, the marker pin in the left hand column is moved. Both the pins will stay there unless the thermometer is reset.
Buying Instructions :
While buying a max min thermometer, make sure that the indicator liquid does not have any gaps in it
Also make sure that the steel pins on the right and left hand columns are not buried in the indicator liquid
Ensure that the glass parts of the thermometer aren't cracked or broken
Try and buy a max min thermometer that does not use mercury for indicating temperatures
Max min thermometers are delicate, so these must be handled with due care
The thermometers should periodically be calibrated so as to ensure consistent and optimal accuracy
The thermometers should be wiped occasionally with a clean cloth to remove dust from their glass surface
The horizontal position and vertical position readings of max min thermometers should be compared periodically. If the difference between both readings is more than 0.2 degrees, it means a breakage in the liquid column has occurred. Such thermometers cannot be repaired and should be replaced.