Six's thermometer

A minimum-maximum thermometer according Six (also maximum-minimum, maxima minima or maxima minima thermometer ) is used to detect in a longer period of time ( minutes, hours or days) the minimum and maximum temperatures that occur at the same time display the current temperature.

Construction

The minimum-maximum thermometer ( old type ) consists of a long U-shaped glass tube, in which ethanol / contains mercury. The mercury collects in the bottom of the U, and running temperature changes relatively far up the left and right legs of the U. On the left and right ends of the mercury column magnetic float, colored float ( drive pins ). Also located in the left leg of the U-shaped tube, a transparent liquid medium having a high coefficient of expansion, for example, ethanol. This liquid medium is the actual measuring liquid. On the left leg there is a temperature scale above the deepest and below has the highest temperature values ​​. On the right leg however, it is vice versa. The scale starts down there with the lowest temperature values ​​and ends up with the highest temperatures. In the right leg of the U is located with the mercury, a gas that exerts a slight pressure on the continuous column of mercury. This gas pressure can push back the mercury column at decreasing temperatures in the left leg.

Example of a measurement

If the temperature rises, the liquid medium to be measured extends from above the left leg. Because the diameter of the capillary tube is greater than that of the steel rods, flows around the newly created additional volume of alcohol the left tow pin, so he will not be moved but is detained by a lying behind the scale permanent magnet. The ethanol suppresses the left leg of the U - tube, the mercury column down the right leg facing up. The mercury pushes the right tow pin in front of it up to the highest temperature is reached. He is being held at the maximum value of a permanent magnet. The position of the right tow pin shows the highest temperature reached.

When the temperature drops, then reduces the volume of liquid to be measured, the measuring medium becomes a bit together and sucks the mercury again higher in the left leg of the U - tube. Media measured between the left column of mercury and the left tow pin flows around the left tow pin and flows upward. Because of its large surface tension of the mercury can drag the pen does not flow around, but pushes him with decreasing temperature before them upwards to the lowest temperature is reached. A permanent magnet holds the tow pin in this position. The position of the left tow pin shows the lowest temperature reached.

At temperatures between these two extreme values, the mercury, the drive pins are no longer touched. The maximum and minimum temperature of the observation period is indicated by the positions of the magnetic held tow pin. The actual temperature can be read at the ends of the mercury on the scales.

To restart an extreme value measurement, the thermometer is supplied with a push button, which is located between the two legs of the tube, reset. This has the consequence that the permanent magnets are slid rearwardly. Thus, the drive pins are no longer attracted to and fall respectively on one end of the mercury column. If the push button is released, the magnets come forward again and can drive pins on hold again. The thermometer is now ready for use.

Interior

The picture shows a decomposed minimum-maximum thermometer conventional design. On the right you can see the glass tube. It consists of the U- shaped central portion with the capillary in which the mercury and the display pins are and the two pear-shaped extensions above. The tube is inserted in a support made of plastic on the scale is printed in degrees Celsius. The tube has been adjusted down with glue and calibrated. Under magnification, the glass bulb A are on the red highlighted area (right) clearly visible and B (left). B contains the measuring liquid that expands when the temperature increases. The glass bulb A is only about half filled with liquid, above is a gas cushion. A acts as a pressure compensator. With decreasing temperature, the gas pushes the mercury thread more in the left capillary. In the center of the image, the rear wall is visible. It carries a spring plate on which two permanent magnet strips are glued. These magnetic strips hold the small display pins if this plate is directly behind the U- tube. To reset the thermometer, this plate is pushed back briefly. (To show that the strips are magnetic, liable in the picture a paper clip on it. ) On the left is the case can be seen from plastic. The plate with the U- tube is inserted therein, and the thermometer is then closed to the rear wall.

The thermometer indicates a current temperature of 19 degrees Celsius, a minimum of 6 degrees and a maximum of 29 degrees.

Because of the dangerous mercury those thermometers are manufactured according to EU regulations only for commercial use. Otherwise, these are produced now mercury-free. Alternatively, there are those today in digital, electronic and bimetal construction.

• Thermometer