Thermometer

• The mercury thermometer is designed to measure the temperature of the human body; graduated to cover a range a few degrees on either side of the normal body temperature The thermometer consists of mercury contained in a bulb at the bottom of a graduated sealed glass capillary tube marked in degrees Celsius or Fahrenheit.

Lab thermometer developed during the 16th and 17th centuries, a thermometer (from the Greek (thermo) meaning "warm" and meter, "to measure") is a device that measures temperature or temperature gradient using a variety of different principles.[1] A thermometer has two important elements: the temperature sensor (e.g. the bulb on a mercury thermometer) in which some physical change occurs with temperature, plus some means of converting this physical change into a numerical value (e.g. the scale on a mercury thermometer).

Six's maximum and minimum thermometer is a popular thermometer among gardeners for use in greenhouses. Its purpose is to read the maximum and minimum temperatures reached since the thermometer was last read. Generally speaking a minimum temperature occurs during the night and a maximum during the day. It was invented by James Six towards the end of the eighteenth century, and consists of a fairly large cylindrical bulb full of alcohol, connected by a U- shaped stem to a second bulb nearly full of alcohol or oil of creosote.

This digital thermometer circuit diagram uses a common 1N4148 diode as the temperature sensor. The temperature factor of the diode, -2 mV / 0C is exploited for this application to create an accurate electronic thermometer. To display the measured temperature, a digital multimeter is used and so we can measure temperature values from -9.990C up to +99.90C.