Theory:

In hospitals/clinics, you might have seen the doctors or nurses using the device to measure the temperature.

What is it?
It is Thermometer - The device which is used to measure temperature is called a thermometer.
A thermometer has two essential elements:
  1. A temperature sensor - Used to detect changes in temperature
  2. Element which is used to convert the temperature changes into a numerical value
Clinical Thermometer
The device which is used to measure the temperature of our body is called clinical thermometer.
Structure of Thermometer:
  • The thermometer has a long narrow tube with the same thickness throughout the length.
  • On one side of this tube, a bulb contains mercury which acts as a temperature sensor.
  • There is also a scale on the thermometer for reading the temperature
  • All clinical thermometers have a very fine capillary tube that originates from the bulb. When there is a rise in temperature, mercury expands through this tube.
  • The capillary tube has a bend near the bulb known as kink, which blocks the mercury from returning back into the bulb when the thermometer is taken out of the patient’s mouth or armpit.
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Fig. - Clinical Thermometer
Important!
The normal temperature of human body is \(37\)°\(C\) / \(98.6\)°\(F\). However, it can vary between \(35\)°\(C\) to \(42\)°\(C\) / \(94\)°\(F\) to \(108\)°\(F\). Therefore, the clinical thermometer has reading from \(35\)°\(C\) to \(42\) °\(C\) / \(94\)°\(F\) to \(108\)°\(F\).
Temperature Scale in Clinical Thermometer:
There are temperature scales on either side of the mercury thread, one in Celsius scale and the other in Fahrenheit scale. Since the Fahrenheit scale is more sensitive than the Celsius scale, body temperature is measured in °\(F\) only.
 
Important!
Precautions to be followed while using a Clinical Thermometer:
  • Handle the thermometer with care.
  • The thermometer should be washed before and after use, preferably with an antiseptic solution.
  • Jerk the thermometer a few times to bring the level of the mercury down.
  • Before use, the mercury level should be below 35°\(C\) or 94°\(F\).
  • Do not hold the thermometer by its bulb.
  • Keep the mercury level along your line of sight, and then take the reading.
  • If it hits against some hard object, it may break.
  • Do not place the thermometer in a hot flame or in the hot sun.