Parts of Clinical Thermometer And How to Disinfect Thermometer?

Clinical or Medical Thermometer 


A medical thermometer/ clinical thermometer is a device that is used to measure the temperature of a body.

A glass thermometer consists of; a stem (long part) and bulb (containing a small amount of mercury).

Vital signs help detect or monitor a basic health conditions. The Vital signs include; TPR (Body Temperature, Pulse, Respiration) and BP.


Parts of Thermometer


The parts of the clinical thermometer are 

Parts of Clinical Thermometer

1. Stem

The stem is a longer part of the glass thermometer.


2. Mercury Bulb


The bulb of the clinical thermometer is spherical in shape to store the mercury and is usually made of stainless steel.

The bulb is the lowest part of the glass thermometer, which acts as a reservoir to hold mercury.


It contains a small amount of mercury. Mercury is a metal, at the ordinary temperature, it is in liquid form. Mercury expands in response to heat.

 If the temperature is high then mercury in the bulb moves up the capillary tube.

Mercury leaves the bulb, when the temperature rises and when the temperature descends, the mercury returns to deposit inside the bulb.


3. Capillary tube


The capillary or stem is the tube of the mercury thermometer through which the mercury flows.

The capillary tube is present inside the glass thermometer, and it is connected to the bulb.

The capillary tube is the long cylindrical tube in a mercury thermometer that is connected to the bulb.

When the temperature rises up, the mercury flows up the capillary.

Where capillary tube ends, after that section known as the expansion chamber.


4. Expansion chamber


The expansion chamber of the mercury thermometer is found at the top of the capillary.

The expansion chamber function is to form a larger volume. If the maximum temperature scale is exceeded, then through which the mercury can fill.


5. Scale lines


Scale line in thermometer is divisions of equal length (degrees) marked on the thermometer that indicate the units of measurement. It depends on the type of thermometer that can have ° F or ° C.  

When the temperature increases, the mercury inside the bulb rises and when cool, it goes down.  

Scale line shows how far the mercury rises and goes down, marks on the body of the thermometer indicate the temperature level.


Know here normal body temperature range.


6. Constriction


Constriction in the thermometer prevents mercury from backflow into the bulb when the reading is being taken.

The constriction part is narrower than the stem; it causes the mercury to slow down and gives the user the necessary time to read the temperature reached.


Check out here parts of Stethoscope.


Types of Thermometer


There are different types of thermometer are- 


1. Digital thermometers

2. Ear (or tympanic) thermometers

3. Infrared thermometers

4. Strip-type thermometers

5. Mercury thermometers

6. App-based thermometer

7. Pacifier thermometer



1. Digital thermometers

Digital thermometers work by using heat sensors that determine body temperature and display reading numerically on the digital screen.

Digital thermometers can be used to take temperature readings in the mouth, rectum, or armpit.

Oral temperature can be measured by either a digital or mercury thermometer.


2. Ear (or tympanic) thermometers

Ear thermometers/ Tympanic thermometers measure the temperature inside the ear canal through infrared ray technology. It is put in the child's ear. 


3. Infared thermometers

Infared thermometers use an infrared scanner to measure temperature.

An infared thermometer can be used on both the forehead and wrist areas.

The forehead thermometer uses infrared sensors to measure the temperature of the superficial temporal artery.


4. Strip-type thermometers

The use of Strip-type thermometers is on the forehead.

A temperature strip/ plastic strip thermometer is a type of thermometer; that contains heat-sensitive material in a plastic strip that changes color to indicate different temperatures.

5. Mercury thermometers


Mercury thermometers are mercury-in-glass thermometers. Do not use mercury thermometers; they can break, releasing small fragments of glass and highly poisonous mercury.

6. App-based thermometer

Smartphone apps use the temperature sensors in the phone to show the temperature near your phone. 


7. Pacifier thermometer

A Pacifier thermometer helps to measure the body temperature in infants. If a baby comes down with a fever it changes color in stages from blue to red, which shows a fever.


Use of Clinical Thermometer


A clinical Thermometer is used to measure the body temperature.


Know the parts of a Sphygmomanometer that are used to measure blood pressure.


How to Disinfection of Clinical Thermometer?


Clean your thermometer before and after you use it with either rubbing alcohol or lukewarm soapy water, then rinse with cool water. The clinical thermometer should keep in a safe place, away from the child's reach.


Disinfection Rule

Less contaminated to more contaminated


Disinfected the thermometer with an alcohol swab or cotton ball dipped in alcohol clean within one stroke.


Before Use


Blub to stem

Disinfected the thermometer with an alcohol swab or cotton ball dipped in alcohol and rubbed Blub to stem within one stroke.


After Use


Stem to bulb

Disinfected the thermometer with an alcohol swab or cotton ball dipped in alcohol and rubbed Stem to bulb within one stroke.

Post a Comment


  1. Please can I know the reasons for the direction of cleaning the thermometer before and after use?