Why is thermistor thermometer used to measure temperatures of children or infants?
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Babies have very limited methods of communicating what they want or what is wrong with them. Crying can mean any number of different things. At this point, I am fairly good at figuring out when my daughter is tired or hungry or upset about strangers or just bored. However, sometimes she just cries and gets very upset for no clear reason and it is difficult to figure out what is wrong.
A couple of weeks ago, my daughter was very fussy and needier than usual and just refused to nap. After a while, I decided that there was definitely something wrong and that she seemed sick. One of the main tools for determining if our child is sick is our thermometer. Being a scientist (or a geek, if you prefer), I am of course interested in how different thermometers work and how they measure my daughter’s temperature.
While it seems that there are a wide variety of baby thermometers – ear thermometers, rectal thermometers, under arm thermometers and forehead thermometers – the most common types fall into just two categories of operation. The rectal and under arm thermometers use contact between the skin and a metal component on the thermometer to read temperature while the ear and forehead thermometers use the radiation emitted by your baby’s body to calculate temperature. These thermometers use very different techniques to measure temperature than the bulb thermometer many of us grew up with.
Contact Sensors
The metal contact sensors are most commonly electrical sensors. There is a thermistor in the metal detector portion of the thermometer. This is a resistor that changes its resistance depending on temperature. To understand how this works, we need to think about some simple electronics.
Consider a very simple electronic circuit like the one below:
A battery provides a voltage – 9 Volts in this picture. A constant current travels around the circuit because there is just a single path through the loop. An ammeter is a device that is used to measure the current – this is a measurement of how much charge passes through that point in a given amount of time.
Ohm’s Law tells us that voltage, V, is related to current, I, and resistance, R, as follows:
So what happens when my resistor is sensitive to temperature? When you put the resistor in contact with your body, it heats up and its resistance decreases. The battery voltage stays constant, so as the resistance decreases, the current through the system must increase. This makes sense, right? If there is less resistance to the flow of charge, more charges will pass the ammeter in a given amount of time.
By measuring this current, and knowing the voltage of the battery, you can easily calculate the resistance of your temperature sensitive resistor using the equation above. The resistance vs. temperature is something that is very well known by the manufacturer, so once you know the resistance, you know the temperature of your baby who is in contact with the thermometer.
The circuit in your thermometer has a few more components, but this basically how it works. And it does all the calculating for you and just displays a temperature.
A couple of weeks ago, my daughter was very fussy and needier than usual and just refused to nap. After a while, I decided that there was definitely something wrong and that she seemed sick. One of the main tools for determining if our child is sick is our thermometer. Being a scientist (or a geek, if you prefer), I am of course interested in how different thermometers work and how they measure my daughter’s temperature.
While it seems that there are a wide variety of baby thermometers – ear thermometers, rectal thermometers, under arm thermometers and forehead thermometers – the most common types fall into just two categories of operation. The rectal and under arm thermometers use contact between the skin and a metal component on the thermometer to read temperature while the ear and forehead thermometers use the radiation emitted by your baby’s body to calculate temperature. These thermometers use very different techniques to measure temperature than the bulb thermometer many of us grew up with.
Contact Sensors
The metal contact sensors are most commonly electrical sensors. There is a thermistor in the metal detector portion of the thermometer. This is a resistor that changes its resistance depending on temperature. To understand how this works, we need to think about some simple electronics.
Consider a very simple electronic circuit like the one below:
A battery provides a voltage – 9 Volts in this picture. A constant current travels around the circuit because there is just a single path through the loop. An ammeter is a device that is used to measure the current – this is a measurement of how much charge passes through that point in a given amount of time.
Ohm’s Law tells us that voltage, V, is related to current, I, and resistance, R, as follows:
So what happens when my resistor is sensitive to temperature? When you put the resistor in contact with your body, it heats up and its resistance decreases. The battery voltage stays constant, so as the resistance decreases, the current through the system must increase. This makes sense, right? If there is less resistance to the flow of charge, more charges will pass the ammeter in a given amount of time.
By measuring this current, and knowing the voltage of the battery, you can easily calculate the resistance of your temperature sensitive resistor using the equation above. The resistance vs. temperature is something that is very well known by the manufacturer, so once you know the resistance, you know the temperature of your baby who is in contact with the thermometer.
The circuit in your thermometer has a few more components, but this basically how it works. And it does all the calculating for you and just displays a temperature.
Answered by
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HEY MATE HERE IS YOUR ANSWER:-
Thermistor is a highly temperature sensitive device. It's resistance changes very much with change in temperature.
HOPE IT HELPS
Thermistor is a highly temperature sensitive device. It's resistance changes very much with change in temperature.
HOPE IT HELPS
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