How does a digital thermometer work without mercury?
Answers
Answer:
Mercury thermometers are based upon the practical phenomena that mercury expands with temperature. A small amount of mercury in a reservoir is subject to heat and it expands and pushes the mercury up a capillary (thin) tube so we can easily see the expansion against a physical scale. Mercury is used, because mercury stays a liquid over a wider temperature range than water - a water-based thermometer won't work once it freezes and as such would be useless in many parts of the world in winter. Alcohol is sometimes also used.
One drawback of mercury theremometers is that they are visual - you can only read it with your eyes conveniently. They are hard for computers to read and display.
With electronics, if you want to measure temperature you need a sensor or transducer as we prefer to call them that changes electrical properties with temperature. There are actually many ways to do this - we have thermocouples that put out a small microvoltage voltage proportional to the temerpture, we have RTD which change resistance, we have semiconductors in which the V/I curve is a function of temperature. We can also measure the infrared signal strength off a surface for non-contact measurement. The trick then is to get the analog electrical phenomena converted to a analog voltage and then use an analog-to-digital conversion to display the value which has to be properly scaled to the units system or send to a computer.
Explanation:
Answer:
digital thermometer contain a device called thermoresister.