Sometimes TV news has little thermometer pictures or temperature displays in the corner of the screen that persist throughout the channel's news,
weather and sports broadcast. It might look something like this one on the left.
Why? Because temperature is usually what people care most about in the weather report.
How warm it is now or will become shortly. These kinds of television thermometer pictures usually display one value only, but many real indoor and outdoor thermometers have more than one. Usually two of the three scales in this picture.
Which one is Fahrenheit? The third temperature scale on the right; on that scale, comfortable outdoor temperatures range from a cool 60 degrees (°F)
to a warm 75 degrees or more. Below 50 is a fairly cold day; water
freezes at 32.
Above 80 is usually considered hot weather while water boils at 212. See additional examples in the drawing.
To change from Fahrenheit to Celsius, add 40, divide by 9, multiply by 5, subtract 40. Easy.
A capital C at the top of the drawing marks the second temperature scale in the image. The same comfortable outdoor temperatures are now expressed on a scale from a cool 15 degrees (°C) to a warm 24. Below 10 is a blast of cold air, and water freezes at zero.
Above 27°C is considered hot weather in many regions and 100 is the boiling temperature water usually has at sea level.
Because of this freeze-at-zero / boil-at-a-hundred attribute, the Celsius scale is also known as centigrade, where centi means hundred.
For a more technical description, I have included two lighthearted but scientific articles that give you a good amount of detail on the history and development of the various temperature scales. They mention nearly a dozen different scales in total.
1) Numerous scales
2) The invention of Fahrenheit and Celsius
And now about Kelvin...The far left scale on the thermometer pictures above (with a K) is simply the Celsius temperature plus 273 or so. We call it the Kelvin scale, and is based on the fact that the so-called absolute zero, the coldest temperature possible, is roughly equal to –273.16 on the centigrade scale. There is another absolute scale called Rankine, and it is simply degrees Fahrenheit minus 459.69.
Here is a technical definition meteorology people use for temperature: The temperature of a body is one condition that determines its ability to transfer heat to other bodies or to receive heat from them.
Heat flows downhill in relation to temperature. In other words it flows from the warmer object "downhill" towards the cooler one, and the greater the temperature difference, the steeper the hill and the faster the heat flow. Want to know more about weather and temperature?
3) What's one special name for an unusually warm period in the middle of winter?
How to get the best from your own thermometer: The location of the thermometer is very important. Direct sunlight heats the thermometer, and nearby buildings can be a source of heat.
Both of these circumstances give falsely-high temperature readings, and direct sunlight has the greatest effect.
At night the temperature right on the ground can be several degrees colder than the air even a few feet above ground at eye level. Meteorologists use standards for consistency. To obtain official readings, technicians install temperature recorders on the north side of a building, but not too close, or north of a tree and about six feet from the ground.
Better yet. They house the thermometers and other meteorological instruments in an enclosure called a Stephenson Screen.
Strange uses for thermometer pictures: Why do charity campaigns, fundraisers and blood drives use large hand drawn pictures of thermometers to show progress? Like this one on the right for instance...
Probably because we have some emotional connection with this sight.
It graphically demonstrates how much progress has been made and how much
remains for their project. And observers can easily compare progress
with the goal.
Special applications use advanced thermometer pictures and designs, such as infrared thermometers and digital remote thermometers.
For enhancing your home and garden, combinations such as thermometers with humidity displays or outdoor clock and thermometers are popular and people enjoy their convenient displays.
The most common thermometer pictures show one with a glass bulb full of liquid (such as mercury ether or alcohol), which expands and rises into a vertical tube marked with a scale showing the temperature in °F, °C or both.
You might even see a special apparatus such as this one on the right in some unusual thermometer pictures.
An electronic temperature sensor, a thermometer used in these temperature-humidity data loggers, is put into an electrical circuit as a resistor. The electrical resistance of this component changes as the temperature changes.
Here’s an unusual example. My wife got me a Galileo Thermometer one Christmas, like the one in this photo. The glass balls do not change in size, but the liquid they float in becomes lighter when warmer. This causes them to slowly drop when it warms up. Click on the photo for a fuller explanation.
One more type of thermometer: a bi-metal strip thermometer is a clever one.
Indoor thermometer pictures and garden thermometers such as this one on the right employ this type of sensor mechanism used in some household thermostats, a device that keeps temperature steady inside your house. All metals expand when heated, but at different rates.
Inside the device shown, manufacturers stick two strips of metal together and make a coil out of it. When the whole thing heats up, one of the metals expands faster than the other and the loop becomes tighter.
In other words it curls even more. If you were to attach a needle to this apparatus you could add a visible scale so the needle points to the correct temperature, just like they have done here.
Wanna talk a bit about thermometers?
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