The instrument used to measure temperature is usually the thermometer, although a thermistor can also be used. Learn about the way in which a thermometer works on the basis of liquid expansion with help from a science teacher in this free video on physical science.
Hi. I'm Steve Jones, and I'm going to explain what kind of instruments are used to measure temperature. Well, what kind of instrument is used to measure temperature? Well we would say straight away, a thermometer. But this isn't the only instrument used to measure temperature. Although many of the other instruments could also be called thermometers. Because thermo is heat meter, so it's a temperature meter. A thermometer is, works on the basis of the expansion of a liquid. The liquid is usually mercury or alcohol. And those are the two that are commonly seen, mercury and alcohol, in a thermometer. There are other ways though. You've got a thermistor. A thermistor is an electronic device which changes temperature and when it changes temperature it changes resistance. So changing some kind of physical property is important to measure temperature. So, if something increases when the temperature increases, you can use it to measure temperature. Another one is the pyrometer. If you've got very, very high temperatures, temperatures if you, for example if you put a thermometer in it, it would actually melt the thermometer. Or if you put a thermistor in, it would melt the thermistor. You can't measure those high temperatures using a conventional thermometer. You have to have something else. And the pyrometer is a device which looks at the spectrum. Looks at the light coming from the object. And the light spectrum is like this and along here we're measuring wave length, and up here the intensity and what we can have here, is a, is a scale in degrees Celsius, and that will tell us exactly what the temperature of the particular material is. This is used in furnaces, this is used to determine the temperature of the sun for example, and so forth. We can look at this and we can tell what the temperature is by looking at the spectrum. So these are all possible ways of measuring temperature. You might have seen something like this occasionally, used by a potter. And he will have a series of little pottery towers and this one is 650 degrees Celsius, and this one is 645 degrees Celsius. And these are the temperatures at which these things melt. And as soon as this one goes like that, into a heap, then he knows it is more than 645, and as long as this one is still standing, it's less than 650. And this enables him to get an approximation of the temperature of the furnace, of the kiln for example in which he's firing pots. So it doesn't get too hot, it doesn't get too cool. He'll take it to the right temperature, and keep it there. So basically, that is what device is used to measure temperature, which devices. They're all thermometers, but there are a lot of different types.