Thousands of people in the UK take their own weather observations every day; many enthusiasts in fact try to forecast the weather themselves. One of the most valuable tools for forecasting is a barometer, so you can see how the pressure is changing.

Different levels of pressure have different weather conditions associated with them and forecasters can use these different readings to work out how areas of low and high pressure will affect places as they move. Before you can use your barometer, however, it needs to be set correctly.

Aneroid barometers are the most common used in homes. It simply measures the expansion and contraction of an airless metal box as pressure changes. As the pressure changes, a pointer on the front of the device moves illustrating the change on a dial.

Pressure can be measured through a number of scales, but the most common, and that used by the BBC, is millibars. However, pressure can also be calculated in Pascals or inches of mercury and you can convert those into millibars by using our Pressure Calculator.

If you want to compare your readings to those used by professional meteorologists, you will need to adjust your barometer so it takes a reading as if at sea level. This is because atmospheric pressure varies as you get higher, so different readings will be taken the higher you live above sea level. BBC forecasts, newspaper forecasts and other media use readings adjusted as if they were taken at sea level. Principally it is the change in pressure which is most useful, rather than the actual figure anyway.

The best day to set your barometer is on a day with anticyclonic conditions when the pressure level won't change too much. A typical day would be when there is little wind and conditions are perhaps clear or sunny. On such a day, phone your local weather centre and ask for a current pressure reading. If you can't track the weather centre down, phone the Met Office's customer centre (0845 300 0300) and they should be able to assist.

Most aneroid barometer's have a little screw on the back of them and this is how your set the reading, however make sure you check the instructions of your particular instrument.

Once your barometer is set you'll be able to take your own readings and see for yourself changes in atmospheric pressure, a valuable tool in weather forecasting.

Related Articles:

- My Weather Station - Advice and tips on taking weather
- Observations at home
- Pressure Calculator