bulb. There are many ways to measure temperature. Some digital thermometers use a
coiled strip composed of two kinds of metal, each of which conducts heat differently. As the
temperature rises and falls, the coil unfolds or curls up tighter. Other modern thermometers
measure infrared radiation or electrical resistance. Modern thermometers usually produce
digital data that can be fed directly into a computer.
Meteorologists usebarometersto measure air pressure (Figure16.38). A barometer may
contain water, air or mercury. Like thermometers, barometers are now mostly digital. Air
pressure measurements are corrected so that the numbers are given as though the barometer
were at sea level. This means that only the air pressure is measured instead of also measuring
the effect of altitude on air pressure.
Figure 16.38: Barometers are Mercury columns used to measure air pressure. ( 13 )