Environmental Engineering Reference
In-Depth Information
Spring
Bellows
Pressure
figure 4.42 Bellows gauge.
Temperature
has been defined in a variety of ways. One approach
defines temperature as the measure of heat (thermal energy) associated
with the movement (kinetic energy) of the molecules of a substance.
This definition is based on the theory that molecules of all matter are
in continuous motion, which is sensed as heat. For our purposes, we
define temperature as the degree of hotness or coldness of a substance
measured on a definite scale.
Temperature is measured when a measuring instrument (e.g., a
thermometer) is brought into contact with the medium being measured.
All temperature-measuring instruments use some change in a material
to indicate temperature. Some of the effects that are used to indicate
temperature are changes in physical properties and altered physical
dimensions (e.g., the change in the length of a material in the form of
expansion and contraction).
1200
1000
800
600
400
200
Pressure
connection
figure 4.43 Plunger gauge.
