is also the most important part of an experiment.
Measuring is not
as it does not deFne a quantity (standard) to be measured.
Measuring is a
effort and is made to compare and to evaluate. To be indepen-
dent, a comparison requires a
a standard unit.
The art of measuring is at least as old as humanity itself. The human body performs
measurements all the time. One of the most basic quantities continuously measured by
the human body is the environment temperature. ±eeling
is a consequence
of this measuring. Although not descriptive (not quantiFed with a parameter such as
temperature), the natural measuring of the environmental temperature by the human
body is nevertheless a relative process. This process is based on a comparison of the
environmental temperature with a certain standard, in this case the temperature at
which the body feels neither hot nor cold—the
of human thermal control.
In heat transfer, temperature and heat ﬂow are unquestionably the most important
quantities to be measured. Other quantities of interest to heat transfer include ﬂuid
speed, pressure (force), mechanical stress, electric current, voltage, length, surface
area, volume, and displacement. In this chapter the focus is on temperature and heat
General measuring concepts such as
sensitivity, hysteresis, calibration, accuracy,
are presented Frst. Then the discussion turns to statistical concepts
mean, deviation, standard deviation, normal distribution, Chauvenet’s crite-
related to the determination of precision, bias error, and
measuring uncertainty. The Fnal section of this chapter is devoted to a brief discussion
of some common instruments for measuring temperature or heat ﬂow.