
28 Fundamentals of Sensors for Engineering and Science
the sensor resistance, h
sf
is the convective heat transfer coefficient for the
sensor and the fluid, A
s
is the surface area of the sensor over which heat
is transferred to the fluid, T
s
is the sensor temperature, and T
f
is the fluid
temperature.
The potential difference across the sensor is related to the output voltage
of the bridge circuit, E
o
, by
E
s
= E
o
R
s
/(R
s
+ R
o
), (2.5)
where R
o
denotes the resistance that is in series with R
s
in the bridge. The
heat transfer coefficient for a small wire or rod is
h
sf
= C
0
+ C
1
p
ρU, (2.6)
in which C
0
and C
1
are constants that depend upon the ambient tempera-
ture, ρ the density