TCi Operator Manual
98
Note: to minimize
C
one needs to minimize sensor effusivity
.
This is an important conclusion for
the error analysis below.
To calculate the effusivity of the measured materials we solve the polynomial equation (21) for
e
2
:
2
1
2
2
2
2
1
2
2
2
4
/
1
M
M
M
C
M
M
M
m
e
(23)
Where
1/m
is the inverse of the voltage versus
√
t slope measured for this material, and
M
1
, M
2
&
C
are the curve coefficients and intercept of the effusivity calibration curve for that sensor. Use +
if
M
2
0, use – if
M
2
0. If
M
2
=0 than the linear equation (17) applies.
Software cal parameters:
M
2
; M
1
; C. C=C(T)
and is further broken down to
C
0
, C
1
and C
2
as a
function of temperature, see below. Also note that
C
will be different at different power levels.
Range of typical
M
1
= 0.03 – 0.06 (
Amp
W
C
m
2
) for the TCi sensor (depends
on sensor power).
C
= 25 – 60
(
V
s
) (depends on temperature and sensor power).
9.2
Material groups and power levels
The wide range of effusivity and
k
requires grouping of materials with similar behavior and
effusivity/k range, and operation of the TCi sensor at different power levels. Each group of
materials has its own calibration curve, which is of course affected by the power level.
Summary of Contents for TCi
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