The FEE Server Control Engine of the ALICE-TRD - Westfälische ...

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6 Temperature Monitoring of the Front End Readout Electronics
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Figure 6.5: MCM temperature sensor data with fitted functions of type f (x) = a1 · e b 1·(x−x0) + a2 ·
e b2·(x−x0) + d (solid lines). Each section was fitted separately. The data are the same
already shown in figure 6.3.
the slope of the curve. Parameter c determines the final value of the function for x → ∞
since b < 0 for all fits in this chapter.
Figure 6.6 shows the fitted curves. But for a cooling overview three fit parameters
for each MCM and each section are still too many. A formula is required which takes the
nine fit parameters as inputs and gives just one number (’score’) which indicate how well
cooled an MCM is.
To deduce such a formula, the temperature curves of each MCM in two complete layers
were fitted. One layer had active cooling and the other one was not cooled. The
distribution of the obtained fit parameters are shown in figure 6.7. In the left column
the magnitude is shown as a function of the slope and in the right column the magnitude
is shown as a function of the limit. The linear dependence between the magnitude
(parameter a) and the limit (parameter d) is expected.
As described above, x0 is chosen to fulfill x − x0 = 0 for the first x of each section.
For this value equation 6.2 simplifies to f (x) = a + c. Therefore a linear dependence
between a and c just means that f (x) has the same value for all MCMs at the beginning
of the region. In particular the fit parameters for region one have to show this linear
dependency since the first MCM temperature sensor reading of all MCMs was set to zero
(see begin of this section).
The plots in figure 6.7 show that uncooled MCMs always have a larger absolute value
of a · b. After some tests it was decided to use the following formula to calculate the
’score’:
score = 50 · a1 · b1 + 10 · a2 · b2 − 20 · a3 · b3. (6.3)
a1 and b1 are the fit parameters obtained by fitting the function 6.2 in region 1, a2 and
b2 are the fit parameters from region 2 and a3 and b3 are the fit parameters from region
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