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

6 Temperature Monitoring of the Front End Readout Electronics
C)
°
MCM surface temperature (
50
45
40
35
30
25
20
400 420 440 460 480 500 520
ADC value (a.u.)
Figure 6.12: MCM surface temperatures measured with an IR camera as a function of the corresponding
MCM temperature sensor readings. The straight line is a fit.
a value of 500 corresponds to a surface temperature of 41.8 ± 0.4 °C and a change in
the MCM temperature sensor reading of 100 corresponds to a temperature change of
13.8 ± 0.5 °C.
Due to the variation in the gain factor of the temperature sensors a generalization of
the just obtained result has to be done very carefully. Figure 6.13 shows the averaged
MCM sensor readings of the chamber used for the IR temperature measurement. The first
values of all ADCs were set to zero to eliminate constant offset. Additionally, the sensor
readings of the two MCMs with the highest and lowest values are shown. The error bars
were determined by fitting the distribution of the MCM sensor readings in each time-bin
with a Gaussian function and using the σ of the fit as the error of the corresponding data
point. Therefore all curves show relative changes. The solid black lines are the scaled
temperatures measured with the infrared camera (plot 6.11). The scaling was done with
the linear function
ADC = a · TIR + b. (6.7)
TIR is the temperature measured with the infrared camera and ADC is the scaled value
shown in figure 6.13. The parameters a and b in equation are determined by plotting
the measured temperature as a function of the corresponding MCM sensor readings and
fitting the data like shown in figure 6.4 already. Table 6.2 shows the obtained values for a
and b.
Formula 6.7 can be transposed to TIR. Using the values shown in table 6.2 for a and
b, a change of 100 in the MCM temperature sensor readings corresponds to an surface
temperature change of about 13.3 °C for the averaged plot, to a temperature change of
9.2 °C for the low MCM and to an temperature change of 15.3 °C for the high MCM.
Taking all obtained results into account, the final result is that a change in the MCM
temperature sensor readings of 100 corresponds to an surface temperature change of
about 13 ± 2 °C. An absolute calibration of the MCM sensors remains not feasible.
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