Fig. 2
From: Analysis of passive calorimetric probe measurements at high energy influxes
Calorimetric probe measurement for the energy influx of an atmospheric pressure plasma jet. The jet was operated with a voltage of 300 V (primary power 2.3 kW), a frequency of 19 kHz, 30 slm nitrogen and at a distance to the probe of 6 mm. The measurement frequency was 100 Hz and the energy influx was determined to 433 ± 2 W/cm2. a shows the temperature evolution over time with an exponential fit. The exponential fit corresponds to the linear fit between P2 and P3 of b. b shows the relation between the temporal derivation of the temperature and the temperature for the same measurement. Different phases can be distinguished. P1 marks the start of the heating, where the shield for the warm-up time was removed from between the plasma jet and the probe. P2 is the point where the full power is applied to the probe. The surrounding starts to heat up around P3 and the measured curve deviates from the fits (linear and exponential). The plasma jet was turned off at P4 and the transition to the cooling phase was completed around P5. The dashed line marks the equilibrium temperature and the intersection between this line and the linear fit (P6) gives the value for the linear method to obtain the energy influx. c shows the part for the linear fit in more detail. It can be seen that the measurement frequency is sufficiently high and the linear fit is in good agreement with the data