For this experiment, a PWM signal with a 60%
duty cycle is used for pulse heating. Fig. 9 shows the current consumption
profile, which decreases in the range from 0 to 900 ms
(760 ms) as the sensor is heated up. Because of the duty cycle,
the average heating current for the sensitive layer is only about
80 mA. If an emergency event occurred, the message is transmitted
to the network coordinator. The average current consumption
in data transmission mode, shown in the graph in the range from
1000 to 1500 ms (347 ms), is 40 mA. Fig. 9 shows that the pulses
of data transmission do not affect the average current consumption
much. Besides, the data transmission occurs only in the case
of an alert. Therefore, we may neglect the current consumption in
data transmission mode for the purpose of computing the average
current consumption. The average current consumption, ¯I, may be
determined with the formula: