3.5 Design of accelerated testing

According to the failure-mechanism in Fig 13, temperature change, which should include 0℃ because of the temperature fluctuation of radiator fin of air conditioner in a car, with moisture is essential. In addition, voltage should be applied to samples.

To find the effective factors to accelerate the failure, "Design of Experiment" was conducted according to Table 2 to 3 and Fig. 14.

　

Table 2 Assignment by Orthogonal Array (L₈)

Table 3 Factors and Levels

T: temperature (℃) H: humidity (%RH )

V: applied voltage (volts) 1,2: level1, level2

　

Fig. 14 Test Circuit

　

The result is shown in Table 4, which suggests "-10℃〜80℃, 95%RH Temperature Cycling with Humidity" is appropriate as the accelerated testing.

　

Table 4 Analysis of Variance

　

3.6 Calculation of acceleration factor

According to Weibull chart in Fig 15 acceleration factor is estimated around 105.

　

Fig. 15 Weibull Plotting

　

4. Design of accelerated testing for gas sensor

　

4.1 Configuration

Fe₂O₃ semiconductor gas sensor is composed of α-Fe₂O₃ gas sensitive sensor element, a heater, explosion-proof net and a pedestal as shown in Fig. 16.

　

Fig. 16 Sensor structur

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