| 摘要 |
PURPOSE:To obtain total operation hours which are conerted into the total operating hours of the device under a preset temperature, by changing the counting speed in response to the difference between an environmental temperature and the preset temperature, and monitoring the temperature stress of the device even under the state of the variable environmental temperature. CONSTITUTION:The output of a temperature sensor 1 is linearized 2 and compared 3 with a preset voltage e(TO) corresponding to a reference temperature TO. The output voltage corresponding to the difference is fed to an exponential amplifier 4, thereafter converted into a frequency by a V-F converter 5, and inputted to a counter 6. When the environmental temperature T is larger than the preset temperature TO, the counter 6 expedites the counting. When T is smaller, the counting is delayed. Therefore, even though the environmental temperature is changed into any values, the hours corresponding to the case, wherein the operating hours of the devices are assumed to have been elapsed under the preset environment, can be found. |
