| 摘要 |
PURPOSE:To prevent dewing in a pressure detecting unit including a pressure conduit and secure the safety of a combustion instrument by a method wherein a memory unit, into which the saturated steam pressure curve of water is memorized, and a comparating and deciding unit are provided and an electric heater is operated by the signal of a temperature and humidity sensor. CONSTITUTION:The device is provided with the memory unit 20, into which the saturated steam pressure curve of water is memorized, and the comparating and deciding unit 21. When the combustion is stopped and the ambient temperature of the combustion instrument is reduced suddenly, the pressure of steam approaches the dew point thereof gradually. In this case, when the steam pressure is smaller than the saturated steam pressure shown at the dew point in the temperature of that time, an electric signal is not outputted from the comparating and deciding unit 21 into an electric heater driving circuit 22. When the ambient temperature is reduced suddenly due to the sudden change of a weather condition or the like after using the instrument under a circumstance having high humidity and the steam pressure is saturated at the dew point, the output of the unit 21 becomes equal to the same of the memory unit 20 and the electric signal is outputted from the comparating and deciding unit 21 into the electric heater driving circuit 22. According to this method, the electric heater 17, attached to the pressure conduit 15, may be heated only when the ambient temperature of a differential pressure sensor 11 has arrived at the dew point during stopping the operation of the instrument. |
