| 摘要 |
PURPOSE:To accurately detect the concn. of dust by keeping the amount of air supplied to a dust detector almost contact by absorbing the variation in the flow speed or static pressure of a dust-containing air stream by the increase or decrease in the amount of air leaked from the open part of an interference chamber. CONSTITUTION:If the clogging degree of a filter 1 becomes high, the static pressure at the opening end of a suction pipe 5 becomes slightly high. The variation in a flow speed or static pressure exerts effect on the sucking amount of air by a fist suction fan 11 but the fan 11 always sucks air in an amount equal to or more than that of air to be supplied to a dust detector 12 and allows excessive air to leak from an opening 13 in an interference chamber 10 and the variation in sucked air due to the variation in the air stream within an exhaust unit 2 is absorbed by the increase the decrease in the amount of air leaked from the opening 13 and the pressure in the interference chamber 10 becomes almost constant. Therefore, a constant amount of air is supplied to the detector 12 by the steady rotation of a second suction fan 18. By this method, the amount of sampled air supplied to the detector 12 is always kept constant at the time of the variation in the flow speed of dust-containing air and the concn. of dust can be accurately detected. |
