| 摘要 |
PURPOSE:To detect the level of powder such as a toner in a short time without lowering precision by detecting the level within a fixed period of time after power is supplied to a detecting element rising in temperature by feeding power. CONSTITUTION:Once transistor TS conducts by a control signal, thermistors Thm1 and Thm2 forming detecting elements provided in the air and toner rise in temperature with power fed. Since thermistor Thm2 is large in heat emissivity through the toner, its rise in temperature lags that of thermistor Thm1 and operational amplifier OP generates output ''1'', so that the powder such as the toner will be detected being higher than a fixed level. In this case, limiting the control signal applied to transistor TS so that the conduction period of transistor TS is 60 seconds makes it possible to detect whether the pulverulent body being lower or higher than the fixed level in a short time before thermistors Thm1 and Thm2 reach constant temperatures without lowering precision in transient response. |
