| 摘要 |
PURPOSE:To arrange so that stable detection may be achieved even if the amplitude of a flow speed detection signal were changed, by obtaining a logic product of an output of a flow speed detection signal compared by a comparator for detecting a threshold value and an output compared by a comparator for detecting a zero cross point. CONSTITUTION:Ink droplet flow speed detection signal from an input part 30 is first converted to a direct current through a diode 31, a condenser 32 and a resistance 33, and then is compared with a threshold value indicated by a resistance 34, 35 by a comparator 36. After this process, the signal enters a logic product circuit 40. In addition, a flow speed detection signal is inputted to a comparator 39 through a resistance 37. The signal rises sharply to both positive and negative poles each time it crosses O volt, and reaches a saturation voltage when it falls. A logic product circuit 40 carries out a logic product arithmetic operation of a signal exceeding in value a sufficiently larger threshold value than the noise level of a flow speed detection signal and a signal which does not delay a detection time even if the amplitude of a detection signal were changed. Therefore, it is possible to detect the flow speed stably and control the flow speed of ink droplets stably. |
