| 摘要 |
PURPOSE:To enable the operation at a low power source voltage by reducing the voltage drop across a resistance for detection of current in a constant current pulse drive circuit for driving an ammeter for indicating revolutions. CONSTITUTION:When a pulse signal with a fixed pulse width having a frequency proportional to the engine revolutions is applied to an inverter 33, a Darlington transistor 13 is turned ON or OFF and an ammeter 5 indicates the revolutions by an average current. A resistance 14 is provided to detect current flowing through the ammeter 5 when the transistor 13 is tunred ON to effect a control so that a fixed current flows through the ammeter 5 with transistors 25, 28 and 31 when the Darlington transistor 13 is turned ON. |
