| 摘要 |
<p>An electrophotographic system includes a corona-charging device (10) for applying a charge to a surface and having a coronode (12) driven to a corona-producing condition; a conductive grid (16) interposed between the surface to be charged and the coronode, the conductive grid having a self-biasing arrangement to control the voltage thereon produced by corona current from the coronode, the self-biasing arrangement including a current-sink device between the conductive grid and a common lead; and a power supply takeoff, electrically connected between the conductive grid and the current-sink device, and having a voltage thereat controlled by the current-sink device. An electrostatic voltmeter (100) drivable by such an arrangement includes a probe for detecting voltage on a surface and producing a representative voltage signal; a low-current, high-voltage supply such as that available at the conductive grid; a constant current source (102); a current-sink device connected to the constant current source and having a constant voltage drop thereacross, and providing first and second floating voltages and a relative common lead therebetween; and a voltage controller variably controlling the voltage level at the current-sink device in response to the representative voltage signal; a signal-processing device for conditioning the representative voltage signal for variably controlling the voltage controller; an amplifier (208) driven by the first and second floating voltages.</p> |
