| 摘要 |
PROBLEM TO BE SOLVED: To detect a sheet resistance value by use of a low vol.tage power source by providing a voltage application switching means, and applying and controlling voltages independently to a recording sheet and a dummy resistor connected in parallel to the recording sheet. SOLUTION: When a recording sheet 12 reaches a position just before it passes a metal roller 13, a controller 16 transmits a switch control signal 17 to short-circuit the switch S1 of a voltage application switching means 15 and release the switch S2 thereof. Only the resistance R of a dummy resistor 14 is connected to a low voltage power source Vcc. When the recording sheet 12 starts to pass the metal roller 13, the switch control signal 17 short-circuits both the switches S1, S2 of the voltage application switching means 15. The resistance R of the dummy resistor 14 and the resistance rp of the recording sheet 12 are connected in parallel to the low voltage power source Vcc. The output voltage of a current-voltage converting means 18 is transmitted to a resistance value detecting means 19. The resistance value detecting means 19 calculates the resistance value rp of the recording sheet 12 by numerical calculation by use of potential difference, return resistance RF, and the low voltage power sourice Vcc. |
