| 摘要 |
<p>PURPOSE:To switch the measuring range without disconnecting the power supply to an object to be measured by providing a shortcircuiting circuit to a series circuit of a direct current ammeter and an opening/closing switch, and providing a shortcircuiting switch in the shortcircuiting circuit. CONSTITUTION:A direct current ammeter 11, an inner resistor 12 and an opening/closing switch 13 which is opened when the measuring range is changed are sequentially connected in series between an input and an output terminals 14, 15. A shortcircuiting circuit 18 is provided in this series circuit. The circuit 18 is provided with a shortcircuiting switch 19 which is closed beforehand when the measuring range is to be changed. Moreover, current resistances 17a-17n different in resistance from each other are connected in parallel to the series circuit through a change-over switch 16 which is interlocked with the switch 13. When the measuring range is changed, the SW 19 is closed to close the circuit 18, thereby ensuring the power supply route to an object to be measured. Thereafter, the SW 13 is opened to open the circuit of the ammeter 11, and the resistors 17a-17n are selected by the SW 16 so that the desired measuring range is obtained. After the measuring range is changed, the SW 13 is closed to close the SW 19, so that a target current is measured.</p> |
