| 摘要 |
PURPOSE:To reduce the time for measurement by holding the limit voltage value for the purpose of protecting an object to be measured, and starting the measurement by changing the voltage from the assigned value. CONSTITUTION:When the output current of a constant current circuit 2 is positive, the voltage value of a variable clamp register 8 is fed into a positive D/A converter 10 by a switch 14, by which a digital value is converted to an analog quantity. This analog quantity is amplified by an operational amplifier 12 by which the assigned value is maintained. When the terminal voltage connected to the object to be measured exceeds the assigned value, the current is absorbed and is clamped to the assigned value. The limit voltage value of a positive clamp register 7 is changed over by the switch 14 and is amplified by the amplifier 12, by which the limit voltage value is maintained. When the terminal voltage connected to the object to be measured exceeds the limit voltage value, the current is absorbed and is clamped at the limit voltage value. For example, when a select switch S1 is changed over to S2 upon ending of measuring of the object to be measured connected to a measuring terminal T1, the voltage of the assigned value is applied to the object to be measured, by which the time for charging a capacitor C0 is reduced. The same holds true of the case when the output of the circuit 2 is genative. |
