| 摘要 |
PROBLEM TO BE SOLVED: To accurately measure a current value of the measurement current, while allowing a resistance value of the detection resistor to be switched.SOLUTION: A detection resistance circuit 6 is constituted of a detection resistor 6a and a detection resistor 6b in which one ends are connected to each other and which are connected in series; and a relay 6c connected in parallel to the detection resistor 6b. The other end of the detection resistor 6a is connected to the other end of a negative feedback coil 4, and the other end of the detection resistor 6b is connected to a reference potential G. An amplifier circuit 7 includes: an arithmetic amplifier 7a, an input resistor 7d connected between the other end of the detection circuit 6 a and an inverting input terminal of the arithmetic amplifier 7a; an input resistor 7e of which one end is connected to one end of the detection resistor 6b; an input resistor 7f of which one end is connected to the other end of the detection resistor 6b; and a changeover switch part 7g making the other end of the input resistor 7f connect to a non-inverting input terminal when the relay 6c is shifted to an off state. |
