| 摘要 |
PROBLEM TO BE SOLVED: To enhance the measuring accuracy of the impedance of a plasma load or a voltage between peaks, in monitoring of the plasma state of the plasma load. SOLUTION: An impedance conversion circuit 3 is inserted between a power source 1 and a load 5. A voltage detection portion 3A1 for detecting a voltage V1 at the power source side end of the conversion circuit 3, and a current detection portion 3A2 detecting a current 11, and a phase difference detection portion 3A3 detecting the phase differenceθ1 between the voltage and the current are provided. First input impedance computing portion 23c computing an impedance seeing a plasma load side from the power source side end of the conversion circuit 3 as the first input impedance Z1* from the phase difference between the voltage and the current, and a second impedance computing portion 23e for computing an impedance seeing a load side from the load side end of the conversion circuit 3 as the second input impedance Z2* from the constants ZC1*, ZC2*, ZL* of elements constituting the conversion circuit 3 and the first input impedance are also provided. A plasma impedance computing portion 23 for computing a load impedance from the impedance Zs* of a feeding line 4 which connects the load side end of the conversion circuit 3 and the second input impedance is further provided.
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