| 摘要 |
PROBLEM TO BE SOLVED: To report noise intrusion into an internal circuit in real time without affecting a power supply and a signal.SOLUTION: A series connection circuit of a capacitor C1 and a lamp 4 are connected between a signal line L2 and a frame earth FG, as a noise detection circuit 5. The capacitor C1 has the same capacity as a varistor 3 (3-1, 3-2). If noise NZ is generated between the signal line L2 and the frame earth FG and the frequency of the noise NZ overlaps the resonance frequency of a capacitive coupling of the varistor 3-1, the noise NZ intrudes into an inner circuit 1 through the varistor 3-1, while the noise NZ intrudes also into the capacitor C1 having the same capacity as the varistor 3-1. Thus, a current (noise current) flows through the capacitor C1, the lamp 4 is lit by the current, and the intrusion of the noise NZ into the internal circuit 1 is reported.SELECTED DRAWING: Figure 2 |
