To reduce noises mingling in a signal cable in a weak current signal transmitter, especially an SRNM detector in a nuclear power plant.
In the SRNM measuring instrument in the nuclear power plant, a weak current from a fission chamber for an activation range input from a transmission cable is charged and amplified by a preamplifier circuit in a preamplifier and is transmitted by an SRNM signal transmission cable. Meanwhile, a core wire of the SRNM signal transmission cable connects with a signal output terminal in an SRNM processor and a core wire and a shield of a preamplifier power source supply cable connects with a direct current power source. Then, ferrite for removing common-mode noises is mounted on a terminal, or a part connecting with the preamplifier, of the preamplifier power source supply cable. Moreover, ferrite for removing in a normal mode is mounted near a power source supply point in a part of a core wire in the preamplifier.
COPYRIGHT: (C)2005,JPO&NCIPI
Setsuo Arita
Ken Nozaki
Tomoki Sakata
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