PURPOSE: To reduce noise by forming a liquid transfer needle as a part of a coaxial electrode arrangement, thus providing no potential difference between a signal electrode and a compensation electrode.
CONSTITUTION: An output 23b of a separate amplifier circuit 23 is connected with a first coaxial electrode 12 by way of a conductor 20b of a coaxial cable 20. The output signal of the circuit 23 has its level and phase balanced with the input signal, so that there is no potential difference between a compensation electrode 12 and a needle 5 and the capacitance existing between the cable 20 and a coaxial electrode arrangement 11 has no effect. Due to this active compensation, the capacitance of the arrangement 11 including the cable 20 is mainly formed by a stray electric field between an extremity 5a of the needle 5 and an electrode 13. This stray electric field workds as a useful capacitance and forms a potential divider together with a resistance 19. Corresponding to the increase of the capacitance, the capacitive reactance of the useful capacitance is reduced so that a potential difference is produced at the input 23a of the circuit 23 and is measured as the useful signal.
| JP2001183217 | ELECTRODE FOR CAPACITANCE TYPE LEVEL GAUGE |
| JPS59621 | LEVEL SWITCH |
REONHARUTSU GAITSUSURAA
ANDOREA JIIGURU
Next Patent: METHOD AND INSTRUMENT FOR MEASURING BOUNDARY LEVEL OF SEDIMENT