A direct digitizing seismograph

摘要: abstract A seismograph is described in which capacitance transducers on either side of the inertial reactor determine frequencies two Clapp oscillators. The oscillators are heterodyned and resulting frequency, varying between 10 kc 100 kc, detected by a frequency or period counter an analog output. latter drives self-balancing potentiometer through cathode follower adjustable twin-T filter. It also circuit with very long time constant keeps boom centered coil magnet transducer. electronic noise corresponds to displacement less than 1.25 m μ . sensitivity about 400 cps per micron. dynamic range db at resolution. digital output temporarily form printed punched tape. special magnetic tape recorder being built.