The SSQ-1 Digital Tape Recording Horizontal Pendulum Tiltmeter is an instrument of high sensitivity to detect the changes of ground tilt. It uses a quartz horizontal pendulum held by Zollner bifilar suspension to sense vertical displacement, the eddy-current transducer on the pendulum converts its displacements into electric signals. Then a microcomputer is used for data acquisition and printing as well as digit tape recording. And at the same time, a filtering pen recorder is used for visible recording. The scale value of the instrument is calibrated by computer using the known tilt angle of the bulging plate — mercury cup. The scale value is 0.3–0.5 m(″)/mV.