A seismometer acquisition has been used in Changping observing station to gather the output of strainmeter. The original sampling rate of the strainmeter is 1 time per minute, it's 100 Hz for seismometer acquisition. Plenty of higher frequency data are recorded and the minutely data calculated from seismometer acquisition are consistency with that of the original data sampled by strain acquisition. Spectrum of the strain waves are compared with seismic wave recorded by a seismometer in Shisanling seismic station, their trend are almost the same, but some lower frequency ingredients existed in strain waves.
Most precursor instruments are digitalized in our country in this years, their sampling rate is 1 time per minute. Signals such as daily, monthly, yearly or longer periodic information are hided in the observational data. Under normal circumstances, these information are enough to researcher for the earthquake situation analysis. However, the sampling rate of seismometer is higher a lot, it is 100 times per second. In fact, higher frequency strain waves are recorded by bore hole strainmeter in simulated records. In few years, high frequency sampling data has been tried in some earthquake observing station along with the fast development of the observing techniques. One Hz sampling data with the water level measurement was recorded in Fujian, integrated water level oscillation was recorded. A test which observe water level oscillation with EDAS-3 acquisition unitwas devoloped by Shu youliang in Zhouzhi station, Shannxi province. In the application of high frequency sampling data, Zhang Ziguang compared the strain value induced by seismic surface wave and the change of water level in Tangshan mining well. Many precursor instruments, such as bore hole strainmeters and underground fluid measurement units, are used in Changping Earthquake Observing Station (short title CP Station).