đã có thể để giữ được kiểm soát bởi sử dụng cortisone. Tuy nhiên, ông tiếp tục cống hiến năng lượng của mình để mở rộng địa chất từ một doanh nghiệp nghiêm chỉnh trên mặt đất bao phủ lập bản đồ địa chất của mặt trăng,sơ bộ của các mẫu đã đồng ý rằng, | 292 INSTRUMENTS FOR LABORATORY AND FIELD MEASUREMENTS CHAP. 9 Figure 9-18. Connectors used for instrumentation. The MS- and microphone-type connectors are used with two-conductor cables with the shield connected to the body of the connector. Both connectors come in various numbers of cable contacts but the MS type has the greatest selection. The microphone-type connector has the distinct advantage of being easier to connect and disconnect. When the MS-type connector is used to connect two cables it is almost impossible for the inexperienced person to decide what part to unscrew to disconnect the cables. This often causes the wires to be broken off inside the connector. With the microphone connector this problem does not exist. The banana-plug connector can be used where shielding is not important. Its low cost and ease of assembly make it a popular connector where large-level signals are involved. Vibration Measurements for Field Tests In general there are two testing methods for measuring dynamic soil properties in the field. One method uses a source of steady-state vibration and the other method uses a single impact as a source of vibration. Theories given in Chap. 4 provide the basis for interpreting the measurements from these two tests. The steady-state-vibration test is used for determining the velocity of Rayleigh waves from which the shear modulus of the soil can be calculated. The impact test provides information on the velocity of the P-wave. Both methods provide information on the variation of soil properties with depth and can be used to determine the location of boundaries between layers. Field methods and instrumentation used in performing these tests will be considered in this section. After an installation is completed it is desirable to make measurements to compare the performance of the design facility with that predicted by SEC. VIBRATION MEASUREMENTS FOR FIELD TESTS 293 design. Measurements are also required for analyzing vibrations of .
