| Popis: |
We have constructed a capacitive transducer for the absolute measurement of the normal component of surface‐wave motion on a flat solid, the direction of travel of the wave being known. The transducer backplate is a cylinder and has cylindrical extensions on each end that act as electrostatic guards to render calculable the sensitivity and capacitance of the transducer. Compliant support elements are incorporated, resulting in negligible mechanical loading to the surface and flat frequency response over the range of 10 kHz to 1 MHz or better. The amplifier noise floor is equivalent to about 4×10−12 m rms with a 5‐MHz bandwidth. The upper limit to displacements measurable by this technique has not been established, but is large enough to encompass the range of interest. Estimated uncertainty of the sensitivity determination is less than 5%. |
