| 摘要 |
A system (10) accurately measures the resistivity of a material (12) via capacitive coupling without contact with the material (12). A transmission electrode (14a) sends signals through the material (12) to a reception electrode (14b). An oscillation mechanism (16) forwards a periodic signal at a predetermined frequency f to the electrode (14a), and a detection mechanism (18) receives a resistivity signal from the electrode (14b), which signal is proportional to the resistivity of the material (12), and translates the resistivity signal into a resistivity value for the material (12). The oscillation mechanism (16) comprises an oscillator (21) connected through a transformer (T1) to a quarter-wavelength stub (24), which feeds an excitation signal to the transmission electrode (14a). The detection mechanism (18) comprises a detector (31) connected via a transformer (T2) to a quarter-wavelength stub (26), which is directly connected to the reception electrode (14b). The detector demodulates the resistivity signal, which can then be displayed on a user interface, such as resistivity meter (32). The stubs (24, 26) prevent transfer of signals between the electrodes (14a, 14b) when no material (12) is present. Further, the system (10) is constructed so that it resonates at the predetermined frequency f.
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