| 摘要 |
<p>The impedance is measured by connecting it in series with a generator and reference impedance in an operational amplifier circuit. This allows a precise measurement to be made at high frequencies and is particularly useful for measuring inductance of metal detection probes. An operational amplifier (1a) supplies a high frequency signal for a reference impedance (5a) which is similar to the impedance of a detector probe winding (7a). The signal is inverted via an adjustable gain amplifier (8) for a second amplifier (16) and reference impedance (5b) circuit. The amplifier outputs (4a,4b) are connected to another amplifier (9) whose output represents the difference in impedance values of the two halves of the detector coil assembly. The impedance of a half winding is given via a variable gain amplifier (10).</p> |
