| 摘要 |
A self inverting gauging system for such parameters as capacitively sensed distance or inductively sensed resistivity in which the sensor provides an output inversely varying with the dimension of interest. The gauge typically includes a dual slope integrator responsive to a reference value on the up integration and to the sensor output on the down integration. The interval of the down integration necessary to reset the integrator to the original value varies directly, rather than inversely, with the dimension of interest and is typically provided as the digital output indication of a counter. In the application to resistivity gauging, the up integration reference signal is preferably provided by the output of a thickness gauge such that the ultimate counter display represents element resistivity compensated for thickness. To provide automatic error compensation two integrator loops are provided, one selectively closed around the dual slope integrator alone to provide a compensating reference for its errors, and the second, subsequently activated, to close an integration feedback loop around both the transducer and the dual slope integrator in order to provide a reference signal compensating for the errors of the entire system.
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