| 摘要 |
In order to ascertain the magnitude Ri of an unknown resistance element in digital terms, two calibrating resistances of known magnitudes R1 and R2=mR1 (with m>1) are connected in circuit with a capacitor, to form a switchable RC network, during two gating periods whereas the unknown resistance element is inserted in their place during a third gating period. A multiplicity of counting pulses are fed during each gating period to a pulse counter delivering their count to an arithmetic unit which determines the ratio Ri/R1 from the several pulse counts and from the factor m. The switchable RC network may be part of a one-shot pulse generator, establishing a variable gating period for counting pulses of a fixed cadence, or of an astable multivibrator generating different counting pulse rates during gating periods of constant duration. The fixed pulse cadence or the constant gating periods are established by another RC network which may share a common coincidence (AND, NAND or NOR) gate with the switchable network.
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