GB583794A - Improvements in arrangements for frequency measurement - Google Patents

Abstract

583,794. Frequency measurements. STANDARD TELEPHONES & CABLES, Ltd., and EARP, C. W. July 10, 1942, No. 9658. [Class 37] [Also in Group XXXVIII] In an arrangement of the kind described in Specification 581,201 in which a signal frequency lying between predetermined limits is measured by feeding it over parallel paths which introduce a differential delay depending on the frequency to the coils or windings of a phase-meter, the said coils or windings constitute an effective part of the delay network. In Fig. 2, the phase-meter is a dynamometer instrument having field windings F1, F2 arranged at right angles and a search coil S free to rotate in their field. The windings F1, F2 are tuned by condensers C1, C2 to the mid-frequency of the working range and are coupled by a condenser C4 so that the currents through them are always in quadrature, while the chain of tuned circuits forms a delay network which gives a variable phase relationship between the currents in S and those in F1 and F2. In Fig. 3 (not shown), additional tuned circuits are provided to increase the delay sufficiently to give a total phase rotation of 360 degrees over the working range. In Fig. 4 (not shown), the search coil S is connected at the end of the chain of tuned circuits. The arrangement may be employed with a meter of the kind described in Specification 537,743 which has no moving coil.