Patent GB-549658-A (GB)
Title: Improved apparatus for counting and measuring current impulses
IPC: H02H3/04
Filed: 1941-09-09
Abstract: 549,658. Current measurements. LANDIS & GYR SOC. ANON. Sept. 9, 1941, No. 11507. Convention date, Aug. 3, 1940. [Class 37] In a device for counting and measuring short current impulses, of the order 10<-6> to 10<-2> seconds duration electric impulse energy is transformed into a non-electrical form of energy and stored up, the stored energy then being used to an impulse counting element. The apparatus is particularly applicable for use with lightning arresters. In the apparatus shown in Fig. 1a, a part i L of the short current impulse i(t) to be measured is passed through a pair of closely coupled inductance coils L1, L2 and causes these coils to attract each other so that kinetic energy is stored in masses M1, M2 attached to the coils. The stored kinetic energy compresses an elastic intermediate member K and actuates a meter Z. Oscillation of the masses M1, M2 may be damped by air or liquid friction. A resistance R, of the type in which the current increases more rapidly than the terminal voltage, may be connected in parallel with the coils L1, L2 so that the proportion of the total current passing through these coils decreases with increase of the current. In another construction, Fig. 2, a part iH of the current impulse i(t) to be registered passes through a hot wire H in which the energy of the impulse is stored as thermal energy. The expansion of the wire H is registered by a meter Z. To prevent overloading the wire H with heavy impulses a resistance R may be employed as in Fig. 1a, or alternatively a spark gap F in series with a resistance S may be connected in parallel with the wire H. If minimal impulses are to be counted the resistance R may be replaced or supplemented by a condenser C, Fig. 1a, which stores up electric energy and transmits it to the transforming element L or H. The resistance R may be a part of the arrester. In a modification, Fig. 3, thermal energy stored in the element H ignites a small quantity of explosive in percussion caps P1 ... P6 which gives a signal or actuates a mechanical counter. A fresh percussion cap is then placed in position by spring pressure actuating a carrier spider, a meter Z for recording the number of 'impulses being mechanically connected to the spider. Instead of a heating resistance, the spark between points A1, A2 may be employed to ignite the explosive. Energy transformation may alternatively be effected by an electrochemical meter by which current impulse energy for instance of accumulators is transformed into chemical energy and then supplying the metering device, or by an electro-optical meter in which energy is accumulated by a luminous screen. The magnitude of the current impulses may be measured by arranging for the actuation of the counting drum of the meter to be dependent on the magnitude of the transformed impulse energy, as by the use of a fine ratchet wheel. A counting element may be used in addition to count the impulses. Fig. 5 shows an arrangement of three meters Z1, Z2 Z3, for counting impulses of widely differing magnitudes. Spark gaps F1, F2, Fn are arranged so that a small impulse heats the wire HI without causing any discharge at the spark gaps, these impulses being counted by the meter Z1. Impulses above a certain magnitude cause the spark gap F1 to break down, connecting the resistance R2 and wire H2 in parallel and causing registration on the meter Z2. Further increase of impulse current causes the spark gap F2 to break down and the meter Z3 to register. The spark gap Fn short-circuits the measuring device in the event of overload, a sheet of thin paper being perforated to register the overload. Instead of spark-gaps, gas-filled tubes may be used. In alternative arrangements several meters as shown in Figs. 1a or 2 of different degrees of sensitivity may be connected in series. Alternatively several counting devices with different degrees of sensitivity may be actuated by a single energytransforming element.