GB619635A - Improvements in or relating to apparatus for testing ignition systems for internal combustion engines - Google Patents

Abstract

619,635. Testing ignition. ENGLISH ELECTRIC CO., Ltd., and HEYES, J. B. Dec. 18, 1946, No. 37263. [Class 7 (iv)] In apparatus for testing the ignition systems of internal-combustion engines in which signals obtained from the low-tension circuits of the ignition systems are displayed on a cathode-ray oscillograph, impulses for synchronizing a time base of the oscillograph with the engine firing cycle are taken to the apparatus through a condenser and a transformer, which does not pass the higher frequency components of the impulse, so that attenuation, which would otherwise occur when long leads are employed, is reduced. A split brass sleeve 8, Fig. 1, is passed round the lead to one of the sparking plugs 1 ... 6 and all six sparking plug leads are enclosed in a "screen" 7. A "screened" connection 9 from the brass sleeve 8 is led to one side of an earthed primary winding of a transformer 10. The earthed secondary winding of the transformer 10 is connected to the primary of a trigger circuit transformer 12 as described in Specification 563,502. In an equivalent circuit, Fig. 4, a condenser 13, which is representative of the capacity between the brass sleeve 8, Fig. 1, and the sparking plug lead, is in series with a condenser 14 which is the capacity comprised between the brass sleeve 8 and "screen" in addition to the capacity of the "screened connection 9, Fig. 1. A potential divider is formed by connecting the primary winding of the transformer 10, Fig. 1, in parallel with the condenser 14. Condensers 17, 18, Fig. 4, respectively represent the capacity of the primary winding and the connection from the secondary to the trigger circuit transformer 12, Fig. 1, the latter capacity including the secondary winding of the transformer 10.