Thorn Emi Instruments Limited

David C Tedd

Christopher L Steggall

Peter G Nichols

Terence M Friend

Kenneth Gatland

Hugh R Marsh

David M Kennedy

Stephen J Masters

John B Williams

Electrical measuring instrument

A multimeter is provided with two slide switches, one switch providing a selection of four functions, i.e. 'OFF', 'AC', 'DC/JUNCTION' and 'RESISTANCE/CONTINUITY' and the other switch providing a selection of six range settings and a 'JUNCTION/CONTINUITY' setting. The multimeter also has three input sockets for insertion of test leads. At least two of the combinations of the switches and sockets are incompatible, i.e. 'AC' and 'JUNCTION/CONTINUITY', and a current input socket and 'RESISTANCE/CONTINUITY'. An internal buzzer is incorporated in the multimeter to provide an audible indication to a user that an incompatible combination has been selected. The buzzer is preferably also used in junction and continuity test modes.

Multimeters

An instrument for measuring electrical resistance or reactance comprises a sine wave generator which generates an a.c. signal and reference signals for a phase sensitive detector. The a.c. signal is applied to a decade attenuator which adjusts its amplitude in dependence on a range switching. The signal is passed to a bridge section, wherein it is applied to a component to measure the value thereof. A voltage output, indicative of the value, is fed to a gain block, wherein its amplitude is re-adjusted in dependence on an input from the range switching. The voltage output is operated on by a phase sensitive detector and passes to a digital display. In the reactance mode, set by a function switching, the a.c. signal is phase shifted before being applied to the component, so that the voltage output is in phase with the reference signals.

Instrument for measuring electrical resistance or reactance

Carrying case for electrical measuring instruments or the like

A switch actuator mechanism including a slider which can execute movement in steps along a linear track, the step-wise movement being governed by the interaction of a pair of cam-followers, carried by the slider, with respective cam-surfaces disposed alongside the track, one to either side thereof. The cam-followers are resiliently urged into contact with their respective cam surfaces and permit the slider to assume, alternately, stable and unstable conditions at locations disposed in series along the track. Beyond one of the extreme positions at which the stable condition is assumed, the cam surfaces are formed with respective inwardly inclined, linear surface portions along which the respective cam-followers can run while being urged against the resilient force, thereby permitting the slider to travel beyond the extreme stable position to enable a switch means to be actuated by the slider, or some attachment thereto, the slider being restored to the aforesaid extreme stable position, after such actuation, by the resilient force applied to the cam-followers.

Switch actuator mechanism

Growing community of inventors

Folkestone, United Kingdom

David C Tedd