GB502711A - Improvements in or relating to automatic electrical apparatus for indicating, measuring and/or giving warning of temperature changes - Google Patents

Abstract

502,711. Electric signalling systems. ELLIOTT BROS. (LONDON), Ltd., SILCOCK & SONS, Ltd., R., FREELAND, F. L., and BROADHEAD, F. G. Nov. 25, 1937, No. 32461. [Class 40 (i)] In a system for indicating, recording and/or giving warning of temperature changes at a number of points, e.g. ships' holds, silos, &c., the points are provided with resistance thermometers (not shown) which are connected to pairs of termimals a<1>, d<1> .... a<50>, d<50> and together with corresponding fixed resistances f<1> ... f<50> form Wheatstone bridge connections with common resistances h, h<1>, h<2>. An indicating or recording instrument (not shown) of the crossed coil type is connected to terminals k ... k<3>, the terminals k<2>, k<3> of one coil being connected across the supply c and the terminals k, k<1> of the other coil to the junction of the resistances h, h<1>, h<2> and the common contact m of a distributer switch having contacts connected respectively to the junctions between the thermometers and the resistances fl ... f<5>. The distributer is driven stepwise through gearing q by a motor p and the arrangement is such that variations of temperature measured by the thermometers are indicated by the common indicator. Records may be taken on a chart by depressing the instrument pointer by a chopper bar periodically operated by an electromagnet connected in the circuit v and operated by the cam-operated contact t. Temperatures outside a predetermined range may be indicated by the operation of one or other of a pair of contacts by the instrument pointer, the contacts being adjustable to determine the limits of the range. The contacts are connected to terminals w and operated by an electromagnet x to stop the motor B and operate an alarm B. Cam-operated contacts l are included in the instrument circuit so as to close the circuit only when the switch arm o engages a distributer contact. A relay C, connected in shunt with the motor, controls green and red indicator lamps G, R. The selector switch may also carry an indicator dial which when the motor is stopped indicates the number of the affected circuit. The condition of a thermometer may be tested for faults by a switch D which when operated short-circuits the resistance h<1> to disturb the balance of the circuit and cause the indicating instrument to provide an indication as to the sound or faulty condition of the thermometer. The distributer may be manually operated by a handle E. The system also is such that alarm indications are given in the event of failure of the supply sources c, u.