Patent GB-1298350-A (GB)
Title: Automatic testing apparatus for a multiconductor electric cable
IPC: G01R31/58
Filed: 1969-12-30
Abstract: 1298350 Cable testing STANLEY DENKI KK (STANLEY ELECTRIC Co Ltd) 30 Dec 1969 [13 May 1969] 63222/69 Heading G1U The continuity of conductors in a multiconductor cable whose ends are respectively connected to two connectors is tested automatically by an apparatus incorporating two connection adapters for respective connection to the connectors, one adapter having the same number of terminals as there are cable conductors, connected in pairs, the other having the same number of terminals as cable conductors, some terminals being connected in pairs, the rest being equal in number to twice a desired number of groups. The adapters are such that the cable conductors are divided into the desired number of groups, the conductors in each group being series connected between pairs of the rest of the terminals. The apparatus further includes a number of switching units operable in sequence and each respectively connectible with a group of series connected conductors via the second adapter, and assuming an ON state when a corresponding group forms a complete series connection. A control device coupled with a first switching unit enables a test sequence to be initiated, by connecting a supply in series with the first switching unit. Each switching unit has a self holding arrangement coupled with it. Second control devices are each operated by a corresponding switching unit in its ON state to connect the supply in series with the next unit in sequence. Each unit in its ON state releases the ON state of the preceding unit. The test results are indicated by a display arrangement operated by the switching units. To test a cable 20 Fig. 2 incorporating twelve conductors and having connectors 21, 23, adaptors 22, 24 inter-connect the conductors into three groups each of four series connected conductors. The adaptor 24 provides terminals enabling the groups to be connected to appropriate terminal pairs 34, 35, 36 &c., of a test circuit Fig.3. Voltage is applied to a first switching unit in this circuit by operating switch 32. This establishes a current path through relay A, contacts 30-1a, 30-0a of switch 30, the conductor group 1a, 1b if properly in order, contacts m 4 , i 4 .... a 4  and contacts 30-1s, 30-0s. The operation of relay A illuminates lamp 40 by closing a 2 , brings in self holding contact a 1 , and changes over a 4  to enable a similar path through relay B to be completed if the respective conductor group is in order. If this is in order, lamp 49 is illuminated, the circuit path for relay C established and contact b 3  opened, causing relay A to fall out after a time set by capacitor 43. If all conductor groups are in order, the lamps 40, 46, 49 &c., are illuminated and extinguished in cyclic order. If a fault occurs the sequence is interrupted and the type and location of the fault may be deduced from the pattern of lights which are illuminated or flash. Insulation resistance between sets of connected conductors may be tested by use of the circuit incorporating transistors 81, 82. With the switch 30 set to position 2, and potentiometer 70 set to the same value as reference resistor 69, this circuit is adjusted by altering resistor 71 until relay N is just actuated. The switch is then set to position 3 wherein half the groups of conductors are connected together and the other half are connected together and to resistor 70. The relay M is activated to open contacts m 5  and resistor 70 then adjusted until relay N operates again. The amount of adjustment corresponds to the insulation resistance.  In a further arrangement Fig.4 (not shown) a more complex switching system is provided so that relay A is operated in precisely the same way as all others, to avoid erroneous indication of particular types of fault associated with the conductor group associated with that relay. An alternative insulation resistance measuring circuit is also provided, in which the battery supply is used to activate an oscillator whose output is transformer amplified, rectified and applied to appropriate leads via a meter, adjustment being made by a resistor to bring the meter to a standard reading.