Patent GB-695240-A (GB)
Title: Improvements in testing apparatus for electric circuits and components
Inventor: MILLS ROBERT VICTOR
IPC: G01R31/02
Filed: 1951-05-28
Abstract: 695,240. Detecting and locating faults. BRITISH THOMSON-HOUSTON CO., Ltd March 13, 1952 [May 28, 1951], No. 12460/51. Class 37. An equipment for testing component apparatus used in the operation of lowpressure electric discharge lamps comprises input terminals to which a source of A.C. is adapted to be connected, and sets of output terminals to which arc respectively connectible the following components: (a) a low-pressure electric discharge lamp, (b) a thermal or glow starter switch, and (c) an inductance, circuit arrangements and switches being provided for selectively connecting the input terminals to any one of the sets of output terminals through test circuits. A source of A.C. is connected to input terminals P1, the components under test being connected to output terminals P2 . . . P6. Multi-bank selector switches 1S, 2S, 3S, 5S, 6S and a single-bank selector switch 4S, together with resistors R1 . . . R14 and inductances L1 ... L4 enable circuits to be connected for testing the different components. The input voltage applied to the input terminals P1 is supplied to an auto-transformer T which has tappings 37, 16 enabling a standard output voltage, as measured by a volt-meter V, to be obtained at output terminals 14, 15. To test a low-pressure fluorescent lamp, its caps are connected to output terminals P2, P3 and the switches are set so that one of the inductances L1 ... L4, according to the wattage of the lamp, is connected in series with the lamp and a push-button switch 22 between the transformer output terminals 14, 15. On closing the switch 22 a circuit is completed through the output terminals P2, P3 so that the electrodes of the lamp are heated. The switch 22 is then opened and the lamp should strike, indicating its sound condition. For testing the continuity of the electrodes of the lamp, the switches are set to complete a test circuit between secondary tappings 26, 15 on the transformer T, between which there is a voltage of about 6 volts, an indicator lamp 29, and the terminals P2, P3, the lamp 29 lighting if the lamp electrodes are continuous. A thermal starter switch to be tested is connected to output terminals P4, which include contacts B to be connected to the heater and contacts C to be connected to the switch contacts. The switches are set to close a circuit from the tappings 14, 15 through one of the inductances L1 . . . L4, one of the resistors R12 ... R14, and the contacts B, C. If the heater of the thermal switch is sound it heats up and opens the contacts. The indicating lamp 29 is connected across the selected resistor R12 ... R14 so that the voltage drop across the resistor causes the lamp 29 to light. Opening and closing of the starter switch causes flashing of the lamp 29. The push-button switch 22 is then closed and connects one of the resistors R9 ... R11 in parallel with the starter contacts and the selected resistor R12 ... R14 in series. When the starter contacts are open, a current continues to flow through the starter heater of the same value as the minimum required for holding open the starter switch. The indicator lamp 29 then remains de-energized if the characteristics of the starter switch are correct. For testing a glow starter it is plugged into the socket P4, the bimetal contacts being thereby connected between the terminals C. The terminals B are short-circuited by the internal connection of the starter. Glow discharge between the starter contacts causes them to close and complete a circuit through one of the inductances L1 ... L3 and one of the resistors R12 . . . R14 and the indicator lamp 29 lights. When the starter contacts cool and open the indicator lamp is de-energized, so that it flashes on and off, indicating that the starter is operating. The push-button 22 is depressed and connects one of the resistors R9-R11 in parallel with the starter contacts. The indicator lamp 29 remains de-energized if the starter complies with the Specification. To test a lamp choke it is connected to the output terminals P5 and the switches are set so that the choke to be tested is connected to the secondary winding of the transformer T through one selected resistor R 1 . . . R4 shunted by a selected one of the resistors R5 ... R8 and the voltmeter V. The voltmeter indicates the voltage developed by the test current flowing through the choke to be tested and the selected one of resistors R1 ... R4 to indicate that the current through the choke is correct and its impedance is accurate. The same circuit may be used for testing the insulation between the outer case and winding of the choke at mains voltage, and for checking the continuity and insulation of capacitors. For testing the continuity of circuits a low voltage (e.g. 6 volts) winding 43 is connected to a pair of output terminals P6, to which may be connected a pair of probes, one of which includes an indicating lamp which lights if the circuit is continuous.