TESTING APPARATUS

Abstract: Apparatus for testing the ballast (34) of a fluorescent lamp fitting by replacing the lamp or a starter for the lamp with a unit (10, 30) which substitutes a load impedance (15, 38) for the lamp. Indicators (13, 14, 15, 37) respond to current in the load impedance to show satisfactory or defective condition of the ballast.

Description: TESTING APPARATUS TECHNICAL FIELD This invention relates to apparatus and methods for testing an inductive load such as a fluorescent light choke ballast circuit, and, in some embodiments, the circuitry of light fittings incorporating such loads. BACKGROUND ART Problems are encountered in the use of fluorescent tubes where the inductive ballast circuit develops a fault and a higher current and/or voltage is applied to the fluorescent tube than required, which may lead to shortened tube life or even tube damage. Provided that the ballast is operated within its recommended temperature range, it should enjoy a life of at least 10 years in continuous use and replacement of the ballast is recommended at this time. However, it is not always a simple matter to establish the age and condition of an existing ballast circuit for a fluorescent tube. DISCLOSURE OF THE INVENTION The object of the present invention is to provide a method and apparatus for testing a fluorescent lamp ballast circuit in a simple and effective manner, which enables the testing to be carried out at the time of lamp replacement, avoiding the cost of damaging new lamps by placing them in fittings having defective ballasts. The invention may be embodied in ways which additionally enable the testing of other components of the fitting. There is provided according to the present invention a testing device for low-pressure discharge light fittings comprising means capable of engagement with the fitting to provide a load substantially equivalent to a lamp thereof, and means responsive to the circuit parameters of the fitting to indicate a fault condition thereof. In one form of the invention, the testing device is particularly employed for ballast testing, and comprises means capable of engagement with the fitting in place of the lamp. In another form of the invention, the device is connected to the fitting by removal of the starter, the device plugging into the starter socket. In this form of the invention, the tube or tubes are removed and replaced by devices which short circuit the tube contacts. The invention may include solid state circuitry including a pair of light emitting diodes (LED) connected via voltage amplifiers for monitoring the voltage drop across the .load. One LED signifies a normal voltage/current condition and the other LED signifies an abnormal voltage/current condition. The invention also includes a method of testing a light fitting for a low pressure discharge tube comprising the steps of inserting a test load equivalent to said tube and comparing the voltage drop across the load or the current flow therein with the voltage or current values of normal tube operation. BRIEF DESCRIPTION OF THE DRAWINGS The invention will be described in greater detail having reference to the accompanying circuit diagrams in which : * Fig. 1 shows in side elevation a first embodiment of the invention; Fig. 2 shows a schematic circuit diagram of the embodiment of Fig. 1; Fig. 3 shows a modified form of the embodiment of Fig. 1; Fig. 4 shows schematically, a second embodiment of the invention; and. Fig. 5 is a schematic circuit diagram of the embodiment of Fig. 4. DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION The device of Fig. 1 is constructed in the form of a tube 10 having dimensions corresponding to those of the tube intended for the light fitting to be tested, and the testing device is provided with end contacts 11 in the same dimensions and configuration as those of a standard fluorescent tube of the appropriate length or power consumption. Mounted on the outside of the tube so as to be conveniently operable upon engagement of the tubular device with the fitting to be tested, are a pair of test buttons 12, and a pair of light-emitting diodes 13 and 14, respectively green and red. The purpose of the two test 5 buttons 12 is to ensure that the unit is isolated from mains power during insertion into and removal from the light fitting, by requiring the use of both hands to energise the unit. Fig. 2 shows a circuit arrangement suitable for use 10 in the unit shown in Fig. 1. The behaviour of this circuit is such that a faulty ballast 34 will cause the red LED 14 to light as well as or instead of the green LED 13. If the green LED 13 alone lights, it indicates that the control circuit for the tube is in good operating 15 condition. The test apparatus may therefore be engaged with the light fitting in the same manner as a fluorescent tube, and when the device is connected to the fitting circuitry by means of the two test buttons 12, a load resistance 15 * 20 is placed in series with the ballast. This load resistance is set to correspond with the impedance of a correctly functioning fluorescent tube of the correct type for the fitting in question. The voltage drop across 15 is rectified by diodes 16 25 and 17 and smoothed somewhat by capacitor 18. Across 18 there is another resistive load 19 and a variable resistance 20. The voltage across 20 is applied to the Zener diodes 21 and 22. 22 is set to conduction from 20 which is set to provide triggering with a good working 3-0 ballast and this conduction triggers transistor 23. When 23 is in a conducting state the green LED 13 is turned on. If the ballast is faulty, due for example to some part or parts of its winding being short-circuited, the resulting larger than normal voltage drop across 15 will 35 result in a larger than normal voltage applied to Zener diodes 21 and 22. As a result 21 will avalanch and a voltage is applied to a . Darlington pair 24 and 25 causing the red LED 14 to light. Thus, where the green LED 13 only operates, the ballast is in good condition. When the red LED 14 or both red and green LED's light, the ballast is faulty. Thus, the method and apparatus of the invention operate to duplicate the normal load as seen by the choke ballast and to monitor the resultant current flow or voltage. An audible alarm device such as a transducer 26 may be incorporated into the test equipment such that if a fault is detected a signal sounds. As indicated above, in the preferred form of the present invention, the measuring circuitry, actuating test buttons and indicator devices are carried by a housing which is dimensioned to correspond with a fluorescent tube of the dissipation for which the light fitting to be tested is designed. As is well known, fluorescent light fittings are designed for fluorescent tubes of standard lengths in ratings of 18/20 watt, 30 watt, 36/40 watt and 58/65 watt. In a particularly advantageous embodiment of the present invention illustrated in Fig. 3, a basic testing unit 10a of 2 ft. in length for use with 18/20 watt fittings, may be provided with extender units 10b which, in a modular fashion, engage with the basic unit to extend its length to one of the 3, 4 or 5 ft. lengths of the other standard fluorescent tubes. Each of these add-on units incorporates additional load resistance, so that the load presented to the light fitting under test, always corresponds substantially with that presented by the correct fluorescent lighting tube. The units 10a and lob are interconnected by suitable plug and socket fittings 11a. In another version of this embodiment of the invention suitable for use with fittings of different power consumption, the unit 10 may be telescopic, so that its length can be adjusted to suit the fitting under test, the load resistance being automatically adjusted upon telescoping movement of the housing sections. Fig. 4 shows in a schematic fashion the basic principle of the second embodiment of the invention to be described herein. In this case, the testing circuitry is enclosed within a housing 30 which is preferably of the same size and cylindrical shape as a standard- fluorescent lamp starter, although this housing may be larger than the starter if this is allowed by the configuration and dimensions of the fitting to be tested. The device is provided with a pair of pins 31 of the same size, shape and spacing of those of the standard starter, so that the device may be plugged into the starter socket or sockets of the fitting to be tested, upon removal of the existing starter or starters. The apparatus of this embodiment further comprises a pair of end plugs 32, which are dimensioned to correspond with the ends of a fluorescent tube, and are provided with pins 33 conforming to the dimensions and spacing of a standard fluorescent tube. The pins 33 are internally connected, so that the removal of a tube and its replacement by a pair of end plugs will place the ballast 34 of the fitting directly in series with the pins 31 of the testing device. A typical circuit which may be employed in the testing device of this embodiment, is shown in Fig. 3, where the starter socket connections are shown at 35. As before, the device incorporates a push button here shown at 36, and an LED indicator 37. Current flowing in the load resistors 38 upon depression of the push button 36 is transferred by a current transformer 39 to a testing circuit comprising a rectifier and smoothing circuit 40, and an integrated circuit 41 which drives the LED indicator, which glows if the ballast or the internal wiring of the fitting is faulty. Preferably, the integrated circuit 41 produces a pulsed output to the LED, the pulse rate of which increases with increasing voltage input to the integrated circuit, so the worse the condition of the ballast 39, the higher the rate of pulsing of the LED indicator. Preferably the indicator will be driven to a continuous output if no current flow is detected, indicating an open circuit in the fitting. It will be appreciated that many approaches may be taken to the electronic design of equipment according to the invention. For example, instead of the use of a push button for temporary insertion of the load resistors into the circuit, a sample and hold circuit may be incorporated in which current flow through the load resistors is automatically applied at intervals and the result of the current measurement stored. Other approaches to the measurement of the performance of the ballast and of the fitting circuitry, under the simulated operating conditions in question, may also be adopted within the scope of the present invention.

Claims: CLAIMS : 1. Testing apparatus for low-pressure discharge light fittings, comprising means capable of engagement with the fitting to provide a load substantially equivalent to a lamp thereof, and means responsive to the circuit parameters of the fitting to indicate a fault condition thereof. 2. Apparatus according to claim 1 comprising a housing dimensioned to fit into said fitting in place of said lamp, said housing being provided with electrical connectors substituting for those of said lamp, to place said apparatus in the circuit of said fitting. 3. Apparatus according to claim 2 further comprising a load impedance substantially corresponding to the impedance presented by a correctly operating lamp in said fitting. 4. Apparatus according to claim 3 further comprising means responsive to current flow in said impedance when said fitting is energised, and indicator means responsive to the detection of normal or abnormal current flow, to provide an indication of satisfactory or unsatisfactory condition of said fitting. 5. Apparatus according to claim 4 wherein said indicator means comprise first indicator means responsive to the detection of normal current flow to provide an indication of satisfactory condition, and second indicator means responsive to abnormal current flow or the absence of current in said impedance, to indicator a fault condition of said fitting. 6. Apparatus according to claim 4 further comprising two manually operated switch means connected in series with said impedance and located on said housing in such a way as to require two hands for operation of both said switch means. 7. Apparatus according to claim 5 wherein said first and second indicator means each comprise a visible indicator device. 8. Apparatus according to claim 1 for testing fittings of the kind comprising a removable starter device engaged in a starter socket provided on said fitting, wherein the device comprises a housing and electrical contacts engageable with said starter socket in place of said starter device. 9. Apparatus according to claim 8 further comprising means engageable with the " lamp sockets of said fitting to short-circuit the contacts thereof. 10. Apparatus according to claim 9 wherein said means responsive to circuit parameters comprises means responsive to current flow in said fitting when said fitting is energised and means responsive thereto to indicate normal or fault condition of said fitting. 11. A method of testing a light fitting for a low pressure discharge lamp comprising the steps of inserting a test load equivalent to said lamp and comparing the voltage drop across said load or the current flow therein with the voltage or current values of normal lamp operation.

Inventors: BAKER EDWARD JOSEPH, BAKER ROBERT HAMILTON, PRIEM ERROL FRANKLIN, BAKER, EDWARD, JOSEPH, BAKER, ROBERT, HAMILTON, PRIEM, ERROL, FRANKLIN
Applicants: BAKER EDWARD JOSEPH, BAKER ROBERT HAMILTON, PRIEM ERROL FRANKLIN, BAKER, EDWARD, JOSEPH, BAKER, ROBERT, HAMILTON, PRIEM, ERROL, FRANKLIN
Application year: 1986
Main classification: G01R31
IPC codes: G01R31, H05B41