MEASURING METHOD OF QUANTITY OF MERCURY ENCLOSED IN FLUORESCENT LAMP

PURPOSE:To measure the quantity of mercury simply and surely by a method wherein a fluorescent lamp heated above a prescribed temperature is lighted by a resonant ballast having a secondary no-load voltage waveform formed of superimposed resonant waves, and a lamp-voltage waveform obtained on the occasion is measured. CONSTITUTION:In a temperature controlled bath 2, a fluorescent lamp 1 is lighted with an input voltage fixed at 95V. On the occasion, switches 5 and 6 are opened. In these conditions, the temperature in the temperature controlled bath 2 is raised gradually, and the amplitude A of the bottom portion 11 of a restrike voltage 10 in a lamp-voltage waveform 9 of the figure is measured by an oscilloscope 4. Then the result shown in the figure, namely a graph of an ambient temperature ( deg.C) to a value of the amplitude A, is obtained. From this graph a value at which the value of A turns saturated notwith standing a rise in the ambient temperature is read. In this case, the value of A is 42. Then, the quantity of mercury enclosed in said lamp is read to be 20mg from a graph of relationship between the A value and the quantity (mg) of the enclosed mercury, which is shown by the figure prepared separately.