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Life testing of incandescent lamps at the bureau of standards
NOTES
FROM
THE
U. S. B U R E A U
OF STANDARDS.*
R E P O R T OF T H E T E N T H A N N U A L C O N F E R E N C E W E I G H T S A N D M E A S U R E S , MAY 25-28, I915.
ON
THE report is a record of the proceedings of the Conference, which is composed of state and local weights and measures officials from various parts, of the United States. It contains, among other matters, short reports of the condition of weights and measures work in about twenty-five states; and technical papers dealing with the testing of electric meters, railroad track scale tests made by the Bureau of Standards, a method of adjusting railroad track scales, a discussion of automatic scales, system of keeping records, and weights and measures work from the standpoint of an efficiency engineer. The Conference adopted at this meeting extensive and comprehensive tolerances and specifications for weights and measures and weighing and measuring devices, which are given in the appendix of the report, together with a model state law on weights and measures, previously adopted. L I F E T E S T I N G OF I N C A N D E S C E N T LAMPS AT T H E B U R E A U OF S T A N D A R D S . t By G. W. Middlekauff, B. Mulligan, and J. F. Skogland.
[ABSTR*CT.] SINCE the year 19o8 the Bureau of Standards has inspected and tested the incandescent electric lamps which have been used in all departments of the government, amounting at present to about 1,25o,ooo lamps annually. The specifications under which these lamps are purchased are published by the Bureau as Circular ~3 and are recognized as standard by the manufacturers as well as by the government. They are used also by many other purchasers of lamps. Application of these specifications necessitates careful inspection and reliable life tests. The lamps are first inspected at the factory by Bureau inspectors, five per cent. taken at random from * Communicated by the Director. t Scientific Paper No. 265. 697
698
U.S.
BUREAU (IF STANDARDS NOTES.
[J.F.I.
each package being examined. These nmst conform to certain specified requirements as regards bulbs, bases, filaments, vacuum, etc. Lamps which pass these requirements are then run on the photometer to determine their candle-power and the watts consumed, and if the required percentage of the lamps falls within the specified limits the lamp nearest the mean value of each group of not more than 25o lamps is selected, labelled, and sent to the Bureau to represent the group on life test. Upon their receipt at the Bureau these samples, which a:t present amount to about 5ooo annually, are measured for voltage corresponding to the efficiency at which it is desired to run them on life test. A life test is said to be normal when it is run at the efficiency required by the specifications, and forced when it is run at a higher efficiency. Carbon lamps are usuallv tested at normal, while tungsten lamps, on account of their long life at normal, are forced in order to complete the test without unreasonably delaying the delivery of the lamps they represent, which must be held by the manufacturers pending the results of the test. The life is specified as the number of hours a lamp at rated efficiency will burn un,til its candle-power has become reduced to 8o per cent. of its original value. In the case of forced tests the actual life must be corrected by the proper factors to correspond to normal (rated) efficiency. In order to facilitate the photometric measurements of the life-test lamps and still secure a permanent, accurate, and, as nearly as possible, automatic card record of each lamp tested, certain modifications and additions have been made to the photometer used in this work. These include a watts-per-candle computer and a recording device by which observed values of candle-power, watts, watts per candle, and actual life are recorded on a separate card for each lamp. These records are made in such a way that life at forced efficiency may be corrected to life at normal without computation or reference to tables of factors. The test lamps, having been rated as described above, are then ready for the life racks, where they are burned at the respective voltages found until their candle-power has dropped 2o per cent. In order to obtain reliable results the voltage must be accurately adjusted and carefully regulated during the test. The Bureau's life-test electrical equipment is so designed that by a system of auto-transformation any voltage from 78 to _.06omav be obtained
May, i916. ]
U.S.
BUREAU OF STANDARDS NOTES.
699
and the exact value approximated to within one-tenth of one per cent. By a Tirrill regulator this voltage is kept within the specified limits of plus or minus a quarter of one per cent. Another important element in a life test is the elapsed time of burning. This is accurately determined bv means of an electric clock placed in the master-clock circuit of the Bureau. It is so arranged that the clock is short-circuited when current is not being supplied to the racks. REGULATION
OF ELECTROTYPING
SOLUTIONS.*
[A~STRACT.] THE second edition of this circular, which has been entirely rewritten, is devoted principally to a discussion of the effect of various factors upon the deposition of copper in electrotyping baths, based upon the literature on this subject, and upon recent investigations by the Bureau of Standards. The limits of composition of solutions, temperature, and current density are defined, within which copper having the required tensile strength and ductility may be obtained. The circular also includes conversion tables for Fahrenheit and Centigrade temperatures, metric and customary units, and specific gravity and degrees Baum& Definitions of important electrical terms are given, and also tables showing the weight and thickness of copper deposited bv a given current in a specified time. L
PROTECTED THERMO-ELEMENTS.% By Arthur W. Gray.
THE paper describes a convenient mounting for protecting laboratory thermo-elements from damage by contamination or by mechanical strains. The closed tube which covers the temperature determining end of the thermo-element has its open end cemented into one end of a flexible copper tube, through which the wires, properly insulated, pass to a head at the other end. Projecting downwards from this head is a glass tube which contains the ice junction. The head is provided with neutral binding posts for receiving the leads to the apparatus employed for measuring the eleetromo* Circular 52. Second edition. t Scientific Paper No. 276.
FROM
THE
U. S. B U R E A U
OF STANDARDS.*
R E P O R T OF T H E T E N T H A N N U A L C O N F E R E N C E W E I G H T S A N D M E A S U R E S , MAY 25-28, I915.
ON
THE report is a record of the proceedings of the Conference, which is composed of state and local weights and measures officials from various parts, of the United States. It contains, among other matters, short reports of the condition of weights and measures work in about twenty-five states; and technical papers dealing with the testing of electric meters, railroad track scale tests made by the Bureau of Standards, a method of adjusting railroad track scales, a discussion of automatic scales, system of keeping records, and weights and measures work from the standpoint of an efficiency engineer. The Conference adopted at this meeting extensive and comprehensive tolerances and specifications for weights and measures and weighing and measuring devices, which are given in the appendix of the report, together with a model state law on weights and measures, previously adopted. L I F E T E S T I N G OF I N C A N D E S C E N T LAMPS AT T H E B U R E A U OF S T A N D A R D S . t By G. W. Middlekauff, B. Mulligan, and J. F. Skogland.
[ABSTR*CT.] SINCE the year 19o8 the Bureau of Standards has inspected and tested the incandescent electric lamps which have been used in all departments of the government, amounting at present to about 1,25o,ooo lamps annually. The specifications under which these lamps are purchased are published by the Bureau as Circular ~3 and are recognized as standard by the manufacturers as well as by the government. They are used also by many other purchasers of lamps. Application of these specifications necessitates careful inspection and reliable life tests. The lamps are first inspected at the factory by Bureau inspectors, five per cent. taken at random from * Communicated by the Director. t Scientific Paper No. 265. 697
698
U.S.
BUREAU (IF STANDARDS NOTES.
[J.F.I.
each package being examined. These nmst conform to certain specified requirements as regards bulbs, bases, filaments, vacuum, etc. Lamps which pass these requirements are then run on the photometer to determine their candle-power and the watts consumed, and if the required percentage of the lamps falls within the specified limits the lamp nearest the mean value of each group of not more than 25o lamps is selected, labelled, and sent to the Bureau to represent the group on life test. Upon their receipt at the Bureau these samples, which a:t present amount to about 5ooo annually, are measured for voltage corresponding to the efficiency at which it is desired to run them on life test. A life test is said to be normal when it is run at the efficiency required by the specifications, and forced when it is run at a higher efficiency. Carbon lamps are usuallv tested at normal, while tungsten lamps, on account of their long life at normal, are forced in order to complete the test without unreasonably delaying the delivery of the lamps they represent, which must be held by the manufacturers pending the results of the test. The life is specified as the number of hours a lamp at rated efficiency will burn un,til its candle-power has become reduced to 8o per cent. of its original value. In the case of forced tests the actual life must be corrected by the proper factors to correspond to normal (rated) efficiency. In order to facilitate the photometric measurements of the life-test lamps and still secure a permanent, accurate, and, as nearly as possible, automatic card record of each lamp tested, certain modifications and additions have been made to the photometer used in this work. These include a watts-per-candle computer and a recording device by which observed values of candle-power, watts, watts per candle, and actual life are recorded on a separate card for each lamp. These records are made in such a way that life at forced efficiency may be corrected to life at normal without computation or reference to tables of factors. The test lamps, having been rated as described above, are then ready for the life racks, where they are burned at the respective voltages found until their candle-power has dropped 2o per cent. In order to obtain reliable results the voltage must be accurately adjusted and carefully regulated during the test. The Bureau's life-test electrical equipment is so designed that by a system of auto-transformation any voltage from 78 to _.06omav be obtained
May, i916. ]
U.S.
BUREAU OF STANDARDS NOTES.
699
and the exact value approximated to within one-tenth of one per cent. By a Tirrill regulator this voltage is kept within the specified limits of plus or minus a quarter of one per cent. Another important element in a life test is the elapsed time of burning. This is accurately determined bv means of an electric clock placed in the master-clock circuit of the Bureau. It is so arranged that the clock is short-circuited when current is not being supplied to the racks. REGULATION
OF ELECTROTYPING
SOLUTIONS.*
[A~STRACT.] THE second edition of this circular, which has been entirely rewritten, is devoted principally to a discussion of the effect of various factors upon the deposition of copper in electrotyping baths, based upon the literature on this subject, and upon recent investigations by the Bureau of Standards. The limits of composition of solutions, temperature, and current density are defined, within which copper having the required tensile strength and ductility may be obtained. The circular also includes conversion tables for Fahrenheit and Centigrade temperatures, metric and customary units, and specific gravity and degrees Baum& Definitions of important electrical terms are given, and also tables showing the weight and thickness of copper deposited bv a given current in a specified time. L
PROTECTED THERMO-ELEMENTS.% By Arthur W. Gray.
THE paper describes a convenient mounting for protecting laboratory thermo-elements from damage by contamination or by mechanical strains. The closed tube which covers the temperature determining end of the thermo-element has its open end cemented into one end of a flexible copper tube, through which the wires, properly insulated, pass to a head at the other end. Projecting downwards from this head is a glass tube which contains the ice junction. The head is provided with neutral binding posts for receiving the leads to the apparatus employed for measuring the eleetromo* Circular 52. Second edition. t Scientific Paper No. 276.