* I LEEDS & NORTHRUP COMPANY I INTRODUCTION The Macbeth Illuminometer was developed by the Leeds & Northrup Company in con- junction with. Looking for Macbeth illuminometer? Find out information about Macbeth illuminometer. A type of portable visual photometer in which the light to be measured is. The accuracy of the Macbeth illuminometer was studied by measuring a known source. The mean of a number of measurements from a number of operators.
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In making this check, there is no need for a dark room or any auxiliary photometric apparatus.
Macbeth Illuminometer – Physics Museum – The University of Queensland, Australia
Article tables are available to subscribers only. All flexible cord ends are made up with set screw con- nections so that new cords may be substituted without trouble.
Holding the illuminometer vertical, sight through the two slits near the bottom of the tube and adjust the rack up and down until the center of the filament is in line with illuminomerer centers of the slits.
Assuming that the illuminometer has been calibrated, place the test plate at the point in the plane horizontal or inclined where a measurement is desired. In that event to obtain a balance judgment is required as to when the two fields are of equal brightness.
Instrument consists of three main parts: When this balance is obtained note the mil-ammeter illumniometer on the illumjnometer standard.
Equations displayed with MathJax. The macbety was originally derived from the amount of light given by a sperm candle burning under certain fixed conditions, but has now been standardized so that it is an international unit. With the Macbeth Illuminometer as ordinarily used, that is, placing the test plate in the plane where measurements are being made, the operator can stand upright in a normal position when making tests.
Vertical distribution curves may be obtained from lamps by rotating them around a horizontal axis through the lamp center, or if the lamp cannot be rotated, by fastening the test plate upon an arm which may be rotated vertically about the lamp as a center. The interior parts, after standardization, can be effectively sealed. This attachment consists of a light weight metal elbow or horn with screening diaphragms and a mirror set at an ,acbeth of 45 degrees.
If dry cells are to be used, two No. Journal of the Optical Society of America Vol. Full text of ” Macbeth illuminometer.
Cited by links are available to subscribers only. In each case take several settings in order to obtain average values. Illumknometer the mil-ammeter is thrown from one circuit to the other a resistance is auto- matically thrown in the circuit from which the mil-ammeter has been removed, this resistance being just equal to the resistance of the mil-ammeter, thus avoiding a change of current through either lamp.
Citation lists with outbound citation links are available to subscribers only. Cross Section of Illuminometer explained later, this index mark is adjustable to allow for variations in filament position mafbeth different working standard lamps. Around the edges of the wooden base are six plug connectors; one of these is for the attachment of the working standard, a second for the attachment of the reference standard, and the four remaining ones for battery connections.
Login or Create Account. When using a screen in Slot 1 the scale reading should be multiplied by the factor given in the certificate for the screen. Every effort has been made to co-ordinate properly the qualities of compactness, light weight, accuracy, completeness and cost.
Cited By You do not have subscription access to this journal. A Lummer-Brodhun cube is mounted in the rectangular head. Connect the Reference Standard to the receptacle marked A and the Illuminometer to the receptacle marked B, using the flexible cords provided for this purpose.
Full text of “Macbeth illuminometer.”
The construction of the Reference Standard is shown in Fig. View the test plate through madbeth telescope, turning the knurled handle on the lower end to shift the working standard nearer to or away from the prism until a balance is secured, i.
Thus the user calibrates the instrument for himself, when and where he pleases, and does not depend upon the factory calibration.
References You do not have subscription access to this journal. This rod is seen projecting from the bottom of the tube Figs. The candle-power is the unit in which the intensity of a source of light in any one direction is measured.
If external batteries are being used they should be con- nected by means of the flexible cords to the proper receptacles in the controller. In actual use the working standard current is to be kept at the value determined by this check test. Percentages of total brightness measurements falling within deviation ranges.
The mean of a number of measurements from a illumonometer of operators gives a precise estimate of brightness. Further it is not a practical material to use for test plates.
Macmillan and Co Ltd, London,p. Right click equation to reveal menu options. The lamp used is seasoned and is run at such low efficiency macbwth for such short times as to insure the greatest possible constancy. Norman Macbeth, consulting illuminating engineer. This “personal equation” is practically eliminated in the Macbeth Illuminometer as every user calibrates his own instrument and does not have to use a calibration which may have been correct for the person who calibrated the instrument in the laboratory, but illumonometer is not correct for him, 4.
One mean spherical candle-power equals