* 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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All these parts are mounted upon a hard-rubber plate, which is in turn mounted upon a hardwood base. By the use of the reference standard, personal errors are eliminated, for each observer makes his own calibration of the illuminometer. If the surface under obser- vation is of exactly the same color as the light from the working standard the line of demarkation between the two fields will disappear, when a balance is obtained. Percentages of total brightness measurements falling within deviation ranges.

An important advance, however, has been made beyond previous practice.

Replace the lamp housing and then the cap carrying the rack. This rod is seen projecting from the bottom of the tube Macebth. Arrange suitable screens to cut off all light illhminometer the test plate except that coming directly from the source under test, or make the measurement in a dark room. When using a screen in Slot 1 the scale reading should be multiplied by the factor given in the certificate for the screen.

The aperture opposite the telescope is aimed or pointed toward the test plate, or any surface of which the brightness is to be measured. Article tables are available to subscribers only.

Journal of the Optical Society of America

The battery may weigh from 1H to 4 pounds, depending upon the kind and size of cells used. Measure the illumination upon the test plate in the manner previously described.

If the light source does not emit equal amounts of light in all directions the average is obtained and is known as the mean spherical candle-power. When measurements are being made at, say, a inch height this necessitates a illuminometerr cramped tiring position of the operator when reading the illu- minometer.


Curve B represents the results from block magnesium carbonate. There is now an illumination upon the test plate corresponding to the value given in the certificate. Please login to set citation alerts.

Macbeth illuminometer | Article about Macbeth illuminometer by The Free Dictionary

The lamp used is seasoned and is run at such low efficiency and for such short times as to insure the greatest possible constancy. Vertical distribution curves may be obtained from lamps by rotating them around a horizontal axis through the lamp center, or if ilkuminometer lamp cannot be rotated, by fastening the test plate upon an arm which may be rotated vertically about the lamp as a center.

You may subscribe either as an OSA member, or as an maccbeth user of your institution.

Brightness Enhancement in Intermittent Light: On the outer ends of these leads are plug connectors. References You do not have subscription access to this journal.

OSA will be closed for the holidays from 21 December One of the accessories within the case is a white test plate, with essentially constant brightness from all angles of observation. Use of Absorption screens Fig. Citation lists with outbound citation links are available to subscribers only. The controller is shown in Fig. The Reference Standard may be returned to the factory or to the Electrical Testing Laboratories for careful standardization at a nominal fee.

These screens are made of Wratten filters which may be placed one side or the other of the Lummer-Brodhun cube, thus widely extending the normal range of the instrument. Privacy Terms of Use. A direct and simple means is provided for standardizing the Mazda working standard lamp within the instrument.

Macbeth Illuminometer – Physics Museum – The University of Queensland, Australia

Tables 4 You do not have subscription access to this journal. The total range of the instrument with the two screens ordinarily provided is from about.

Morris, and Forrest L. This important preventive of carelessness cuts in resistance in the two lamp circuits and prevents passing too much current through the lamps. The construction of the Reference Standard is shown in Fig.


It is supplied with a shoulder strap for convenience of operation and observation when using the instrument. All parts involved are metal. All optical parts may be readily removed for cleaning.

The distance of the observer from the test plate will not introduce any error so long as the inner field of the Lummer-Brodhun cube is com- pletely illuminated, or in other words, the distance between the illuminometer and the test plate is immaterial provided illuminometr distance is not so great that the surroundings of the test plate appear on the inner field of the Lummer-Brodhun cube.

At 30 feet the diameter of the field is 3 feet.

The accuracy of the Macbeth illuminometer was studied by measuring a known source. For brightness of a high order it is usually stated in candle-power per square inch or per square centimeter, although for reflecting surfaces of a lower order of brightness candle-power per square foot or per square meter has been found to result in more appreciable values.

Click here to see what’s new. 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.

Colour matching filters for Macbeth illuminometer

Enoch, and William R. You do not have subscription access to this journal. Deviation Percent of measurements Percent Brightness in ft-L 0 2. With the equality of brightness type of Lummer-Brodhun screen when looking through illuminlmeter telescope there will be seen two concentric fields.

A sphere of one foot radius with a one spherical candle-power source at its center will receive an incident illumination of one foot ikluminometer at all points over its inner surface.

A recent example of this is the adoption of the Macbeth Illuminometer for use with the Absolute Reflectometer, developed at the U.