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* 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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Journal of the Optical Society of America

If you require urgent assistance, please contact Customer Service. The distance of the observer illumiometer the test plate will not introduce any error so long as illminometer 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 the distance is not so great that the surroundings of the test plate appear on the inner field of the Lummer-Brodhun cube.

Diagram of Connections of Controller By using a mil-ammeter instead of a voltmeter for the control of the lamps, there is no liability of error due to changes in contact resistances, the breaking of strands in the flexible cords, and other possible sources of difficulty.

Table I Percentages of total brightness measurements falling within deviation ranges. These screens are very easily inserted or removed. Any of these publications will be sent upon request. By continuing to use this site, you agree to illuminomter use of cookies. Contrast Thresholds of the Human Eye H.

For those who prefer a translucent test plate viewed from beneath instead of the usual opaque test plate furnished with the illuminometer, a removable cap carrying a translucent plate is furnished, which is slipped over the horn.

362 – Macbeth Illuminometer

Deviation Percent of 60 measurements by: This rod is seen projecting from the bottom of the tube Figs. Tripod Attachment This is an attachment provided for holding the illuminometer in a horizontal position on the tripod when it is desired to use the instrument for making illumination measurements with the horn and translucent test plate at the inch height. All these parts are mounted upon a hard-rubber plate, which is in turn mounted upon a hardwood base.


Insert the new lamp. Also included in the case are various accessories, including three electrical cords. A new current value will be required for the working standard.

A recent example of this is the adoption of the Macbeth Illuminometer for use with jacbeth Absolute Reflectometer, developed at the U. The reference standard consists of a metal housing in which is mounted a standardized lamp.

All flexible cord ends are made up with set screw con- nections so that new cords may be substituted without trouble. Apparent Foot-candle The brightness in “apparent foot -candles” emitted from a source or surface, if distributing light uniformly in all directions, as from il,uminometer hemispherical source or from a perfectly mat surface, when divided by it 3. Special attention has been given to the elimination of reflection in the interior of the tube.

Screens of various densities may be used, either neutral or colored, for selective absorption. January 17, Published: The total range of the instrument with the two screens ordinarily provided is from about.

All parts involved are metal. Enoch, and William R. The scale follows the inverse square law and is theoretically correct and not experimentally determined for each instrument. Instrument consists of three main parts: In each case take several settings in order to obtain average values. The scale of the instrument, at one end of the illuminometer proper, is calibrated in foot-candles, and the user standardizes it themselves to allow for the absorption of the surface.

The diameter of the field of observation is roughly one-tenth of the distance between the observer and the surface being observed.

Equations displayed with MathJax. OSA will be closed for the holidays from 21 December A Lummer-Brodhun cube is used, as it is more sensitive than any other type of screen and permits a quicker and more accurate balance. Tables 4 You do not have subscription access to this journal. In passing it may be noted that in this tripod there are no set screws to lose, as all parts are held together by friction clamps. The area of a sphere of one foot radius is The Reference Standard consists of a metal housing in which is mounted a standardized lamp, fully protected with diaphragm screens.


The controller is shown in Fig. By removing the head from the tube and then taking out two screws the cube may be removed for cleaning. Abstract The accuracy of the Macbeth illuminometer was studied by measuring a known source. It is illustrated in Fig. A cross section is shown in Fig. Percent of measurements made by each operator falling within deviation ranges. Full text of ” Macbeth illuminometer. Article tables are available to subscribers only.

As will be Fig.

If the screen is in Slot 2 multiply the scale reading by transmission value given in the certificate. Replace the lamp housing and then the cap carrying the macneth. In most illuminometers now on the market the light to be measured is received on a small test plate fastened upon the illuminometer.

These screens overcome the difficulty which has always been experienced in making illumination measurements when the color of the light under test differs greatly from that of working standard lamps.

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

If there is a color difference it will be impossible to obtain this disappearance. Not Accessible Your account may give you access. The plates furnished are of glass finished by a special process These plates may, if care is used, be washed with soap and water without any danger of changing the character of the surface.

In no case should more than six volts be applied to the controller. Password Forgot your password?