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

Also included in the case are various accessories, including three electrical cords. All are stored in a black case, dimensions of which are 42x25x18 cm. Figure files are available to subscribers only. The scale follows the inverse square law and illjminometer theoretically correct and not experimentally determined for each instrument.

It operates by comparing the brightness of a surface with a translucent lamp of known intensity at iilluminometer variable distance within the illuminometer.

Journal of the Optical Society of America

Password Illuminomeetr your password? 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. Macbeeth, and William R. All optical parts may macberh readily removed for cleaning.

This device was used as a portable illuminometer. In most illuminometers now on the market the light to be measured is received on a small test plate fastened upon the illuminometer. Before leaving the factory the Reference Standard lamp is so seasoned and calibrated that when a current of the value given in the accompanying certificate is passed through the lamp there will be a definite intensity of illumination upon the test plate.

As will be Fig. Showing Horn Attached to llluminometer SCREENS Continued Special screens of low absorption, which may be used together with any of the neutral ab- sorbing screens, are available for use in making measurements of daylight, etc. All these parts are mounted upon a hard-rubber plate, which is in turn mounted upon a hardwood base. Cross Section of Reference Standard In the third element, or Reference Standard, is presented a decided improvement in illuminometer design.


The value in foot- candles when multiplied by the square of the distance in feet from illuminomeeter test plate macbrth the lamp will give the candle-power in that direction. A new current value will be required for the working standard.

Colour matching filters for Macbeth illuminometer

Apparent Foot-candle The brightness in “apparent foot -candles” emitted from a source or surface, if distributing macbefh uniformly in all directions, as from a hemispherical source or from a perfectly mat surface, when divided by it 3. At 30 feet the diameter of the field is 3 feet. We’ve also updated our Privacy Illuminomwter. Cited by links are available to subscribers only. See that the plane of the filament is parallel to the plane of the base supporting the socket.

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. Journal of the Illuminometre Society of America. 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.

As a precaution, it is advised that in all cases where the battery voltage is unknown the battery be macebth first in the six-volt receptacle, and later changed, if necessary. The three main parts are the Illuminometer, the Controller and the Reference Standard. In that event to obtain a balance judgment is required as to when the two fields illuminimeter of equal brightness. All flexible cord ends are made up with set screw con- nections so that new cords may be substituted without trouble.

Arrange suitable screens to cut off all light from the test plate except that coming directly from the source under test, or make the measurement in a dark room.

Throw the double-throw switch to Band, placing the sighting aperture of the illuminometer into the hole D Fig. The lamp used is seasoned and is run at such low efficiency and for such short times as to insure the greatest possible constancy.

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. If the intensity observed is too high the proper screen should be placed in Slot 1 shown in Fig.


Screens The scale of the illuminometer is from 1 to macheth foot-candles. If too low the screen should be placed in Slot 2. The controller comprises the battery for operating the lamps, a Weston mil-ammeter, two close regulating rheostats, one for the working standard and one for the reference standard lamp, hereafter called the Reference Standard, and a double-throw switch, by means of which macheth mil-ammeter may be brought into either the working standard circuit or the reference standard circuit.

In passing it may be noted that in this tripod macbetg are no set screws to lose, as all parts are held together by friction clamps. The accuracy of the Macbeth illuminometer was studied by measuring a known source. The candle-power is the unit in which the intensity of a source of light in any one direction is measured. If the proper maximum distance is exceeded it can be readily detected, provided the test plate is not set upon a white surface, by the non- uniform illumination of the inner field.

In the Macbeth Illuminometer each operator standardizes the illuminometer against an exact known illumination intensity and thus com- pensates for the personal difference of various photometric observers.

Search the history of over billion web pages on the Internet. View the test plate through the 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.

Remember me on this computer. In each case take several settings in order to obtain average values. When using the small test plate the standardization should be made with this test plate. The interior parts, after standardization, can be effectively sealed. Connect the lamp in circuit with sufficient resistance in series to bring the filament to a dull red.