DE198290C - - Google Patents

Description

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IMPERIAL

PATENT OFFICE.

PATENT LETTERING

CLASS 42 L GROUP

G.WILHELM RUHMER in BERLIN.

Selenium photometer. Patented in the German Empire on July 3, 1906.

The selenium photometer forming the subject of the present invention should be particularly accurate Measurements' can be achieved. This is done by using two flat selenium cells that are light-sensitive on one side, which are arranged so that the first selenium cell during a phase of the measuring process from the light source to be measured, the second selenium cell from the light source of known intensity, in the second phase the second selenium cell from the light source to be measured, the first selenium cell from the known light source being affected. Since in each case the effects of both light sources at the same time affect the position of the pointer of the zero instrument, so a significant faster reacting and therefore much more sensitive zero instrument used than in the case of using only one selenium cell.

In the accompanying drawing is a special one

Embodiment of the invention shown.

The two selenium cells S ₁ and S ₂ are open

a rotating axis between the light source L to be measured and the comparison light source /. The current from a battery B enters the selenium cells through a slip ring a attached to the rotating shaft and goes through the same and the commutator b, c to the differential windings of the galvanometer G and back to the battery.

During half a revolution, the selenium cell S ₁ faces the light source L , the current flowing through it goes through the left-hand winding of the differential galvanometer, at the same time the selenium cell S ₂ faces the light source / and the current flowing through it goes through the right-hand winding of the differential galvanometer.

After half a revolution, the selenium cell S _{1 is} turned towards the light source / and the selenium cell S. _{2 is} turned towards the light source L; the current of the former flows through the right-hand winding, the current of the latter through the left-hand winding of the differential galvanometer. >; The pointer of the same is therefore subject to the differential effect of the two selenium cell currents at every moment; the magnitude of the resulting deflection, assuming the cells are identical, is dependent on the difference in the illuminations of the two cells by the two light sources and becomes zero when this is zero. By shifting the selenium cell arrangement or the light sources on a photometer bank, this zero position and thus the adjustment of the light sources can be achieved.

The distances between the light sources and the selenium cell arrangement then result in in known way the intensity of the light source to be measured in relation to .die comparison light source.

By training the zero instrument used in such selenium photometers A contact relay allows the setting of the light sources by a simple mechanical Arrangement automatically effect what. for many purposes, e.g. B. for a registering Photometer, is beneficial.

Claims (2)

Patent claims: ι. Selenium photometer, characterized by the use of two selenium cells, their light-sensitive areas alternately from a known and unknown light source Intensity are influenced, and in which the reading · the equality of both Effects of light on the cells through the zero setting of the pointer of an electric watch Zero instrument. 2. Embodiment according to claim i, in which the null instrument as a contact relay is designed, for the purpose of automatically bringing about the adjustment for equality of the exposure to light. 1 sheet of drawings.