US1731134A - Photometer, principally for photographic and pyrometric purposes - Google Patents

Description

Oct. 8, 1929. F. HIRSCHSON PHOTOMETER, PRINCIPALLY FOR PHOTOGRAPHIC AND PYROMETRIC PURPOSES Filed Jan. 8, 192'! NIH llll Patented och-s, 1929 PATENT OFFICE FRANZ rrmsoiisoiv, or BERLIN, GERMANY PHOTOMETER, PRINCIPALLY FOR IE'HOTOGRAPHIC AND PYROMETRIC PURPOSES Application-filed January 8, 1927, Serial No.

tric measuring-instruments. Devices are also known, whereby the intensity of current, prevailing during the moment of measuring, is not ascertained, but a standard intensity of current fixed, from which the comparisonbrightness is obtained by achange of resist- V ances.

The value of this change in resistance indicates under certain presumptions the brightness of the lamp.

- This kind of measuringhas the disadvantage, that an equally great change in resistance must render different results, if care is not taken to eliminate faults arising from the regulating-resistance for the required measurement and obtaining a standard intensity, which depends upon theprevailing battery-tension which may vary over'dif'ferent values. The object of-the present invention is to provide an arrangement in which the value of the current flowing through the lamp during, photometric measuring, can be exactly ascertained without the employment of a special,measuring-instrument.

The advantage of direct measurement of the current resides in the elimination of the above described source of errors. My invenrent which is indirectly used as basis for further measurements as will be more clearly described hereinafter.

In the system of myinvention an independent resistance of high temperature-coefli-cient is connected with the circuit formed by the battery, regulating-resistance and photo.- metric lamp as set forth in more detail in the following specification. v A separate incandescent lamp is particularly adapted to this purpose, which is however merely used as resistance and not as source of light and is therefore hereafter referred to as a resistance-lamp. Heating of the incandescent filament of this resistancetion utilizes a fixed standard intensity of cur- 159,963, and in Germany January 14, 1926.

lamp involves a considerable increaseof its self-resistance, the value of which can serve as the criterion for the intensity of current and consequentlyelso for the brightness of the photometric lamp in the same circuit.

Another arrangement is utilized, whereby this self-resistance of the resistance-lamp can be measured. This is done in a very simple manner by disconnecting the resistance-lamp from the circuit by means of a throw-overswitch and replacing the same by a suitable adjustable resistance. v

In case of consonance of this resistance with the resistance of the resistance-lamp, the ratio of current is not altered in the total circuit and it may be thereby observed, that the photometric lamp is glowing with unchangeable brightness, irrespective of whether the gauged resistance is connected. with the circuit or the resistance-lamp. In executing. a

measurement, the photometric lamp is first ad usted to the source of light to be measured and the regulating-resistance alternately connected with the circuit in a process of substituting, by actuating a switching system. If this resistance does not correspond with the one of the lamp, this fact is observable by a fluctuation in the brightness of the photometric lamp and so, withgreat exactness, as this lamp has previously been. adjusted to the brightness to be measured, byaltering the regulating-resistance, the photometric lamp is again'brought to its former brightness and the resistance of the resistance-lamp can now be read from the position of the gauged reguletting-resistance. In practice, the gaugescale will be arranged in values of brightness 1 using the instrument as on optical pyrometer, the instrument may be calibrated in values of temperature. v I

Figure 1 is a cross-sectional view taken through the photometer of my invention; Fig. 2 is a front View of the photometer with the casing partially broken aw'ayand illustrating the switching mechanism "therein; Fig. 3 is a wiring diagram showing the arrangement' of circuits for the photometer; and Fig. 4 is a modified wiring diagram of the circuits for the photometer. Fig. 5 shows of the source of light to be measured, but in a part of the instrument in its application as pyrometer.

The photometric lamp 1 is observed through. an ocular glass 2, n the field of view of which a matt disc 3 is visible. It is arranged in well known manner behind an.

open, inside blackened tube 4 and receives thus the average brightness of the pictureangle indicated by dotted lines, Fig. 1. The blackened pipe has the purpose, to permit only such rays to strike the matt disc, emanatitch button 6 is now pressed down, (Figs s Jand 3 a transfer of electrical'connections is effected and the i'esist'ance-lamp 7 is re-.

placed by the regulating-resistance 8,.the adjustment of which serves for reading the brightness of light as above described- In using the instrument and optical pyrometer, Fig. 5, a collecting lens 3 is employed instead of the matt disc, whereby a shar picture of the object to be measured is obtained in the plane of the incandescent fila-.

ment. In this kind of employment of the instrument, the filament is not tuned on a unifo'rmly 'light back-ground as in the case of the 'pyrometer, but tuning is done in such a .manner, that the object to be measured ap? pears sharpl in the field of view.' In the d photometer or-photographic purposes, it is s not essential, to measure the lucidity of a cer- 'tain','sharply limited part of a picture, but

' thefaverage total lucidity which" is important for the exposure has to be ascertained, A

fundamental difierence' between photometer and pyrometer does not exist, as the pyrometercan, upon suitable gauging, ediately be used as photometer, if the'l cidity of auniform' illuminated surface is. to be measured,'as 'for instance the lucidity of a worktable, upon which a sheet of white paper is placed.

. Fig. 4. illustrates a modified circuitarrangement for thephotometer of my invention. The resistance-lamp 7, and the substitution regulating-resistance 8 is in this case connected in parallel to the-photometric. lamp 1. The operation of the circuitof Fig, 4 is.

the same as in connection with Fig. 3. The

4 J0 shuntv 9 of predetermined ,value 'as used in 3 may be omitted in the arrangement of 1g'. 4.; 1

' As the exactness of the measurement de-' upon the extent of the change inresistafieof theresistance-lam the latter is photometric lamp.

advantageously so selected, that its consumption of current is less than theone of the In this case, slight changes in brightness will be perceptible in the resistance-lamp in form of correspondingly. increased resistance-changes. in the other lamp. In practice, an exact syntonizing of the conditions of current in both lamps can be obtained thereby, and the shunt 9 of predetermined value connected parallel to the photometric-lamp whereby the consump-..

tion of current is increased in a manner e'xactly calculable. To the maximum bright ness coming in question for thephotometric lamp, full white heat will in this case correspond to the resistance-lamp. .This shunt 9 to the photometric lamp is illustrated in alibrations are provided on the exterior of the casing of the photometer adjacent each of the operating knobs 9. 10 which control the. effective values of resistances 5 and 8 and direct readings are taken from the instru-- ment by noting the calibrations for any selected setting.

' While I have. certain of its preferred embodiments, 'I desire that it be understood that modifications described my invention in may be made and no limitations .upon my in vention are intended other than are imposed by the scope of the appended claims.

I claim 1: In a photometer a circuit containing a battery, "a regulating-resistance, a sphiotometric incandescent lamp connected in series with said battery andreslstance, an independent resistance of high temperature coeflicient, a regulating and gauged resistance, a. switch connected incircuit with said lamp and resistances and adapted to cut out said resist-- ance of high temperature coefficient from the circuit and to cut in said regulating and gauged resistance into the'circuit'for efle'cting photometric measurements.

2. Ina p otometer a circuit containing a battery, a iregulating-resistance, a photometric ncandescent lamp connected in series with said battery and resistance, a second in- 'candescent lamp, a regulating and gauged v resistance, a switch connected in circuit with said lamp and resistances and adapted to cut .outsaid second incandescent lamp from the circuit and to cutin said regulating and ing photometric measurements.

*3. In a photometer battery, a regulatin -resistance, a photometric incandescent lamp connected in series with said battery and resistance, a second incandescen't lamp, said second lamp having a smaller. consumption of current than said photometric lamp, a regulating and gauged circuit containing a gauged'resistance into the circuit for efiect-.-

resistance, aswitch connected in circuit with 'saidlamp and resistances ,andjadapted to 'cut out second incandescent lamp from the circuit and to cut in said regulating and gauged resistance into the circuit for eflect ing photometric measurements.

4. In a photometer a circuit containing a battery, a regulating-resistance, a photoa metric incandescent lamp connected in series 7 with sald battery and resistance, an lndependent resistance of high temperature 00- efficient, a regulating and gauged resistance,

a switch connected in circuit with said lamp and resistances and adapted to cut out said resistance of high temperature coeflicient from the circuit and to cut in said regulating and gauged resistance into the circuit,.and a shunt resistance connected in parallel to said photometric lamp in said series circuit.

5. In a photometer a circuit-containing a battery, a regulatingresistance, a photometric mcandescent'lamp connected in series 7 with said battery and resistance, a second.

incandescent lamp, a regulating and gauged resistance, a switch connected in circuit with said lamp and resistances adapted to cut out said second incandescent lamp from the circuit and to cut in said reghlating and gauged resistance into the circuit, and a syntonized shunt resistance connected in parallel to said photometric lamp in said series circuit 6. In-a photometer a circuit containing a battery, a regulating-resistance, a photometric incandescent lamp normally connected in a series circuit with said battery, a second incandescent lamp, said second lamp having

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