SU62324A1 - Device for measuring color temperature - Google Patents

Description

The known devices for measuring color temperature have a number of significant drawbacks: the readings do not correspond to the true melting temperature, their unsuitability for continuous temperature measurement, the inability to measure the temperature of moving bodies, etc.

In the proposed device, an electronic log meter is applied, which allows to obtain a gain effect simultaneously. The photocells of the device are connected to grids through such resistances so that there is a logarithmic relationship between the voltages on the grid and the photocurrents.

Photovoltaic cells are respectively connected to successively connected to each other lamps with a braking field between the grid and the anode, which is the load of the amplifying lamp. All this makes it possible to eliminate the drawbacks of the known devices.

FIG. 1-4 shows four variants of the electrical circuit of the proposed device.

The device consists of two photoelements. 4 and 5 {fig. 1), on which the light from the source under study simultaneously falls. The currents of the photocells are amplified by means of two amplifying lamps 6 and 7, having logarithmic characteristics. Photovoltaic cells have different spectral characteristics or are supplied with light filters selected so that the maximum sensitivity of one photocell lies in the blue and the other in the red region of the spectrum. Thus, a strictly defined ratio of voltages - will correspond to each color temperature of the source. Galvano. 13 meter, whose indications are proportional to the difference in anode currents, due to the logarithmic characteristic of the latter, shows a non-mediated ratio. (or reverse to it).

Alb 62324 - 2 Since the ratio for these photocells is characterized by the blue-red ratio and, consequently, the color temperature, the galvanometer can be directly calibrated in degrees. This circuit uses a logarithmic relationship between the anode current / a and the voltage across the grid. The load resistances 9 n, 10 of two photocells 4 and 5 (with two light filters 2 and), which measure the red-blue ratio of source 1, are connected between the cathode and the grid of two amplifying lamps b and 7. As is well known, with small voltages the grid between the grid current Kc Ig and "april on the grid Vg is the following relationship: /" -: where / and a are constant.

At the same time, when grids of a sufficiently large withstand R II and 12 are included in the grid, the grid current ig is connected with the measured voltage drop and at the resistance r 9, 10 and with the photocurrent t, the voltage r

in other ways; ... Thus, between the voltage on K K

grid and photocurrent is the logarithmic dependence Oy Algnitfi, where A is constant. By observing the linearity of the anode characteristic of the lamp, the logarithmic dependence of the anode current of the lamp on the photocurrent / a Sy Blgnif is also obtained, where B is constant.

In the second circuit (Fig. 2), the logarithmic dependence of the voltage VL at the anode of the lamp on the anode current / a is used. The principle of operation of the scheme is based on the distribution of the velocities of thermoelectrons in the retarding field according to the Maxwell-Boltzmann law. According to this law, the thermionic current i is associated with the voltage of the braking FIELD V as follows:

V - (300 q: 7 / a) / „/ -GSOp81, where k, T l in are constant.

In order to create a decelerating field between the anode and the grid of lamps B and 7, a sufficient positive voltage from the batteries 14 and 15 is applied to the grids, which is slightly greater than the voltage generated at the anode by the photocurrent flowing from the lamps from two photo cells 4 and 5. If there is a braking field between the anode and the grid of the lamp, the connection between this voltage and the current to the anode will be logarithmic. Therefore, the total anodic voltage Pa on the lamp will be connected with the photocurrent by the logarithmic dependence Va - klgniip + const,

where k- “is constant.

Lamps 6 tl 7, connected in series and towards each other, represent the grid load of the amplifying lamp 8. The anode current of the last lamp varies linearly with the voltage on the grid, which is the difference between the anode voltages of lamps b and 7, and the difference is logarithms of photocurrents.

Good practical results can be obtained when testing a circuit using the grid current of an amplifying lamp, and the actual circuit (Fig. 3) is somewhat different from the circuit of Fig. 1, namely: here the photocathode is directly connected to the grid of the amplifying lamp, and the load resistance 9 and ./O and the resistance in the grid // and 12 are missing. These changes do not change the essence of the matter.

Even better results can be obtained with the circuit in FIG. 4, where a diode is used in the mode of decelerating floor and an amplifying lamp operating in the absence of grid current. When the photocell is switched on, a negative potential (relative to the cathode) is automatically established in series with a diode at the anode of the latter, the value of which varies logarithmically depending on the photocurrent. Thus, the potential difference between the two anodes of the diode is proportional to the logarithm of the ratio of photocurrents. This circuit, despite the presence of an excess element (diode), has the advantage that it allows us to obtain a more strict logarithmic relationship between the anode current of the amplifying lamp and the photocurrent and, moreover, within very wide limits.

Subject invention

Claims (3)

1. A device for measuring the color temperature of sources according to their radiation in two different parts of the spectrum, equipped with two photocells with appropriate spectral characteristics that are connected so that an appropriate instrument, for example, a logometer, takes into account the ratio of photocurrents, At the same time, the gain effect is obtained; an electronic logometer is used. 2. The form of the device according to claim 1, that is, and with the fact that, in order to use the logarithmic relationship between the anode current and the voltage in the grid of the lamps, the photo cells, respectively, are cr. connected with the grids of the lamps through such resistances that there is a log; Jp. The relation between the voltages on the grid and the photocurrents is the same. 3. The form of the device according to n. 1, characterized in that, in order to use the logarithmic dependence of the anode voltage on the anode current of the lamps, photo cells are respectively connected to successively connected opposite lamps with a braking field between the grid and the anode, which is the grid and alignment of the amplifying lamp. APL / Fug