SU873747A1 - Device for measuring radiation - Google Patents

Description

The invention relates to thermal radiation detectors designed to measure powerful radiant fluxes in the optical wavelength range.

Known receivers of intense radiation fluxes with sensitive elements in the form of hollow pyroelectric spheres and cones in which the density of the studied radiation flux incident on the sensitive element decreases due to reflection of the beam or the location of the receiving area at an acute angle to the incident flux [1].

However, such an expansion of the upper limit of the measured powers is currently insufficient, for example, in connection with the creation of super-powerful laser systems.

Closest to the proposed is a device for measuring radiation, containing a modulator - attenuator, a pyroelectric radiation detector, matching cascade and recording device | [2].

The disadvantage of this device is that the upper limit of the power does not exceed 100 W / cm ² due to the fact that a powerful signal takes the receiver beyond its linear amplitude characteristic.

In addition, the device has a low threshold sensitivity, so that in general, the dynamic range does not exceed ΙΟ ⁶ —10 ⁷ .

The purpose of the invention is the expansion of the upper 5 border of the range of measured powers.

This goal is achieved by the fact that in a device for measuring radiation containing a modulator - attenuator, a pyroelectric radiation detector, matching cascade and recording device, the modulator - attenuator is made in the form of two identical coaxial disks - choppers, one of which is directly connected to the sound generator, and the other through an amplitude-phase converter, the latter is connected to an average power amplifier, which, in turn, is connected to a matching cascade, while the electric constant I time of the input circuit of the receiver t _E l satisfies the relation w ^w max where Wcp is the average allowable radiation power incident on the receiver;

W _M a «c is the maximum measured power of continuous radiation fluxes;

T is the modulation period.

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In FIG. 1 shows a block diagram of a device for measuring radiation; in FIG. 2 and 3 - diagrams of power W and voltage U.

The device contains a pyroelectric receiver 1, a matching stage 2, an average power amplifier 3, a recording device 4, an amplitude-phase converter 5, an audio generator 6, motors 7 and 8 of the attenuator - modulator 9.

The device operates as follows.

The radiation flux W, interrupted by two attenuators — the modulators 9, falls on the receiver 1, the signal removed from the receiver after the matching stage 2 is fed to the recording device 4 and in parallel to the medium-power amplifier

3. As shown in FIG. 2, the measured continuous flux of radiation is proportional to the peak value of the sequence of periodic pulses.

In order for the device to operate in linear mode, the average power W _{cp of} the pulse train should not overheat the receiver beyond the permissible temperatures corresponding to the linearity of the amplitude characteristic.

With an increase in the measured power W _H 3m (see Fig. 3), the signal taken from the receiver, arriving at the medium-power amplifier 3, controls the amplitude · -phase 5 converter in such a way that a phase shift occurs between the two motors 7 and 8, fed from sound generator 6. Modulation of the radiation flux (see Fig. 3) becomes asymmetric, but with the same period T.

The phase shift will increase until the value of the average power W _C p dissipated in the sensitive element of the receiver reaches an acceptable value (dotted line).

In this case, the following energy equality holds: w _cp -T = w _uaKC -x _UM n (1)

In order for the radiation receiver to work in the power measurement mode and not distort the pulses, it is necessary that the electric time constant of the input circuit of the receiver TEP = PC (R, C are the total values of the equivalent resistances and capacitance of the receiver and input circuit) should not exceed the pulse duration In this case, in the optimal mode of operation

Thus, due to asymmetric modulation and its automatic control by the measured signal, it becomes possible to expand the upper limit of the measured powers by at least two orders of magnitude, while preserving the lower one.

If the value of W _{cp is} chosen with a certain margin, then errors associated with the instability of the duty cycle of the pulses are excluded, since the pulse value of the signal changes. It also weakens the accuracy requirements for the manufacture of perforations of modulators, coaxial installation and their engine backlash. Changing the modulation frequency is also not affected.

When measuring weak radiation fluxes using a range switch made, for example, on reed switches, it is necessary to increase the value of t _E l to the maximum values in accordance with equation (2).

Using the proposed device will reduce the measurement time, increase their accuracy and prevent device failures.

Estimated annual economic effect when measured will be 20 thousand rubles. on one installation.

Claims (2)

FIG. 1 shows a block diagram of a device for measuring radiation; in fig. 2 and 3 -epenes of powers W and voltages and. The device contains a pyroelectric receiver 1, matching cascade 2, medium power amplifier 3, recording device 4, amplitude converter - phase 5, sound generator 6, motors 7 and 8 attenuator - modulator 9. The device operates as follows. The radiation flux W, interrupted by two attenuators - modulators 9, falls on receiver 1, the signal taken from the receiver after matching stage 2 is fed to recording device 4 and in parallel to average power amplifier 3. As shown in FIG. 2, the measured continuous radiation flux is proportional to the peak value of the sequence of periodic pulses. In order for the device to operate in the linear mode, the average power of the Wcp pulse train should not overheat the receiver beyond the limits of permissible temperatures corresponding to the linearity of the amplitude response. With an increase in the measured power WHSM (see Fig. 3), the signal taken from the receiver, fed to the average power amplifier 3, controls the amplitude-Phase 5 transducer in such a way that a phase shift occurs between the two motors 7 and 8, powered by sound generator 6. The modulation of the radiation flux (see Fig. 3) becomes asymmetric, but with the same period T. The phase shift will increase until the value of the average power Wcp dissipated in the sensitive element of the receiver reaches (dotted line). In this case, the following energy equality W, pT W ,,, -., N is fulfilled (1) In order for the radiation receiver to operate in the power measurement mode and not distort the pulses, it is necessary that the electrical time constant of the receiver input circuit is tel (, С - total values of equivalent resistances and capacitance of the receiver and input circuit) should not exceed the pulse width. In this case, in optimal mode. Thus, due to the asymmetric modulation and its automatic control using the measured signal, be extend the upper limit of the measured capacity at least two orders of magnitude, while retaining the bottom. If the value of Wcp is chosen with a certain margin, then errors associated with the instability of the pulse duty cycle are eliminated, since the pulse value of the signal changes. It also weakens the accuracy requirements for the manufacture of modular perforations, coaxial mounting and engine backlash. Changing the modulation frequency is also not affected. When measuring weak fluxes of radiation using a range switch made, for example, on reed switches, it is necessary to increase the value of Tel to maximum values in accordance with equation (2). The use of the proposed device will reduce the measurement time, improve their accuracy and prevent the device from running out. Estimated annual economic effect in measurements will be 20 thousand rubles. on one installation. Apparatus for measuring radiation containing modulator - attenuator, pyroelectric radiation receiver, matching stage and recording device, characterized in that, in order to expand the upper limit of the range of measured powers, the modulator - attenuator is made in the form of two coaxial identical disks - interrupters, one of which is directly connected to the sound generator, and the second through an amplitude-phase converter, the latter is connected to an average power amplifier, which, in turn, It is connected to the matching cascade, while the electrical time constant of the receiver input circuit TPL satisfies the relation: where Wcp is the average permissible radiated power incident on the receiver; WwaKc is the maximum measured power of continuous radiation fluxes; T is the modulation period. Sources of information taken into account during the examination 1. USSR Copyright Certificate № 461315, cl. G 01J 5/00, 1978. 2. Kostin V.V. Thermal generator receivers of energy flows based on the pyroelectric effect. M. Electronics, 1971. with. 63 is a prototype. w, U3H W, Wtf MAZ U a IG  M wto W anp Have Ptn.S