RU1831678C - Device for control of dust contents in gas stream - Google Patents

Abstract

Usage: technique for measuring particles in a gas stream. SUMMARY OF THE INVENTION: the device comprises an integrating element, two signaling devices, a reference signal source, a broadband amplifier and a pinhole located in front of the photodetector, and an isolation capacitor connected between the amplifier and one of the signaling devices. 1 ill.

Description

The invention relates to techniques for measuring the concentration of particles in a gas stream and can be used for. control of dust content in industrial ducts, gas pipelines, as well as in the inlet tracts of compressors and internal combustion engines.

The purpose of the invention is to increase the reliability of control by taking into account both the soiling and the dust settled in the optical channel.

This goal is achieved by the fact that an additional signaling device, a reference signal source, an isolation capacitor and an integrating element, an input are introduced into the device

which is connected to the amplifier output and the output to the excitation and control circuit of the light source and simultaneously the input of an additional signaling device, the amplifier being made broadband and equipped with an additional differential input to which a reference signal source is connected, and an isolation capacitor is connected between the amplifier and the main signaling device, wherein the optical diaphragm is made point and placed in front of the photodetector.

The drawing shows a functional diagram of the device.

The device comprises a dust collection chamber 1 with windows 5, at the ends of which a light source 2 in the form of an LED and a photodetector 4 are placed, which can be made in the form of a photodiode combined with an integrated photocurrent amplifier. In the cavity of the chamber in front of the photodetector 4 there is a point diaphragm 3. The diameter of the hole in it is defined by the concept of a point and is selected according to the condition of diffraction at its edges. In practice, at least 0.3 mm for a round hole. Deviations up to 0.6 - 1 mm are possible for structural reasons and, if not necessary, the maximum resolution. The position of the diaphragm in the chamber in front of the photodetector is selected taking into account the size and concentration of particles, as well as the parameters of source 2 and photodetector 4.

The measuring circuit contains a differential amplifier 6. source support00

with

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of the signal 12, the integrating link 9, the excitation and regulation circuit of the LED 11, the isolation capacitor 7 and two signaling devices 8 and 10. All the elements are combined and form a measuring channel covered by a deep negative feedback through the light flux with the release of pulse signals from passing dust particles and slowly varying compensating effects in the feedback loop, proportional to the accumulated dust.

The device operates as follows.

In the absence of dust, the stabilization circuit, including elements 2,4,6,9,11 and 12, maintains the luminous flux in the chamber 1 at a predetermined level, which corresponds, for example, to the initial current of the LED 2. In this case, the voltage is set at the output of the photodetector 4 equal to the reference element 12. At the output of the amplifier 6, a constant voltage level will be established. Approximately the same voltage will be at the output of the integrating link 9 (an RC circuit can be used as the latter). Signaling devices 8 and 10 - in the initial (zero) state,

When running dust and gas flow, dust particles enter through the window 5 in the dust chamber. The light flux is perturbed by the particles, which causes the appearance of voltage spikes at the output of the photodetector 4, which are amplified by the amplifier 6 and through the isolation capacitor 7 arrive in the form of pulses to the input of the detector 8, changing its state. Due to the inertial properties of the integrating element 9, the stabilization circuit does not have time to compensate for perturbations from individual particles, therefore, for short pulses, the feedback is almost open and, with a large coefficient of amplifier 6, it is possible to isolate signals caused by the smallest particles. Slowly changing perturbations, caused primarily by the deposition of dust on the elements of the opto-couple 2,4, slowly change. the output level of the output voltage of amplifier b, which is smoothed by the integrating link 9 and registered by the signaling device 10. At the same time, by

the circuit of circuit 11 increases the current of the iodine 2, compensating for the slow disturbance. Dust accumulation in the optical channel can occur as long as the constant

The voltage at the output of amplifier 6 does not go beyond the permissible limits, which can be brought into correspondence with the limiting current of LED 2 and the limiting concentration of particles in the chamber. Thus, both soaring particles and settled ones are recorded, while the point aperture provides a sufficiently small field of view of the photodetector for the resolution of individual soaking particles, and the reverse circuit

connection - high stability and control of dust deposition.

The tested models of the device confidently recorded the passage of individual particles with a size of 15-20 microns or less (up to 5 microns).

when air enters with a dust concentration of 1 mt / m, the accumulation of its maximum amount occurs after about 2000 hours of continuous operation. The minimum detectable concentration was

0.1-0.4 mg / m3.

Claims (1)

SUMMARY OF THE INVENTION A device for monitoring dust content in a gas stream comprising a dust collection chamber with an inlet window, a light source and a photo detector arranged coaxially on opposite sides of the dust collection chamber, a diaphragm, and also a light source excitation and regulation circuit, an amplifier and an indicator connected to the output of the amplifier, the input of which is connected to the photodetector, which requires that, in order to increase the reliability of control, an additional signaling device, a reference signal source, be introduced into it, a separation capacitor, and an integrating link, the input of which is connected to the amplifier output, and the output to the excitation circuit. and regulation of the light source and simultaneously to the input of the additional a signaling device, the amplifier being made broadband and equipped with an additional differential input to which a reference signal source is connected, the diaphragm is pinpointed and placed in front of the photodetector, and a separation capacitor is connected between the amplifier and the main signaling device. I dust-dusted tray at