SU1395995A1 - Method of checking stability of conversion factor of photoelectric detector of suspended particles - Google Patents

Abstract

The invention relates to a measuring and measuring technique and can be used in metrology, biology, and other fields. The goal is to increase the operational control. The stability of the recorder conversion factor is monitored continuously during the measurement process, with the background light signal being used as the calibration signal. Since the level of this signal is constant, it can be separated from the aggregate signal, which also contains pulses from the recorded particles. To do this, a filtering unit is introduced into the device; it is made in the form of a limiting amplifier with a predetermined limitation threshold, a block of a constant component of the calibration signal, and a display unit. The increase in the efficiency of monitoring the stability of the photoelectric recorder's converter's efficiency coefficient is achieved due to the continuity of control, which, in turn, increases the reliability of measurement results. 3 il. I CL SO ate co

Description

The invention relates to measurement instrumentation and can be used in meteorology, biology, chemical technology, environmental pollution control to control the stability of the conversion coefficient of photoelectric suspended particle recorders.

The purpose of the invention is to follow one of the controllability.

FIG. 1 shows a block diagram of an apparatus for carrying out the inventive method; in fig. 2 - type of signals (and,) at the output of the amplifier -} 5 limiter; in fig. 3 is a view of the signals (CHs) at the output of the DC allocation unit.

A device for carrying out the proposed method comprises a luminaire 1, a photodetector unit 2 (receiving scattered light from the so-called counting volume of the recorder, indicated in Fig. 1 by a dashed line), connected in series 25 limiting amplifier 3 with a given limitation threshold, block 4 selection of a constant component, unit 5 of comparison and indicator 6.

The method is carried out in the following manner.

The beam of light from illuminator 1 is directed to the counting volume. The photodetector unit 2 perceives light scattered on the fluctuating density of air or another gas and (or) on the elements of the optical path. This light signal is a calibration signal. In the presence of suspended particles in the counting volume, the light scattered by them is also perceived by Q as the photodetector unit 2, and the signal level from the particles of the minimum detectable size obviously exceeds the level of the calibration signal. Next, these total signals are converted by the photoreceiver unit 2 into electrical signals that are amplified a limiting amplifier 3. The amplified signal contains a component with a certain level and (Fig. 2) proportional to the level of the continuous calibration signal. The pulses from the particles are limited in amplitude by some

50

level Ug, and Ug

and.

These pulses have a duration C and an average period T of repetition, and the period T depends on the concentration of particles. At the maximum allowable

-

five

0 5

ABOUT

Q

0

five

for a photoelectric recorder, the concentration of particles due to a 10% measurement error due to the simultaneous fall into the counting volume of two or more particles is csO, 1. Block 4 allocates a constant

component of the signals from the amplifier - limiter.

In the absence of particles, the constant component of the signal (caused only by the light calibration signal) has a certain level and (and: Ujj) (Fig. 3). The presence of pulses from suspended particles leads to an increase in the level of the constant component to a certain value U,

and - and Uo - and G.

and - T-

If the relative instability of the conversion coefficient of the photoelectric recorder is acceptable (for the output signal)

--- And, where A. is a certain numberless

dimensional value, and the change in the relative level of the constant component, due only to the presence of pulses from suspended particles,

d exceeds - then for max

the allowable concentration of the bond and "and and is determined by the ratio

.

Based on this condition, a threshold is set equal to U.

Next, the DC level of the signal in block 5 is compared with a predetermined voltage range, which determines the allowable instability of the photoelectric recorder conversion coefficient.

The output of the constant component from a predetermined voltage range means that the conversion factor is out of acceptable limits, as indicated by indicator 6.

Claims (1)

Invention Formula A method for monitoring the stability of the conversion coefficient of a photoelectric recorder of weighted particles, which consists in supplying a calibration light signal to the input of the photodetector unit of the recorder and register the level of this signal at the output of the photoreceiver unit, according to the stability of which the stability of the conversion coefficient of the recorder is judged, characterized in that, in order to monitor the monitoring performance, the calibration signal is fed to the input of the photoreceiver unit continuously the magnitudes of the signals from the measured particles without changing the level of the calibration signal at the output of the photodetector unit and the constant component of the calibration signal. but well a srigL 2