RU1777649C - Optical density meter - Google Patents

Abstract

The invention relates to optical analysis methods and can be used to measure the exhaust smoke of diesel engines. The purpose of the invention is to increase the accuracy of measurements due to automatic correction of the base reference. By shorting the key 8, an increasing voltage is generated at the output of the inverting integrator 9, provided by the voltage imbalance of the signals of the integrator 6 and the reference voltage source 10, calculated by the adder 7. The increasing voltage shifts the operating point on the characteristic of the logarithmic converter 5, which forms a sequence of pulses whose duration is proportional to the logarithm of the ratio of the signals of the photodetector 2, amplified by the amplifier 4. and the integrator 9. In the steady state, the pulse signal of the conversion The integrator 5 integrated by integrator 6 compensates for the reference voltage, and zero voltage is set at the output of adder 7. When the key 8 is opened, the inverting integrator 9 stores the correction signal. 2 ill. with

Description

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The invention relates to optical analysis methods, and in particular, to means for measuring the optical density of a substance and can be used to measure the smoke of exhaust gases of diesel exhaust and the optical density of dusty gas streams.

The purpose of the invention is to increase accuracy by automatically correcting the base reference.

Figure 1 shows the functional diagram of the device; figure 2 is a functional diagram of the logarithmic converter of the device.

The optical density meter contains a radiation source 1 and a photodetector 2, optically coupled and placed in tubes located on both sides of the measuring channel 3, serially connected amplifier 4, a logarithmic converter 5, at the first input, an integrator 6, an adder 7 for non-inverting input, a key 8 and an inverting integrato 9, as well as a reference voltage source 10 and a pei abrasive device 11 connected to the output of the adder 7. In this case, the photodetector 2 is connected to the second input of the logarithmic pre 5, and the reference voltage source 10 is connected to the inverting input of the adder 7. Logarithmic converter 5 is made in the form of a series-connected key 12 and a comparator 13 parallel to the RC circuit 14 connected to the inverting input of the comparator 13 and the output of the key 12, with the first input the logarithmic converter 5 is the input of the key 12, and the second input is the non-inverting input of the comparator 13, the Integrator 6 is made in the form of a low-pass filter of the second order, and the inverting integrator 9 is made in the form of an operation Nogo amplifier inverting operation in a storage capacitor in the negative feedback.

The optical density meter works as follows. In the initial state, the switch 8 is open and the voltage is zero at the output of the inverting integrator 9. The pulse signal of the photodetector 2, corresponding to the radiation pulses of the emitter 1, is fed to the first input logarithmically about the converter 5. Through the electronic switch 12 of the converter 5, the signal charges the capacitor of the RC circuit 14 and forms an exponentially coupled sequence on the inverting path of the comparator 13

giving pulses, which are compared with the output voltage of the inverting integrator 9, connected to the non-inverting input of the comparator 13. As a result of comparing the voltages applied to the inputs of the comparator, a low (zero) signal level is generated at the output of the latter. This level through the integrator b is applied to the non-inverting input

0 of the adder 7 and, taking into account the voltage of the reference source 10, generates a negative voltage at the output of the adder 7.

Correction of the basic readout of the device (setting the indicator of the recording device 5 of the device 11 to the zero position) is performed when the key 8 is closed. In this case, the negative voltage present at the output of the adder 7 is connected to the input of the inverting integrator 9.

0 which generates an increasing voltage of positive polarity at the output of the inverting integrator 9. The increasing voltage applied to the input of the logarithmic converter 5.

5 contributes to the formation at the output of the comparator 13 of the pulse sequence with a repetition rate equal to the repetition rate of exponential pulses, and the pulse duration

0 at the output of comparator 13 increases with increasing voltage at the second input of converter 5.

The process of increasing the voltage at the output of the inverting integrator 9 and the pulse duration at the output of the logarithmic converter 5 will stop when the zero voltage is established at the output of the adder 7. In this case, the pulse signal of the logarithmic converter 5 integrated by the integrator 6 compensates for the reference voltage taking into account the transfer coefficient at the inputs of the adder 7. The established (initial) value of the duration

The 5 pulses of the logarithmic converter 5 is determined by the magnitude of the reference voltage. The voltage at the output of the integrator b, corresponding to the zero voltage supplied to the recording

0, the device 11 is saved when the key 8 is opened and the device enters the measurement mode. By including a storage capacitor in the circuit of the inverting integrator 9. A significant transmission coefficient of the negative feedback loop, which covers the elements of the optical density meter in the base reading correction mode, ensures high accuracy of zero setting of the inventive device.

In the measurement mode, a decrease in the amplitude of the signal of the photodetector 2 due to absorption of radiation by the medium causes a decrease in the initial pulse duration at the output of the logarithmic converter 5, a corresponding decrease in the voltage at the output of the recording device 11, which is proportional to the density of the absorbing medium in the measuring channel 3.

The advantages of the n JTHOCTH optical meter with automatic correction of the base readout are manifested to a large extent in the operational control of the smoke of gas streams with a significant content of solid and liquid aerosols. A slight shift in the basic count after each single measurement of smoke and dust caused by the deposition of gas components on the optical elements is compensated with high accuracy when the key contacts are closed. At the same time, due to the linearity of the meter conversion function, other metrological characteristics of the device are not changed. A wide range of changes in the correction voltage at the second output of the logarithmic converter 5 and a high resolution of the device over the entire range of changes in the compensation signal provide high operational and metrological characteristics of the device.

Claims (1)

SUMMARY OF THE INVENTION An optical density meter comprising an emitter and a photodetector, optically coupled and located on both sides of the measuring channel, a serially connected amplifier and a logarithmic converter, as well as a reference voltage source and a recording device, the photodetector output being connected to the amplifier input, which differs the fact that, in order to increase accuracy by automatically correcting the base count, the integrator, adder, and and an inverting integrator whose output is connected to the second input of the logarithmic converter connected to the input of the integrator output, 5, the reference voltage source is connected to an inverting input of the adder, and the output of the adder is connected to a recording device.