Ecological situation and ecological problems of cities

The state of the environment is one of the most important parameters that determine the quality of life of the population on the territory of the municipality.

The ecological safety of the territory is an essential component of public safety, therefore, the municipal authorities, especially in cities with an unfavorable ecological situation, must develop and implement local environmental policy, coordinated with the environmental policy of the state and aimed at protecting the environment from adverse man-made impacts. Implementation of an effective municipal environmental policy has a positive effect on the environmental situation not only in a particular municipality, but also in the region and in the state as a whole. And vice versa, a municipality with an unfavorable environmental situation, as a subsystem of the state and the region, has the right to count on the participation of the state and on the attraction of its resource capabilities to correct that R1LI of a different situation.

The severity of environmental problems, the need to ensure environmental safety and rational use of natural resources are recognized today all over the world. The aim of the state policy of the Russian Federation in the field of environmental protection and nature management is a balanced solution of socio-economic and environmental problems in the interests of present and future generations. The main environmental pollutants in municipal areas are shown in the figure. Enterprises that extract and process minerals destroy the soil layer, pollute it with waste, violate the groundwater regime, sometimes completely destroy small rivers. Energy utilities that use a variety of fuels are the largest sources of air pollution. Industrial enterprises using backward technologies that do not provide an integrated and waste-free (or low-waste) use of all types of resources, pollute the air basin, water bodies and the soil layer with various types of industrial waste. This is especially true for enterprises in the chemical, metallurgical and some other industries. At the same time, one cannot fail to note the desire of individual economic entities to get the most from the use of the natural resources of the respective territories with a minimum of responsibility for the state of the natural environment.

Automobile transport is a particularly dangerous air pollutant, since it operates in the immediate vicinity of residential buildings and crowded places.

The ecological situation is characterized by the following components.

The solution to many scientific and technical problems is associated with measuring the time intervals separating two characteristic moments of any process. Time interval measurements are necessary in the development and testing of all kinds of delay and synchronization schemes, in the study of digital systems, multichannel time division systems used in communications and radio telemetry, telecontrol and automatic switching devices, equipment used in nuclear physics, computer technology, etc. Such measurements are especially needed in instrument making, since in many cases the conversions of analog values ​​into a digital code used in it are carried out as a result of an intermediate conversion of the measured physical quantity into a time interval.

Methods for measuring time intervals are varied. The most well-known methods include discrete counting methods for converting a time interval into a digital code, time base, zero and coincidence. The process of measuring time intervals can be accomplished by many methods. Let's take a look at some of them.

1) Sequential counting method. The measurement consists in comparing the measured time interval Dtx with a discrete interval that reproduces the unit of time. For this, the measured interval Dtx is filled with pulses with a known exemplary repetition period Trev<

For the hardware implementation of the described method, a generator of counting pulses and a counter are required, between which a circuit must be included that opens the counter for the time Dtx. This function is performed by a time selector, which is a logical AND gate (Figure 1).

The counting pulses, continuously arriving at input 1 of the time selector, can only pass into the counter when a strobe pulse is applied to the input 2 of the selector. It is formed from the signal under investigation by the device contained in the formation and control unit. During the action of the strobe pulse, the duration of which is equal to the measured interval Dtx, the counter counts the pulses of the generator. The number of impulses recorded by the counter and observed with a digital display device, unambiguously corresponds to the measured interval Dtx.

In measuring technology, a pulse that cuts out a section of a pulse sequence or sets the counting duration is usually called a time gate.

In the same way, you can measure the duration of a rectangular pulse phi. In this case, the pulse under investigation is fed directly to input 2 of the selector. Time gates are obtained equal to phi duration.

The time interval can be converted to a proportional number of pulses and using a shock generator. To do this, a strobe pulse must be applied to the input of the latter, the duration of which is equal to the measured time interval, i.e. fstr = Dtx. During the action of the strobe pulse fstr, the generator generates a packet of pulses, the number of p of which is a single-valued function of the frequency of the generated signal and the duration of the strobe pulse: p = fstr F.


2) Measurement by comparing time intervals

The time interval meter (TIE) is designed to measure the time intervals of periodic processes in the microsecond range of durations. The operation of the device is based on the compensation method for measuring time intervals. The measured interval is compared with the known one; in this case, the known time interval is set by the source of time shifts (IVS), and the moment of compensation of the measured time interval by the exemplary one is fixed using an oscillographic indicator. The process of measuring time intervals is as follows: the beginning of the measured interval supplied to the input of the vertical deflection system of the indicator is aligned with the target mark on the CRT screen. Then, by changing the delay of the delayed pulse of the IVS, which triggers the scanning of the indicator, the end of the time interval is aligned with the same mark. The measured interval is equal to the value of the delay change. The source of time shifts allows you to get two pulses with an adjustable time shift between them: a trigger pulse - to start the device under test; delayed impulse - to start the waiting sweep of the IVI cathode-ray indicator. The principle of operation is illustrated by the block diagram (Figure 3).

The crystal oscillator is designed to create a reference pulse train. The frequency divider generates pulses that determine the repetition period of the output pulses. With the help of variable delay blocks J and JJ, the delay is discretely performed after 100 ns of the triggering and delayed pulses in the ranges of 0 - 900 ns and 0 - 999900 ns, respectively, by selecting the required pulses of the 10 MHz reference sequence. The variable delay is designed to cover the 0-100 ns delayed pulse time offset range. Moreover, discrete shifts of 10 ns are created using a cable delay line, and shifts are discrete after 1 ns and smoothly using an electronic delay circuit. Selectors are designed to eliminate the instability of the variable delay blocks Y and YY. The blocks interact in the following way. The repetition period of the output pulses after the divider determines the repetition period of the output pulses of the ICS (starting and reference). By this, the pulses open the inputs of the Y and YY delay blocks in the channels of the trigger and delayed pulses, to which the reference pulses are supplied. The blocks count the required number of pulses corresponding to the set delay and open the selectors. The required reference pulses are selected, which in the channel of the triggering pulse are fed directly to the output shaper, and in the channel of the delayed pulse - preliminarily to the electronic delay circuit (delay YYYY). The described method for measuring time intervals is implemented in the I2-26 meter, which measures the delay between identical signals at the same level in the range from 10 · 10-9 to 10 · 10-3 s.

3) Vernier method. Vernier meters are widely used to measure time intervals with subnanosecond resolution. The most common are combined meters, in which the time interval is "coarsely coded" by the pulses of the reference generator, and the interpolation of the segments between the boundaries of the interval and the fronts of the pulses of the reference generator is performed by the vernier method. For such meters, the urgent task of ensuring accurate matching of the main and interpolating scales, which is solved by rather complex technical methods.

This problem is absent when using the "modified" vernier method, in which the counting of the reference oscillator pulses is performed between the moments of coincidence of the phases of the reference and vernier signals. Its main advantage is a significant reduction in error? 2 ..

Mirsky G. Ya. Electronic measurements 4th ed. Rev. and add. M. Radio and communication, 1986.440 p. silt A.S. 9711527328 RU 2127445 C1 cl. G04F1004 RF High-speed vernier meter of time intervals Gurin E. I Dyatlov L. E Konov N. N Nazarov V. M. published 03.10.1999 AS 9711527328 RU 97115273 A class. G04F1004 RF

In this article, a device for measuring time intervals was developed. By assignment, the time interval can be within 1ms - 32C.

To measure the time interval between two events, it is necessary to "fill" the measured interval with pulses, and then count the number of pulses.

When applied to a microcontroller, this means:

By defining an event corresponding to the beginning of a time interval, start a "generator" that produces a sequence of pulses of a certain duration,

Arrange the counting of pulses for a given sequence,

On the event corresponding to the end of the time interval, stop the "generator"

- "issue" the value of the number of pulses to the specified ports,

- "reset" the value of the impulse counter

Functional diagram of time intervals measurement

Description of the algorithm of the device.

At the beginning of the program, all interrupt vectors of this processor are listed, the first interrupt is the reset vector ( rjmp RESET).

In this subroutine, the necessary peripheral nodes of the microcontroller are initialized, namely:

Port A is configured to output

Port C is configured to output

Port D configurable for input

Configurable interrupt int 1 (pulse decay interrupt)

Configurable interrupt int 0 (edge ​​interrupt)

The top of the stack is determined

The initializing part of the program ends with the command SEI - permission to work interrupts

Upon the arrival of the pulse front (at the output int 1 (PD 3)), an interrupt is generated int 1, the command counter "goes" from the main cycle to the interrupt vector table at the address $ 0004, there is the command to go to the interrupt handler EXT _ INT 1.

In the interrupt handling routine, the timer-counter T0 is adjusted.

The timer is set to the number to be compared (125), the prescaler value (8), and the operating mode (reset by coincidence). This means that the value in the counter will increase for eight cycles of processor operation. When it reaches 125, (125 * 8 = 1000, with a clock frequency of 1MHz, the clock period reaches 1 μs, 1000 μs - 1ms), a T0 coincidence interrupt will occur. Thus, every 1ms, T0 will trigger an interrupt. Team reti , the interrupt handler ends, the program counter returns to the main loop (where the interrupt was).

Every 1msT0 triggers the TIM0_COMP interrupt. In this interrupt, one operation is performed - increasing the register pair Z per unit. This is where the interrupt ends.

When the pulse decays (on the int0 (PD2) pin), an int0 interrupt is generated. In this subroutine, the contents of the index register Z is copied to ports (A and C), then the contents of the counting register are reset to zero, followed by the timer-counter T0 (0 is written to the control register of the counter). This ends the interruption.

Basic electrical diagram

There are two main methods for measuring the period and time intervals: oscillographic and electronic counting.

Measurement of time intervals with an oscilloscope is performed on the oscillogram of the voltage under investigation using a linear sweep. Due to significant errors in counting the beginning and end of the interval, as well as because of the nonlinearity of the sweep, the total error in measuring time intervals is a few percent. A much smaller error is inherent in specialized meters of time intervals with a spiral sweep.

Currently, the most common electronic counting methods for measuring the period and time interval. When measuring very small time intervals, conversion methods are convenient. Based on these methods, interval multipliers are created - devices that allow you to expand the measured interval by a specified number of times. Multipliers are often used in conjunction with electronic counting devices.

10.1 Electronic Counting Time Interval Meter

The block diagram of the time interval meter is shown in Fig. 6.1,. The investigated voltages U x 1 and U x 2 are supplied through two channels to the forming devices. When these voltages reach the reference levels U 01 and (U 02, short pulses U H and U K appear at the output of the shaping devices, corresponding to the beginning and end of the measured time interval Tx. These pulses act on the trigger, the output pulse of which for the time Tx unlocks the selector.

During the duration of the pulse, the counting pulses with a known period T 0, coming from the generator, are fixed by the counter.

Their number N is proportional to the measured time interval and is read from the reading device,

The circuit of the period meter differs from the one considered in that the pulses of the beginning and end of the interval, equal to the repetition period of the voltage under study, are formed in one channel, and the second shaping circuit is absent.

The period of the counting pulses T 0 is selected as a multiple of 10 - k, s, where k is an integer.

The systematic component of the instability of the counting pulses can be reduced by periodically adjusting the generator frequency.

The discreteness error, to reduce it, the generator frequency should be increased, the maximum value of which is limited by the speed of the counter used. Currently, the best commercially available meters operate up to frequencies of hundreds of megahertz. The discreteness error can be somewhat reduced by using a shock-excited counter pulse generator triggered by a UH pulse.

If the device is designed to measure the delay time in the device under test, then the pulse of the beginning of the interval can be synchronized with the counting pulses. A frequency divider, triggered by counting pulses, is introduced into the time interval meter. The pulse from the divider output triggers the DUT. Due to the instability of the time delay in the divider, the start error cannot be completely eliminated.


The measurement accuracy can be significantly improved using the special methods discussed below.

If the measured interval is repeated, then the discreteness error can be reduced by increasing the measured interval by an integer number of times or by performing multiple measurements.

10.2 Frequency measurement

Frequency measurement is one of the most important tasks in radio engineering. The frequency can be measured with a very high accuracy, therefore, methods for measuring various parameters with their preliminary conversion into frequency and measuring the latter have become widespread.

There are the following basic methods for measuring frequency; electronic counting, charge and discharge of the capacitor, comparison of the measured frequency with the reference, as well as using selective passive circuits.

The electronic counting method consists in counting the number, periods of an unknown frequency during an exemplary time interval with an electronic counter, the speed of which limits the range of measured frequencies to 100 ... 500 MHz. Large frequencies have to be converted, lowering them to the specified limits. Digital frequency meters make it possible to obtain a relative measurement error of the frequency of the order of 10 -11 and less v. range up to hundreds of gigahertz.

The method of charging and discharging a capacitor consists in measuring the average value of the charging or discharging current of the capacitor, proportional to the frequency of the measured oscillation. The method is suitable for measuring frequencies up to hundreds of kilohertz with an error of the order of 1%.

Frequency measurement by comparison with the reference frequency can be performed in a wide frequency range, including microwave. The measurement error depends mainly on the error in determining the reference frequency and can be up to 10 -13.

Frequency measurement using selective passive circuits: resonant circuits and resonators is reduced to tuning the circuit to resonance, the value of the measured frequency is read from the scale of the tuning element. The measurement error is up to 10 -4.

Thus, the most accurate results are obtained by electron counting and comparison methods, which is due to the presence of quantum frequency standards, the best samples of which are characterized by frequency instability up to 10 -13. For example, hydrogen frequency standards produced by the industry make it possible to obtain exemplary frequencies with an instability of 5 ... 10 -13 per day.

Making accurate measurements requires knowing not only the nominal value of the reference frequency, but also some other parameters that characterize its instability.

10.3 Electronic counting method of frequency measurement

The electronic counting method is based on counting the number of pulses with an unknown repetition rate fx at a known time interval stable in duration. The simplified block diagram of the frequency meter (Fig. 8.2, a) is similar to the circuit of the time interval meter.

The frequency of the crystal oscillator is chosen to be n * 10 k Hz, where k is an integer and the division factor n is a multiple of ten. Therefore, the number of pulses recorded by the counter N corresponds to the value of the measured frequency in the selected units. The f 0 value is read from the reading device of the device.

Frequency measurement by charging and discharging a capacitor

This method is the basis for the operation of the frequency meter, the diagram of which is shown in. rice. 8.4, a. The voltage U g with a frequency f x is fed to the amplifier-limiter (Fig. 8.4, b). Its output voltage U 2, in the form of rectangular pulses, acts on a circuit consisting of a capacitor C and diodes D1 and D2. Let at the initial moment of time the voltage across the capacitor Uc = U2- The charge time constant is chosen much less than half the period of the input voltage. The average value of the capacitor charge current passing through the diode D1 and the magnetoelectric device,

is proportional to the frequency fx, therefore the scale of the magnetoelectric device is calibrated in the values ​​of the measured frequency.

Frequency meters of the considered type operate in the range from tens of hertz to units of megahertz. This frequency range is covered by several subranges with different measurement limits. The transition from limit to limit is achieved by changing the capacitance, which is selected so that at the limiting frequencies of the subranges, the average current of the device is sufficient to deflect the arrow to the full scale.

Frequency measurement by comparison with a reference

In this method, the measured frequency fx is compared with the known frequency f 0 of the oscillator of the reference frequency. Rebuilding the latter, one achieves the fulfillment of equality

where Δσp1 is the frequency comparison error.

The frequency comparison error depends on how the frequency equality is indicated. In some devices, a mixer and headphones are used to indicate equality (Fig. 8.5, a). Under the influence of oscillations of the reference and measured frequencies, oscillations of the combination frequencies of the form mfx ± appear in the mixer. nf 0, where m and n are integers. If the difference frequency signal falls within the bandwidth of the headphones, the operator hears the tone of that frequency. By changing f 0, the lowest tone should be achieved, which for various types of headphones is tens of hertz.

Since the frequency is unknown during measurements, the method is ambiguous and before measurements it is necessary to know the approximate value of f x. The considered method of measuring frequencies is sometimes called the zero beat method.

Measurements are made using the fork method. The comparison error in this case is 10 ... 30 Hz.

10.4 Frequency measurement with selective passive circuits

Measurement in this way is reduced to tuning the selective circuit to the signal frequency. The frequency is measured by the position of the tuning element. Such circuits can be bridge circuits and oscillatory circuits. Currently, bridge frequency meters, the scope of which is limited to low frequencies, are completely replaced by other types of instruments. Only frequency meters using a resonant circuit, called resonant wavemeters, have found practical application. These simple instruments cover a frequency range from hundreds of kilohertz to hundreds of gigahertz. A simplified diagram of a resonant wavemeter with a circuit is shown in Fig. 8.8. The voltage of an unknown frequency fx through the communication coil Lsv is supplied to a circuit consisting of an exemplary coil L and a variable capacitor C. The circuit is tuned by changing the capacitance, The state of resonance is determined by a magnetoelectric device according to the maximum voltage on a part of the coil. The measured frequency value is read from the capacitor scale.

The error in measuring the frequency using resonant wavemeters is determined by the following main factors: calibration error, instability of the resonant frequency of the oscillatory system, the influence of communication with the generator and indicator, inaccuracy of resonance fixation. The calibration error can be large if malfunctions appear in the adjustment mechanism, which has a rather complex design. This error increases due to wear of the mechanism parts, the appearance of distortions and backlash.

Due to the connection with the indicator and the source of the measured frequency, active and reactive resistances are introduced into the resonator. The growth of active losses decreases the Q-factor, and the inconstancy of the introduced reactance leads to a shift in the resonance. A decrease in errors due to the influence of the indicator and the signal source is achieved by reducing the connection. But at the same time, the voltage supplied to the detector decreases and amplifiers have to be introduced into the circuit after the detector.