Among the general industrial ones used to account for products and raw materials, there are common goods, automobiles, carriages, trolleys, etc. Technological ones are used for weighing products during production in technologically continuous and periodic processes. Laboratory tests are used to determine the moisture content of materials and semi-finished products, conduct physical and chemical analysis of raw materials and other purposes. There are technical, exemplary, analytical and microanalytical.
They can be divided into a number of types depending on the physical phenomena on which the principle of their operation is based. The most common devices are magnetoelectric, electromagnetic, electrodynamic, ferrodynamic and induction systems.
The diagram of the magnetoelectric system device is shown in Fig. 1.
The fixed part consists of a magnet 6 and a magnetic circuit 4 with pole pieces 11 and 15, between which a strictly centered steel cylinder 13 is installed. In the gap between the cylinder and the pole pieces, where a uniform radially directed direction is concentrated, a frame 12 made of thin insulated copper wire is placed.
The frame is mounted on two axes with cores 10 and 14, resting on bearings 1 and 8. Counter springs 9 and 17 serve as current leads connecting the frame winding to electrical diagram and input terminals of the device. On the axis 4 there is a pointer 3 with balance weights 16 and an opposing spring 17 connected to the corrector lever 2.
01.04.2019
1. The principle of active radar.
2. Pulse radar. Operating principle.
3. Basic time relationships of pulse radar operation.
4.Types of radar orientation.
5. Formation of a sweep on the PPI radar.
6. The principle of operation of the induction lag.
7.Types of absolute lags. Hydroacoustic Doppler log.
8.Flight data recorder. Description of work.
9. Purpose and operating principle of AIS.
10.Transmitted and received AIS information.
11.Organization of radio communications in AIS.
12.Composition of shipboard AIS equipment.
13. Structural diagram of ship's AIS.
14. Operating principle of SNS GPS.
15.The essence of differential GPS mode.
16. Sources of errors in GNSS.
17. Block diagram of a GPS receiver.
18. Concept of ECDIS.
19.Classification of ENC.
20.Purpose and properties of the gyroscope.
21. The principle of operation of the gyrocompass.
22. The principle of operation of a magnetic compass.
Connecting cables— a technological process for obtaining an electrical connection between two sections of cable with the restoration of all protective and insulating sheaths of the cable and screen braids at the junction.
Before connecting the cables, the insulation resistance is measured. For unshielded cables, for ease of measurement, one terminal of the megohmmeter is connected in turn to each core, and the second - to the remaining cores connected to each other. The insulation resistance of each shielded core is measured when connecting the leads to the core and its screen. , obtained as a result of measurements, must be no less than the standardized value established for a given cable brand.
Having measured the insulation resistance, they move on to establishing either the numbering of the cores, or the directions of laying, which are indicated by arrows on temporarily attached tags (Fig. 1).
Having completed the preparatory work, you can begin cutting the cables. The geometry of the cutting of the cable ends is modified in order to ensure the convenience of restoring the insulation of the cores and sheath, and for multi-core cables, also to obtain acceptable dimensions of the cable connection.
METHODOLOGICAL GUIDE TO PRACTICAL WORK: “OPERATION OF SPP COOLING SYSTEMS”
ON DISCIPLINE: " OPERATION OF POWER INSTALLATIONS AND SAFE WATCH KEEPING IN THE ENGINE ROOM»
COOLING SYSTEM OPERATION
Purpose of the cooling system:
- heat removal from the main engine;
- heat removal from auxiliary equipment;
- heat supply to the OS and other equipment (GD before start-up, VDG maintenance in “hot” reserve, etc.);
- intake and filtration of sea water;
- Blowing out Kingston boxes in the summer to prevent them from becoming clogged with jellyfish, algae, and dirt, and in the winter to remove ice;
- ensuring the operation of ice chests, etc.
One of the main parameters of periodic and pulsating currents is , which determines the number of periodic oscillations per full cycle and is the main characteristic of the SI system of units. The need for an accurate determination of frequency arises in various fields of scientific and practical activity; its determination is of particular importance in electrical engineering, radio electronics, telecommunications, etc.
To fix the frequency, frequency meters are used - these are special electrical measuring instruments used to fix the frequency of a periodic process or the harmonic components of the signal spectrum.
Classification of devices
Based on the measurement method, there are direct evaluation devices (analog) and comparison devices (heterodyne, electronic counting).
In order to determine the frequency of power supplies for radio devices, use:
- electromagnetic;
- electro- and ferrodynamic, using the method of comparison with a certain measuring scale;
- tuning fork instruments.
Such devices are characterized by narrow measurement limits, typically in the range of +-10% of one of the standard range of frequencies 25, 50, 60, 100, 150, 200, 300, 400, 430, 500, 800, 1000, 1500 and 2400 Hz, and operate at voltage ratings of 36, 110, 127, 220, 380 V.
For counting the maximum low frequencies(less than 5 Hz) use magnetoelectric devices complete with a stopwatch. To do this, by counting the number of oscillation periods over a certain time period, a complete measurement is carried out.
In addition, all frequency meters are conventionally divided into analog and digital devices. For the first option, the measured information is indicated by the standard “scale and pointer” method, and in the second - using a digital display.
According to their design, they are divided into:
- panel;
- portable;
- stationary.
T t or frequency fzap = 1/T.
The measured signal (let's assume a sinusoidal shape, Fig. 4.3, A) is supplied to the input A and through an adjustable attenuator AT arrives at the input of the shaper F a. At its output, a sequence of short pulses is formed with a repetition frequency equal to the measured frequency fx.
This sequence of pulses arrives at one of the inputs of the temporary selector BC. Its other input through the BA automation unit receives a sequence of rectangular control pulses, the duration of which is determined by the counting time interval Tcount
These pulses are formed from the voltage of the reference quartz oscillator CG by dividing its frequency in the frequency divider DF (Fig. 4.3, d). With division coefficient n, the value of the counting interval
The counts that have passed through the time selector N are counted by the pulse counter SCH. In the display block BI the measured frequency is determined
,
and the resulting value is displayed on the display block.
15. The operating principle of an electronic frequency meter when measuring a period
The discrete counting method is based on determining (counting) the number of cycles periodic signal for some countable set interval of time. This method also makes it possible to solve the inverse problem, i.e., measuring time intervals by determining the number of specially generated counting pulses in the measured time interval.
Let's say there is a time interval T, a sequence of short pulses with a repetition period t or frequency fzap = 1/T
These pulses are called filling pulses, and the frequency is called the filling frequency fzap. The number of pulses falling within the time interval is N.
The correspondence between these parameters can be written as an expression:
Signal from input B via attenuator A T fed to the shaper F B, where a sequence of pulses is formed where a sequence of pulses is formed with a period equal to the measured period Tx, and at the output of the automation block BA– control pulse duration Tx. In this case, the switch at the BA input is in the TB position.
By multiplying or dividing the frequency of the reference crystal oscillator KG in the time base BV a sequence of short counting pulses with a period is formed. These impulses are also called timestamps with period (frequency).
The N counting pulses that have passed through the time selector during the counting period are recalculated into the value of the measured period, and the result is displayed in the reading device. The value of the period of counting pulses (time stamps) can be set by the corresponding discrete switch.
If the switch at the input of the automation unit is set to position T B10, then in the process of measuring the period it can be carried out
averaging of a series of measured values, which is achieved by additionally dividing the frequency of the measured signal (or, accordingly, multiplying the measured period) by k once. Then, with the counted number of counting pulses N and the period t, the value of the measured period will be.
16. General information about instruments for studying the shape and spectrum of nonlinear signal distortions
Oscilloscope - This electronic device, having a channel y - vertical deflection, channel x - (time axis) horizontal deflection and an auxiliary channel z - beam illumination channel.
Spectrum Analyzer (AS) is a sensitive selective device designed to determine the frequency components of a signal, i.e. amplitude spectrum.
Modulation meter- a measuring device designed to determine the characteristics of a modulated radio signal - amplitude modulation coefficient and (or) frequency deviation.
17. Block diagram of a universal oscilloscope
Cathode ray tube(CRT) determines the operating principle of the device, and the parameters and application possibilities largely depend on its characteristics oscilloscope generally. Oscilloscopes mainly use CRTs with electrostatic beam control.
The principle of displaying the voltage waveform on the screen oscilloscope tube V general outline can be represented as follows.
The voltage being tested is a function of time, displayed in rectangular coordinates by a graph u = f (t ). Two pairs of CRT plates deflect the electron beam in two mutually perpendicular directions, which can be considered as coordinate axes. Therefore, to observe the voltage under study on the CRT screen, it is necessary that the beam be deflected along horizontal axis proportional to time, and according to vertical axis- proportional to the voltage under study (at each moment of time).
For this purpose, a sawtooth voltage is applied to the horizontal deflection plates, which causes the beam to move horizontally at a constant speed from left to right and quickly return back. The distance traveled by the beam along the horizontal axis is proportional to time.
The voltage under study is applied to the vertical deflection plates, and, therefore, the position of the beam at each moment of time uniquely corresponds to the value of the signal under study at that moment. During the action of the sawtooth voltage, the beam draws a curve of the signal under study. The image observed on the screen is called oscillogram .
Vertical channel Y, or signal channel, is designed to transmit the voltage of the source of the signal under study to the input of the vertical deflection plates of the CRT.
Horizontal channel X, or sweep channel, serves to create and transmit a voltage that causes horizontal movement of the beam, predominantly proportional to time.
Brightness control channel Z intended for transmission from the input Z to the control electrode of the CRT signals that modulate the brightness of the glow.
18. Purpose of channel Y of a universal oscilloscope, basic channel parameters
Input Device (Attenuator)– scales the signal to the level indicated in the technical specifications; the operator himself performs the scaling.
Pre-amplifier(Emitter follower):
1. Strengthens the signal
2. When the signal arrives, it generates a clock pulse
3. Matches the R output with the low impedance input of the delay line
Delay line delays the signal up to 140 μs, which ensures that an undistorted signal is received on the screen.
Vertical deflection amplifier (VDA) which amplifies the signal to a set value.
Channel Y is used to expand the signal under study in amplitude(designed to transmit the voltage of the source of the signal under study to the input of the vertically deflecting plates of the CRT.)
Many people leave all complex manipulations related to electricity and home wiring to professionals. Sometimes you need to check the resistance strength, direct or alternating voltage, as well as the number of complete cycles of current change, but it is not possible to call an electrician. In this case, it will come to the rescue useful device– multimeter. Despite the fact that this function is not the main one, many are interested in how to measure frequency with a multimeter.
Often a multimeter-frequency meter is needed for measurements in individual devices, such as a generator pulse block nutrition. Measuring the network value will only confirm the presence of an indicator of 50 Hz. A multimeter, the frequency of which in most models has a range of up to 30 Hz, is used only in everyday life; for production purposes, more complex devices are used, such as a high-frequency spark tester. It is necessary to familiarize yourself in detail not only with the design of the measuring apparatus, but also with the features of the device being measured in order to understand how to measure the frequency of the current with a multimeter.
Multimeter design
Tester with built-in frequency meter - excellent device for measurements, but there are a number alternative methods, which can be studied by familiarizing yourself with the structure of the device. The main composition of this device includes the functions of an ammeter, ohmmeter and voltmeter. Such a device is used when measuring constant and AC voltage, as well as resistance.
The most common model of this device is digital, since, unlike analogue, it allows for more accurate measurements. Classic design includes:
- Indicator. It is located at the top of the device and serves as a screen on which test data is displayed.
- Switch. Allows you to select indicator limits and values. There is a scale around the switch, which in most modern devices has five ranges. The first value indicates 200 ohms. If you set the switch to this scale, then it will not be possible to measure resistance greater than this indicator. The scale also includes indicators of switching between constant and alternating current, and the dialing icon.
- Probe sockets. Allows you to connect the device being measured to the tester. Most models have three connectors at the bottom.
For those who are interested in how to measure frequency with a multimeter, you need to pay attention to models with special functions. In addition to this indicator, the tester can measure inductance, temperature, and electrical capacitance. Availability additional functions significantly affects the cost, so not everyone can afford to purchase such a device for everyday use. A multimeter attachment can be an excellent solution. It allows you to measure the desired indicator using a device with a standard set of functions.
Frequency measurement
It is worth recalling that if you are interested in how to measure the frequency with a multimeter, it is first important to familiarize yourself with the features of the device that is to be tested. This is the only way to achieve the desired result with the most accurate indicators. Measuring frequency with a multimeter with special function is the most convenient, since in this case there is no need to use special attachments.
Such measurements take place in several stages:
- First of all, you need to check the meter for accuracy. It is known that the network frequency is 50 Hz. To determine the error in the tester's operation, you need to connect it to an outlet. An indicator different from 50 Hz will be the error of the measuring apparatus.
- Next, using measuring probes, you need to connect the tester to the device being measured. By first reading the instructions for using the tester, you can find out the voltage required for accurate testing. Having set the voltage indicator to the desired value, you can proceed directly to determining complete cycles of current change.
- After this, the frequency measurement by the tester will depend only on how the period of the alternating current changes.
Many are also interested in how to check the frequency with a multimeter using special attachments. Frequency meter - an attachment to a multimeter is an excellent alternative to expensive meters with many functions. Many testers with the function of determining current cycles have low sensitivity and therefore give inaccurate readings. The attachment is a complementary tool to the meter. It allows you to convert the received data into voltage.
In order for the current frequency measurement with a multimeter to have a minimum error, the frequency meter must be connected correctly. Switch type of work in measuring device must be adjusted so that the switch points to constant voltage. In this case, there is no need to rebuild the set-top box when connecting to a device with an input impedance exceeding 1 mOhm.
Measuring frequency with a tester can give different results, depending primarily on the accuracy of the device. Therefore, when choosing a verification method, it is necessary to decide how seriously the error of the device and/or attachment affects the performance.
Laboratory work No. 4
RESEARCH OF ELECTRONIC FREQUENCY METER
Purpose of the work: Study metrological characteristics, operating principles, block diagram, sources of errors of the electronic frequency meter. Learn to evaluate the errors in frequency measurement results caused by the errors of the frequency meter. Gain practical skills in working with a frequency meter.
Devices used: electronic frequency meter (ECF) Ch3-34A, low-frequency signal generator G3-109.
Brief theoretical information
Frequency measurement, frequency meters. Frequency measurements are the most accurate and fastest growing type of measurement. First, the unit of time (frequency) is the basic SI unit; secondly, the determination of the second is associated with the recalculation of events, and recalculation is the most accurate method of measurement; thirdly, increasing the accuracy of frequency measurements is necessary for applied use in telecommunications, navigation, and the space industry. Over the past 50 years, the total relative error of primary state standards based on cesium frequency references has decreased from ± 1 × 10 -10 to ± 1.5 × 10 -15, that is, the accuracy has increased by an order of magnitude every 10 years. No other type of measurement has such a significant increase, because an increase in accuracy by 2–3 times over 10 years is already considered an excellent indicator. The state primary standard and the state verification scheme for time and frequency measuring instruments can be divided into 3 segments:
working instruments for measuring frequency with an error of no more than ± 1×10 -7;
working frequency standards with an error of no more than ± 1×10 -12 ;
national and secondary frequency standards with an error of less than ± 1×10 -13.
Frequency meter- a measuring device for determining the frequency of a periodic process or the frequencies of the harmonic components of the signal spectrum.
Classification of frequency meters
By method measurements - instruments direct assessment (eg analogue) and comparison devices (eg resonant, heterodyne, electronic counting).
According to the physical meaning of the measured quantity - for measuring the frequency of sinusoidal oscillations (analog), measuring the frequencies of harmonic components (heterodyne, resonant, vibration) and measuring the frequency of discrete events (electronic counting, capacitor).
By design (design) - panel, portable and stationary.
According to the scope of application, frequency meters are included in two large classes of measuring instruments - electrical measuring instruments and radio measuring instruments. It should be noted that the boundary between these groups of devices is very transparent.
The group of electrical measuring instruments includes analog dial frequency meters of various systems, vibration meters, and also, in part, capacitor and electronic counting frequency meters. The group of radio measuring instruments includes resonant, heterodyne, capacitor and electronic frequency counters.
Resonant frequency meters
The operating principle of resonant frequency meters is based on comparing the frequency of the input signal with the natural resonant frequency of the tunable resonator. An oscillatory circuit, a section of a waveguide (cavity resonator) or a quarter-wave section of a line can be used as a resonator. The controlled signal is supplied to the resonator through the input circuits; from the resonator, the signal is fed through the detector to the indicator device (galvanometer). To increase sensitivity, some frequency counters use amplifiers. The operator adjusts the resonator according to the maximum indicator reading and limbo settings counts down the frequency. Their purpose is to configure, maintain, monitor the operation of transceiver devices, and measure the carrier frequency of modulated signals.
Capacitor frequency meters
Electronic capacitor frequency meters are used to measure frequencies in the range from 10 to 1000 Hz. The principle of such frequency meters is based on the alternating charging of capacitors from a battery with its subsequent discharge through a magnetoelectric mechanism. This process is carried out with a frequency equal to the measured frequency, since switching is carried out under the influence of the voltage being tested itself. During one cycle, a charge Q = CU will flow through the magnetoelectric mechanism, therefore, the average current flowing through the indicator will be equal to I_av = Qf_x = CUfx. Thus, the readings of the magnetoelectric ammeter turn out to be proportional to the measured frequency. The main reduced error of such frequency meters lies within 2-3%. Their purpose is to configure and maintain low-frequency equipment
Analog dial frequency meters
Analog frequency meters, according to the measuring mechanism used, are of electromagnetic, electrodynamic and magnetoelectric systems. Their operation is based on the use of a frequency-dependent circuit, the impedance module of which depends on the frequency. The measuring mechanism, as a rule, is a ratiometer, to one arm of which the measured signal is supplied through a frequency-independent circuit, and to the other through a frequency-dependent circuit; the rotor of the ratiometer with the arrow, as a result of the interaction of magnetic fluxes, is set to a position depending on the ratio of currents in the windings. There are analog frequency meters that operate on other principles. Used to control the power supply network.
Electronic frequency counters
The operating principle of electronic frequency counters (ECFs) is based on counting the number of pulses generated by input circuits from a periodic signal of arbitrary shape over a certain time interval. The measurement time interval is also set by counting pulses taken from the internal quartz oscillator of the ESC or from an external source (for example, a frequency standard). Thus, the ESC is a comparison device, the measurement accuracy of which depends on the accuracy of the reference frequency.
Frequency measurement principles
Among the digital devices of the frequency-time group, electronic counting frequency meters (hereinafter digital frequency meters - DF) are the most common, which is explained by their versatility, high metrological and operational characteristics.
The design of the central frequency unit is based on general principles that make it possible to implement a number of operating modes of the device for measuring several quantities. Functionally complete CNs allow you to measure the following quantities: frequency, period, ratio of two frequencies (sometimes expressed as a percentage), pulse duration or time interval specified by the user; a mode for counting events (pulses) and using a digital frequency frequency as a source of signals with known (calibrated) frequencies are also provided. Operating modes are set and selected by the position of a number of switches (mechanical or electronic) and other controls. In simpler versions, CNs are used to measure a smaller number of quantities (for example, one or two).
In any mode, part of the central frequency structure remains unchanged and the number of pulses is counted in it 
, proportional to the measured value. These pulses pass through the electronic key EC, which is in a closed state, to the SI pulse counter. The number code generated in the SI is sent to the digital readout device TsOU. The COU includes a multi-decade digital indicator with a moving decimal point and, as a rule, an indicator indicating units of measurement.
The time of the closed state of the EC, called the counting time T SF, is determined by the type of the measured quantity, and its specific value by a number of considerations, which will be discussed below.
The block diagram of the central frequency unit in this operating mode is shown in Fig. 1a.
Measured frequency voltage f x (Fig.1 b) is fed to the input of a forming device (FU), the purpose of which is to generate a signal of a standard shape with a fairly arbitrary shape of the input signal. Typically, the FU includes a limiting amplifier that provides a given amplitude of its output signal, and a shaper to ensure short rise and fall times of pulses at the FU output. The frequency of these pulses is equal to the frequency of the input signal (Fig. 1c). These pulses pass through the EC to the SI during the counting time T With , which is set by the reference frequency generator and the frequency divider. The HF frequency is stabilized by a quartz resonator. Necessary T With selected by the COUNTING TIME switch. Each time the device is started, one pulse appears at the DC output (Fig. 1c), under the influence of which the EC closes.
Number of pulses N x, transmitted to the SI, is determined by the approximate formula
and the value of the measured frequency
