RU2233554C1 - Device for metering length of two-wire data transfer line - Google Patents

Abstract

FIELD: measurement technology; electrical means for metering parameters of two-wire data transfer lines.

SUBSTANCE: device has first and second test-signal input-output units connected to opposite ends of two-wire data transfer line under test; first test-signal input-output unit has microcomputer, pulse generator, line receiver, line transmitter, timer, multiplexer, flip-flop, matching resistors, and signal waveform recording unit; second test-data input-output unit has matching resistors, line transmitter, line receiver, and two pulse shapers.

EFFECT: simplified design, enlarged functional capabilities.

1 cl, 3 dwg

Description

The present invention relates to measuring devices using electrical means for measuring the length of a two-wire data line.

A device [1] is known for measuring the length of a two-wire data line using the scatterometry method based on sending probing pulses to a line and receiving reflected pulses. This device contains a probe pulse generator, a reflected pulse receiver, a microcomputer, an analog-to-digital converter, a memory unit, and two amplifiers. The output of the probe pulse generator is connected to the input of the reflected pulse receiver and is connected to the tested two-wire line. The microcomputer is connected to a probe pulse generator, a reflected pulse receiver, an analog-to-digital converter, a memory unit, and amplifiers.

The disadvantage of the device [1] is the small range of lengths of the measured two-wire lines. This is due to the fact that, on the one hand, a short probe pulse cannot cross a sufficiently long line and return back - it attenuates strongly and cannot be reliably recognized against the background of noise. On the other hand, with an increase in the duration of the probe pulse, the range of lengths of the measured two-wire lines expands, but quickly enters saturation. This is due to the fact that the duration of the probe pulse becomes comparable with the time of its propagation to the remote end of the line and vice versa. As a result, the obtained reflectograms become unsuitable for reliable recognition of the reflected pulse against the background of the probe due to their interference and the influence of other factors.

It was experimentally established that the reflectometry method for measuring the length of a standard telephone cable of the TPP-0.5 type (representing a set of twisted pairs of wires with a copper core diameter of 0.5 mm) does not allow working at distances exceeding 4 km, which is clearly insufficient for practical purposes, when a range of tens of kilometers is needed.

A device [2] for measuring the length of a two-wire data line containing the first and second blocks of receiving and receiving test signals connected to opposite sides of the tested two-wire data line, the first block of receiving and issuing test signals contains a microcomputer, a pulse generator, a first linear receiver , a timer, first and second termination resistors and a waveform registration unit comprising a memory unit, an analog-to-digital converter, and a first multiplexer whose data inputs are are the first and second inputs of the waveform registration block, the control input of the first multiplexer is connected to the input for enabling the analog-to-digital converter and is the third input of the waveform registration block, the fourth and fifth inputs of this block are connected to the signal inputs of the analog-to-digital converter with data inputs of the memory block, the outputs of which are a group of outputs of the waveform registration block, the output of the first multiplexer is connected to the synchronization input of the memory block with the start input of the analog-to-digital converter, the inputs of the first linear receiver are connected to the tested two-wire data line and are connected to the fourth and fifth inputs of the waveform registration unit and through the first and second terminating resistors to the zero potential bus, the output of the first linear receiver is connected with the first input port of the microcomputer, the first output port of which is connected to the first input of the waveform registration unit, the third input of which is connected to the second output port of the microcomputer An era, the group of input ports of which is connected to the group of outputs of the waveform registration unit, the output of the timer data is connected to the second input port of the microcomputer, the second block of reception and delivery of test signals contains the third and fourth terminating resistors, the first linear transmitter and the first pulse generator, the output of which is connected with the data input of the first linear transmitter, the outputs of which are connected to the tested two-wire data line and through the third and fourth terminating resistors to the zero bus potential of. The device [2] also contains two television receivers connected to the first and second blocks of reception and delivery of test signals.

The first and second blocks of reception and delivery of test signals of the device [2] are synchronized from the frame pulses coming from television receivers tuned to the same local television broadcasting station. This allows you to coordinate in time the times of issuing and receiving a test signal, represented by the voltage drop in the tested two-wire data line. To compensate for the difference in distance between each television receiver and television center, two series of measurements are carried out, which differ in the direction of transmission of the test signal. The results are averaged.

The disadvantage of the device [2] is the complexity. This disadvantage is associated with the use of two television receivers in the device. In addition, the functionality of the device is limited due to the ability to work only in the zone of reliable signal reception from the television center and in the absence of interruptions in broadcasting.

The purpose of the invention is to simplify the device and expand its functionality.

The goal is achieved in that in a device for measuring the length of a two-wire data transmission line containing the first and second blocks of receiving and receiving test signals connected to opposite sides of the tested two-wire data line, the first block of receiving and transmitting test signals contains a microcomputer, a pulse generator, the first a linear receiver, a timer, first and second termination resistors and a waveform registration unit comprising a memory unit, an analog-to-digital converter and a first multiplexer, data inputs of which are the first and second inputs of the waveform registration unit, the control input of the first multiplexer is connected to the input for enabling the analog-to-digital converter and is the third input of the waveform registration unit, the fourth and fifth inputs of this block are connected to the signal inputs of the analog-to-digital converter which is connected to the data inputs of the memory unit, the outputs of which are a group of outputs of the waveform registration unit, the output of the first multiplexer is connected to the synchronization input of the memory block and with the start input of the analog-to-digital converter, the inputs of the first linear receiver are connected to the tested two-wire data line and connected to the fourth and fifth inputs of the waveform registration unit and through the first and second terminating resistors to the zero potential bus, the output of the first linear the receiver is connected to the first input port of the microcomputer, the first output port of which is connected to the first input of the waveform registration unit, the third input of which is connected to the second output port ohm of the microcomputer, the group of input ports of which is connected to the group of outputs of the waveform registration unit, the timer data output is connected to the second input port of the microcomputer, the second test signal receiving-output unit contains the third and fourth terminating resistors, the first linear transmitter and the first pulse generator, the output of which connected to the data input of the first linear transmitter, the outputs of which are connected to the tested two-wire data line and through the third and fourth terminating resistors to to the zero potential bus, the first block of reception and delivery of test signals additionally contains a second linear transmitter, a second multiplexer, an element And a trigger, the control input of the second linear transmitter is connected to the first output of the pulse generator and to the third input port of the microcomputer, the second output of the pulse generator is connected to the input data of the second linear transmitter, with the first input of the And element and with the fourth input port of the microcomputer, the third output of the pulse generator is connected to the second input of the And element, the fourth and fifth outputs of the pulse generator are connected to the first and second data inputs of the second multiplexer, the control input of which is connected to the third output port of the microcomputer, and the output to the second input of the waveform registration unit, the third input of the And element is connected to the first input port of the microcomputer, a group of output the ports of which are connected to the group of timer inputs, the synchronization input of which is connected to the output of the AND element, and the output of the zero code flag is connected to the input of the trigger unit setting, the input of which the second is connected to the fourth output port of the microcomputer, the output of the trigger is connected to the fifth input port of the microcomputer and to an additional data input of the memory block, the additional output of which is connected to the sixth input port of the microcomputer, the second test signal receiving-output unit further comprises a second linear receiver and a second pulse generator the output of which is connected to the control input of the first linear transmitter, and the input to the input of the first pulse shaper and to the output of the second linear receiver Whose inputs are connected to outputs of the first linear transmitter.

Figure 1 presents the functional diagram of the device; figure 2 is a functional diagram of a timer; figure 3 - timing diagrams of the operation of the device.

A device for measuring the length of a two-wire data transmission line (Fig. 1) contains the first 1 and second 2 test signal reception-output blocks connected to opposite sides of the tested two-wire data transmission line 3, the first test signal reception-reception block 1 contains a microcomputer 4, a generator 5 pulses, the first line receiver 6, a timer 7, the first 8 and the second 9 terminating resistors and a waveform registration unit 10 containing a memory unit 11, an analog-to-digital converter 12 and a first multiplexer 13, data inputs They are the first 14 and second 15 inputs of the waveform registration unit 10, the control input of the first multiplexer 13 is connected to the operation enable input of the analog-to-digital converter 12 and is the third input 16 of the waveform registration unit 10, the fourth 17 and fifth 18 inputs of this block are connected to the signal inputs of the analog-to-digital converter 12, the outputs of which 19 are connected to the data inputs of the memory unit 11, the outputs of which are a group of 20 outputs of the waveform registration unit 10, the output of the first multiplexer 13 is connected with the synchronization input of the memory unit 11 and with the start input of the analog-to-digital converter 12, the inputs 21 and 22 of the first linear receiver 6 are connected to the tested two-wire data line 3 and are connected to the fourth 17 and fifth 18 inputs of the waveform registration unit 10 and through the first 8 and a second 9 terminating resistors - with a bus 23 of zero potential, the output of the first line receiver 6 is connected to the first input port 24 of the microcomputer 4, the first output port 25 of which is connected to the first input 14 of the waveform registration unit 10, the third the input 16 of which is connected to the second output port 26 of the microcomputer 4, the group 27 of the input ports of which is connected to the group of 20 outputs of the waveform registration unit 10, the output of the timer 7 data 28 is connected to the second input port 29 of the microcomputer 4, the second block 2 of receiving and issuing test signals contains the third 30 and fourth 31 terminating resistors, the first linear transmitter 32 and the first driver 33 of the pulse, the output of which is connected to the data input of the first linear transmitter 32, the outputs of which are connected to the tested two-wire line 3 and data transmission via the third and the fourth 30 and the terminating resistors 31 - 34 to the bus zero potential.

The first block 1 of the reception and delivery of test signals further comprises a second linear transmitter 35, a second multiplexer 36, an element And 37 and a trigger 38, the control input of the second linear transmitter 35 is connected to the first output 39 of the pulse generator 5 and to the third input port 40 of the microcomputer 4, the second the output 41 of the pulse generator 5 is connected to the data input of the second linear transmitter 35, with the first input of the And 37 element and with the fourth input port 42 of the microcomputer 4, the third output 43 of the pulse generator 5 is connected to the second input of the And 37 element, h the fourth 44 and fifth 45 outputs of the pulse generator 5 are connected to the first and second data inputs of the second multiplexer 36, the control input of which is connected to the third output port 46 of the microcomputer 4, and the output to the second input 15 of the waveform registration unit 10, the third input of AND 37 connected to the first input port 24 of the microcomputer 4, the group of 47 output ports 48-52 of which is connected to the group of inputs of the timer 7, the synchronization input 53 of which is connected to the output of the And 37 element, and the output 54 of the zero code flag is connected to the setup unit trigger input RA 38, the zero-setting input of which is connected to the fourth output port 55 of the microcomputer 4, the trigger output 38 is connected to the fifth input port 56 of the microcomputer 4 and with an additional data input 57 of the memory unit 11, the additional output 58 of which is connected to the sixth input port 59 of the microcomputer 4, the second block 2 receiving and issuing test signals further comprises a second line receiver 60 and a second pulse shaper 61, the output of which is connected to the control input of the first linear transmitter 32, and the input to the input of the first formate For 33 pulses and with the output of the second linear receiver 60, the inputs of which are connected to the outputs of the first linear transmitter 32.

The timer 7 (figure 2) contains a shift register 62 and a counter 63. The parallel outputs 64 of the data of the counter 63 are connected to the parallel inputs of the data of the shift register 62. The parallel outputs 65 of the data of the shift register 62 are connected to the parallel inputs of the data of the counter 63. The output port 52 of the microcomputer 4 connected to the serial data input of the shift register 62. The direction of the data shift in this register is shown by arrow 66. The input port 29 of the microcomputer 4 is connected to the serial data output of the shift register 62. The output port 49 the microcomputer 4 is connected to the input of the synchronization of the shift data of the register 62. The output port 51 of the microcomputer 4 is connected to the control input of the parallel data reception in the shift register 62 from the outputs 64 of the counter 63. The output port 50 of the microcomputer 4 is connected to the control input of the parallel data reception to the counter 63 from the outputs 65 shift register 62. The output port 48 of the microcomputer 4 is connected to the control input of setting the code "all units" in the counter 63. The output 54 of the timer 7 is connected to the output of the sign "all zeros" of the counter 63. Input 53 of the timer 7 is connected inen with the control input of the subtraction of the counter unit 63.

Figure 3 presents the timing diagrams of the operation of the device.

Diagrams 67 and 68 correspond to the signals at the outputs 41 and 39 of the pulse generator 5. Diagrams 69 and 70 display the signals at the inputs of the first 6 and second 60 line receivers. Diagrams 71 and 72 correspond to the signals at the outputs of the shapers 33 and 61. The part of diagram 69, highlighted by a circle 73, is shown in enlarged form as a fragment 74. In this fragment, diagram 75 displays the same signal as diagram 69. Diagram 76 corresponds to the signal on the output of the multiplexer 13. The part of the diagram 75, highlighted by a circle 77, in an enlarged view is shown as a fragment 78. On this fragment, the diagram 79 displays the same signal as the diagrams 75 and 69. The diagram 80 corresponds to the signal at the output of the multiplexer 13. Levels 81- 85 and 86- 90 voltages U1 and U2 between the wires of the tested line 3 on its opposite sides (at the inputs of the line receivers 6 and 60) correspond to high positive (81, 86), low positive (82, 87), zero (83, 88), low negative ( 84, 89) and high negative (85, 90) voltages.

The following describes the operation of the components of the device.

A high-precision 5-pulse generator is designed to provide synchronous operation of all components of the device. It contains five outputs: 39, 41, 43-45, on which periodic signals are generated, similar in shape to rectangular, with a duty cycle close to two. All signals generated by the generator 5 have fixed (unchanged in time) phase relationships. When measuring or counting the specified time intervals, the signal from the output 43 of the generator 5 passes through the element And 37 and enters the synchronization input 53 of the timer 7. The period of this signal sets the time quantum used by the device, and can be, for example, 5 ns.

The signals from the outputs 44 and 45 of the generator 5 determine two possible frequencies for recording digital samples of the analog signal coming from line 3 in the memory 11. The frequencies of the signals from the outputs 44 and 45 can be, for example, 50 kHz and 50 MHz. The choice of this or that frequency is made by the microcomputer 4 using the multiplexer 36 depending on the value of the control signal in its output port 46 of the microcomputer 4: with a zero control signal, the signal from the output of the generator 5 is transmitted to the output of the multiplexer 36, with a single signal from the output 45 of this generator .

The signals Y1 and Y2 from the outputs 41 and 39 of the generator 5 specify the operating modes of the linear transmitter 35. These signals have the same frequency (for example, equal to 10 Hz) and have a mutual phase shift equal to a quarter of the period (see figure 3, diagrams 67 and 68 ) The period t ₀ -t _{10 of the} signal Y1 determines the duration of the cycle of the device. With Y2 = 1, the transmitter 35 is turned on, with Y2 = 0 it is turned off, while its outputs are in a state with a high output impedance. The included transmitter 35 has a low output impedance and generates a high positive voltage U1 (level 81) between the direct and inverse outputs (between points 22 and 21) at Y1 = 1 and a high negative voltage (level 85) at Y1 = 0. The transmitter 32 operates similarly under the control of signals Y3 and Y4 from the outputs of the shapers 33 and 61 (see figure 3, diagrams 71 and 72); in the on state it forms a high positive (at Y3 = 1) or high negative (at Y3 = 0) voltage U2 (levels 86 and 90).

The durations of the fronts of the output signals of the linear transmitters 35 and 32 can be deliberately increased to some specified values (which are taken into account in the final calculations of the length of the line 3), and the shape of these signals is smoothed to reduce crosstalk induced on the adjacent wires of the cable in which the tested line is located 3 data transfers. Further, to simplify the presentation, it is assumed that the duration of the signal fronts at the outputs of the transmitters 35 and 32 when they switch from one active state to another is negligible.

Line receiver 6 performs the function of a comparator with respect to the signals received at its inputs. When U1> 0 (the voltage between its direct 22 and inverse 21 inputs is positive), the signal at the output of receiver 6 is equal to the log. 1; for U1 <0, this signal is equal to the log. 0. With U1 = 0, the output signal can be arbitrary (log.0 or 1). Receiver 60 operates similarly. The signal Y5 at its output is equal to the log. 1 for U2> 0 and log 0 for U2 <0.

Timer 7 operates in two modes.

In the first mode ("stopwatch"), it registers the time interval t ₀ -t ₇ (see Fig. 3) between the start of the device’s cycle (moment t _{0 of} issuing high positive voltage (level 81) to line 3) and the operation of receiver 6 ( moment t ₇ ) as a result of receiving a response signal (negative voltage) from the remote unit 2. The time interval t ₀ -t ₇ is not known in advance and depends, in particular, on the length of line 3 and its parameters. In the second mode ("alarm"), the timer counts a predetermined period of time from the moment t _{0 of the} beginning of the cycle to a certain moment t _С calculated by the microcomputer from the averaged results of previous experiments in which the "stopwatch" was used. The moment t _C is chosen between the moments t ₆ and t ₇ so that the plot of the diagram 79 (see Fig. 3) is most clearly traced near the moment t _{6 of} its initial deviation from the level 82. This, in turn, allows you to register the moment t ₆ ( possibly using approximation and interpolation) and use the obtained data to calculate the length of line 3.

The preparation of the timer 7 for operation in the first mode starts with the microcomputer 4 when it detects the transition of the signal Y2 arriving at the input port 40 from the state log.0 to the state log.1 (see Fig. 3, moment t ₈ ). Having detected this transition, the microcomputer 4 sets the group of output ports 47 to the state of log.0. Next, the microcomputer programmatically generates a pulse signal SET. To do this, he writes to port 48 first log. 1, and then log. 0. Under the influence of the pulse signal SET, the counter 63 of the timer 7 is set to the state "all units". Starting from the moment t ₁₀ (t ₀ ) of the start of the next cycle of the device operation, a pulse sequence from the output 43 of the generator 5 is received at the input of the timer 53. Each pulse reduces the contents of the counter 63 by one. The range of the account is chosen large enough so that the code in the counter 63 does not decrease to zero during the time t ₀ -t ₈ . At time t _{7, the} signal from the output of the line receiver 6 closes the And element 37, the operation of the counter 63 stops due to the lack of clock pulses at the input 53.

To read the code from the counter 63, the microcomputer 4 first writes this code to the register 62, and then sequentially pushes it to the input port 29. These operations are performed under the control of the corresponding program executed by the microcomputer 4. To transfer the data from the counter 63 to the register 62, the microcomputer programmatically generates pulse signal RD in the output port 51 (by writing to this port a sequence of signals: log.0 - log.1 - log.0). Subsequent data shifts in the register 62 occur under the action of software-generated pulse signals CLK in the output port 49. The output data of the DOUT timer 7 at each shift are sequentially read by the microcomputer 4 from the input port 29.

In the second mode, some code previously calculated by the microcomputer 4 is loaded into the counter 63 (the code is set in the "alarm"). Download starts after time t ₈ when the microcomputer 4 detects the transition of the signal Y2 arriving at input port 40 from state log.0 to state log.1. Counter loading takes place in two stages. At the first stage, the microcomputer 4 transmits the serial DIN code to the shift register 62 through the port 52, and then, at the second stage, it transfers the received parallel code from the register 62 to the counter 63.

The first step begins by setting the bits 48-51 to zero. At port 52, the first bit of code is set. Then, the pulse signal CLK is programmatically generated. The first DIN bit of the transmitted code is entered in the upper (according to the scheme) bit of register 62, the remaining data in this register is shifted down by one bit, and the DOUT bit is not read by the microcomputer and therefore is lost. Then, the second bit of code is entered into port 52, the pulse signal CLK is formed again, etc., until the shift register 62 is fully loaded. At the second stage, the pulse signal WR is generated in port 50 (log.0 - log.1 - log. 0), as a result, the parallel code from register 62 is rewritten to counter 63.

Starting from the moment t ₁₀ (t ₀ ) of the start of the next cycle of the device operation, a pulse sequence from the output 43 of the generator 5 is received at the timer input 53. Each pulse reduces the contents of the counter 63 by one. At some moment t _С (see Fig. 3, fragments 74, 78), a zero code is generated in the counter, in the next clock cycle the code is “all units”, then the count in the mode of subtracting units continues for some time. Upon detection in the counter 63 of a zero code at the output 54 of the timer 7, a log signal is generated. 1 for a duration of one clock cycle at input 53 (the alarm goes off). This signal is recorded by the trigger 38 and subsequently for some time accompanies the data accumulated in the memory block 11.

Block 10 recording the waveform in the presence of resolution (signal log.1 in the output port 26 of the microcomputer 4) constantly monitors the "recent history" of voltage between points 22 and 21 of the tested line 3. This allows you to get a kind of memory 11 in the memory block after removing the permission signal photo of the signal in the line by which it is possible to determine the moment t _{6 of the} beginning of the front of the response test signal received from block 2 (see Fig. 3, fragments 74 and 78).

The memory unit 11 operates on the principle of a pipeline. Under the action of the signal front CL at the synchronization input of this block, the next code from the outputs of the analog-to-digital converter 12 and the accompanying bit from the output of the trigger 38 are written to the beginning of the "conveyor". At the same time, as a result of data advancement along the “pipeline”, another code corresponding to the oldest history is sent to its outputs 20, 58. The length of the "conveyor" may be, for example, several hundred cells. In the absence of dynamics of the signal CL, the contents of the memory block 11 remains unchanged.

The analog-to-digital Converter 12 operates in the presence of a static signal of permission EN = 1. The start of the next conversion cycle occurs when a synchronization signal CL is received from the output of multiplexer 13.

The multiplexer 13 at C = 1 transmits to the output a signal from input 15 generated at the output 44 or 45 of the generator 5 (depending on the necessary degree of detail of the voltage diagram U1, see fragments 74 and 78 in FIG. 3). At C = 0, the multiplexer 13 transmits to the output a series of signals from input 14, which is generated by software when it is necessary to rewrite the contents of the memory unit 11 into a microcomputer 4 at a relatively slow pace.

The pulse shapers 33 and 61 are triggered on the positive edge of the signal Y5 from the output of the line receiver 60 and output pulse signals Y3 and Y4 in accordance with the timing diagrams 71 and 72 shown in Fig.3. The duration of the pulse signal Y3 (interval T ₄₂ = t ₄ -t ₂ ) is formed with high accuracy, for example, with a maximum deviation from the nominal duration by 2.5 not in the direction of increase or decrease. The duration of the pulse signal Y4 can be maintained with lower accuracy, since this duration is not taken into account when calculating the length of the tested line 3.

The following describes the operation of the device in general.

The length L of the checked line is calculated by the well-known formula

L = V _L × T _L ,

where V ₁ - the propagation speed of the signal in the data line;

T ₁ - the propagation time of the signal from the beginning to the end of the line (or in the opposite direction).

Moreover, V _L = c / k, where c is the speed of light in vacuum; k - the so-called "shortening coefficient", showing how many times the speed of light in vacuum exceeds the speed of propagation of the signal through the cable (for example, for cable type TPP-0.5 k = 1.52).

Thus, to calculate the line length, it is necessary to know the signal propagation time T _L from its beginning to the end. This time corresponds to the delay between the moment the test step signal is sent to the line and the moment it arrives on the opposite side of the line. In each cycle of the device’s operation, the test signal is first sent from block 1 to block 2, and then, after a precisely specified (previously known) time interval T ₄₂ = t ₄ -t ₂ (see Fig. 3), it returns from block 2 to block 1 As follows from the time diagrams shown in Fig. 3, the required time is represented by the interval T _L = T ₁₀ = t ₁ -t ₀ when the test step signal U1 is propagated from block 1 to block 2. The same time interval corresponds to the propagation of the step test signal U2 in the opposite direction when it is transferred from block 2 to block 1: T _L = T ₆₄ = t ₆ -t ₄ . The intervals T ₁₀ and T ₆₄ cannot be determined by direct measurements, since the information about the moment of formation of the test signal is "not known" to the receiving equipment located on the side of the line opposite to the one where the signal source is located. Therefore, indirect measurements are applied, which are carried out in two stages.

At the first stage, the microcomputer 4 performs a series of measurements of the duration of the time interval T ₇₀ = t ₇ -t ₀ . During measurements, timer 7 is used, which operates in the "stopwatch" mode. The measurement results are averaged to reduce the effect of line noise and other sources of error on them. At the same stage, the microcomputer 4 after each measurement looks through the shape of the response test signal during its rough registration (diagram 75) and calculates the timing t _{C of} the timer in the "alarm" mode, preparing for a more accurate registration of this signal (diagram 79). The moment t _C is chosen so that the inflection region of the diagram 75 (79) with more accurate registration falls approximately in the middle of the plurality of samples of the analog signal accumulated in the memory unit 11. Among the obtained values of t _C , the optimal one is selected.

At the second stage, a series of more accurate recordings of the inflection section of the diagram 79 shown in fragment 78 is carried out. The timer 7 operates in the "alarm" mode, which is triggered at the moment t _С , which precedes the registration completion. Each obtained diagram 79 is analyzed in order to calculate the moment t ₆ - the beginning of its inflection. The possibility of calculating the moment t _{6 is} based on the fact that the moment t _C and the step between the samples of the analog signal (horizontal distance between adjacent points or circles in diagram 79) are known, and the waveform can be traced by viewing the sequence of samples in the memory block 11. Received the results of determining the moment t ₆ are averaged. Thus, upon completion of the first and second measurement steps, the intervals T ₇₀ and T ₇₆ = T ₂₁ become known.

To calculate the desired interval T _{L the} following relation is used:

T ₇₀ = T ₁₀ + T ₂₁ + T ₄₂ + T ₆₄ + T ₇₆ = (T ₁₀ + T ₆₄ ) + (T ₂₁ + T ₇₆ ) + T ₄₂ = 2T ₆₄ + 2T ₇₆ + T ₄₂ ,

from which it follows that T _L = T ₆₄ = (T ₇₀ -2T ₇₆ T ₄₂ ) / 2. In the last ratio, the intervals T ₇₀ and T _{76 are} obtained as a result of measurements and calculations, and the interval T _{42 is} set in advance. The value of T _{L is} used by the microcomputer 4 to calculate the length L of the checked data transmission line 3 according to the above formula. The final result of measuring the length of the line is issued by the microcomputer 4 to an indicator (not shown in FIG. 1).

Depending on the mode of operation of the timer 7 selected by the microcomputer 4 ("stopwatch" or "alarm"), two variants of the operation cycle of the device are possible.

The first option is the cycle of the device

By the beginning of the next cycle of the device (in the period preceding the time t ₀ , see figure 3) in the timer 7 is loaded the code "all units". The signals log.0 from the output 41 of the generator 5 (Y1 = 0) and from the output of the line receiver 6 support the AND element 37 in the closed state, therefore, the clock signals from the output 43 of the generator 5 do not go to the input 53 of the timer 7. The trigger 38 is in the log state. 0 due to the previously generated positive pulse of zeroing in the output port 55 of the microcomputer 4. The linear transmitter 35 is maintained in the active state by the signal Y2 = 1 from the output 39 of the generator 5. At the outputs of the transmitter 35 a high negative voltage is generated (level 85), since its input d data there is a signal Y1 = 0.

In the output port 46 of the microcomputer 4, a log signal is generated. 0, therefore, the multiplexer 36 translates the output signal from the output 44 of the generator 5. This setting of the multiplexer 36 corresponds to a rough registration of the waveform (see diagram 75). In the output port 26 of the microcomputer 4, a log signal is generated. 1, therefore, the multiplexer 13 translates the output signal from the input 15, and the analog-to-digital Converter 12 is in the active state. Block 10 registering the waveform continuously accumulates in memory 11 a sequence of samples of the analog signal, to each of which a bit is added from the output of trigger 38. However, the data stream from outputs 20 and 58 of memory block 11 is not perceived by microcomputer 4 and is lost. In the output ports 25, 48-52 there are log signals. 0. The microcomputer 4 monitors the signal Y1 in the input port 42 and expects its transition from the state log.0 to the state log.1.

By the time the next cycle of the device starts (up to time t ₀ ), the linear transmitter 32 in block 2 is turned off by the signal Y4 = 0, a low negative voltage (level 89) is present at the inputs of the receiver 60, and a signal 0 is generated at the output of the receiver 60. A current flows in the line, limited by the ohmic resistance of the wires of line 3 and the resistance of the resistors 30 and 31 connected in series (with respect to the voltage source U1). The resistance of these resistors can be chosen sufficiently large (for example, equal to 5 kOhm).

At time t ₀ , a signal Y1 = 1 is formed at the output 41 of the generator 5, a high (level 81) positive voltage is outputted to the outputs of the transmitter 35, and a signal 1 is output 1. Element And 37 begins to transmit a high-frequency signal from the output 43 of the generator 5 to the input 53 of the synchronization of the timer 7, which starts the countdown. The voltage drop U1 begins to propagate along line 3. Microcomputer 4 detects and takes into account the fact of the beginning of the cycle (the transition of signal Y1 from state log.0 to state log.1) and begins to monitor the state of the signal in input port 24, waiting for its transition to state Log.0 when receiving a response test voltage drop from block 2.

At time t _1, the voltage drop reaches the opposite end of the line. This is manifested in the fact that the voltage at the inputs of the receiver 60 begins to increase approximately exponentially and tends to some low positive level 87, which is symmetrical to level 89 relative to zero level 88.

At time t ₂ , voltage diagram U2 crosses zero level 88, and a log signal is generated at the output of receiver 60. 1, shapers 33 and 61 pulses are started. The transmitter 32 goes into an active state and generates a high (level 86) positive voltage U2.

At time t _{3, the} transmitter 35 is turned off by the signal Y2 = 0, the voltage U1 begins to decrease exponentially to level 82. After some time, after the end of transient processes, the voltage U1 is fixed at this level. The state of the transmission line can again be regarded as static, in which the voltages and currents remain unchanged.

At time t _{4, the} signal Y3 at the output of the pulse former 33 goes into log.0 state, the transmitter 32 generates a high negative voltage U2 (level 90), which begins to propagate along line 3 towards block 1. At time t _5, the voltage drop reaches the opposite side lines. The moment t ₅ corresponds to the transition of the signal Y1 from the state log.1 to the state log.0, which, however, is not a significant event, since the transmitter 35 is turned off.

At time t ₇ , voltage diagram U1 crosses the zero level 83, a signal 0 is generated at the output of receiver 6, which closes the And 37 element, the arrival of clock pulses to the timer input 53 is stopped, and the time interval count code T ₇₀ is fixed in it. The microcomputer 4 detects the arrival of the signal log.0 in the input port 24 and sets the output signal 26 to the signal log.0, stopping the operation of the block 10 registration of the waveform. Next, the microcomputer 4 reads the timer (code corresponding to the time interval T ₇₀ ) and the contents of the memory block 11, which contains data conventionally shown by dots in diagram 75.

Due to the inertia of the microcomputer 4, a number of samples corresponding to the negative voltage U1 can be registered in the memory block 11 before it is suspended. These readings after reading them are recognized by the microcomputer 4 by the encoding of negative numbers, adopted in a particular model of the analog-to-digital converter. To advance data in the memory block 11, the microcomputer 4 programmatically generates control pulses in the output port 25, which pass through the multiplexer 13 and are fed to the synchronization input CL of this block. After each step of data advancement, the microcomputer reads the next word from the group of input ports 27. The data bits coming from the memory block 11 to the input port 59 are not taken into account by the microcomputer 4. Reading and processing of data obtained in this cycle are completed at time t ₈ .

At time t _8, microcomputer 4 detects the transition of the signal Y2 arriving at input port 40 from state log.0 to state log.1 and starts preparing for the beginning of the next cycle: sets timer 7 and trigger 38 to their initial states and outputs the necessary signals (described earlier), after which it goes on to wait for the start of a new cycle when the signal Y1 passes from the state log.0 to the state log.1. The signal Y2 = 1 puts the transmitter 35 in the active state, a high negative voltage is formed at its outputs (level 85). At time t _{9, the} transmitter 32 is turned off, the voltage U2 increases exponentially, and at time t ₁₀ (t ₀ ) it reaches a steady-state (static) level 89. Next, the described cycle is repeated.

The second option cycle of the device

By the beginning of the next cycle of the device’s operation (in the period preceding the moment t ₀ , see FIG. 3), its state corresponds to that described earlier (see the description of the initial state of the device when operating according to the first version of the cycle), taking into account two differences.

1. In timer 7, instead of the "all units" code, a code is loaded that causes the alarm to go off at time t _C. As already noted, the moment t _C is selected so that the history of the signal dynamics in the line recorded in the memory 11 maximum “visually” displays the portion of the initial inflection of the diagram 79.

2. The microcomputer 4 sets the signal log.1 in the output port 46, which sets the multiplexer 36 to transmit the signal from the output 45 of the generator 5 to the input 15 of the block 10. This signal has a higher frequency than the frequency of the signal at the output 44 of the generator 5 and provides more detailed registration of the waveform in line 3 (see diagram 79).

The operation of the device in the period t ₀ -t ₆ coincides with that described previously, however, in this case, the microcomputer monitors the signal in the input port 56 (it waits for the moment t _{C of} the "alarm"). At time t _C , a positive pulse is generated at the output 54 of timer 7 with a duration of one period of the clock signal at its input 53. This pulse sets trigger 38 to unity. The counter 63 of the timer 7 continues to work, but the counting results are not used in the future. The codes entered in the memory block 11 after the moment t _C are marked with a sign Z = 1, which is fed to its input 57. The microcomputer 4 detects the signal log.1 in the input port 56 and puts the output port 26 in the state log.0, stopping the operation of the block 10 registration of the waveform. During the time between the moment t _C and the moment the unit 10 was suspended, a series of samples marked with the sign Z = 1 manages to register in it (see fragment 78). After reading the contents of the memory block 11, the microcomputer 4 has enough information to recognize the moment t _{6 the} beginning of the deviation of the diagram 79 from the level 82.

At time t _{8, the} processing of data read from memory is completed. At time t _{8, the} microcomputer 4 detects the transition of the signal Y2 entering the input port 40 from the state log.0 to the state log.1 and starts preparing for the beginning of the next cycle. Next, the cycle of work is repeated.

Using the present invention allows to measure the length of two-wire data lines in a much wider range (compared to [1]) due to the transmission of rare or even one-time voltage drops (rather than short pulses that quickly decay even over short distances of about 4) km). At the same time, the useful signal propagates along the line against the background of a “static history” and in one direction, the reflected signals cannot get ahead of it and even catch it, so that a signal with a full shape of reduced amplitude and having a “blurry” front comes to the finish line. The measurement range can be further increased by increasing the level of the transmitted signal with a simultaneous controlled increase in the duration of its front. You can form the front in the form of a function graph

y = sin φt, where - π / 2≤φt≤π / 2, ω is a parameter that determines the steepness of the front.

An increase in the duration of the front and smoothing of its shape reduce the undesirable effect of the tested line on neighboring ones placed in the same cable. But even with a noticeable effect, interference is rare (or even once). Compared to the device [2], significant equipment savings were achieved (two television receivers were excluded) and functionality was expanded (work is possible in underground and other structures where there is no signal from the television center).

Sources of information

1. US patent No. 6097755.

2. RF patent No. 2187784 (prototype).

Claims (1)

A device for measuring the length of a two-wire data transmission line containing the first and second test signal reception-output blocks connected to opposite sides of the tested two-wire data transmission line, the first test signal reception and reception block contains a microcomputer, a pulse generator, a first linear receiver, a timer, a first and a second terminating resistors and a waveform registration unit comprising a memory unit, an analog-to-digital converter and a first multiplexer, the data inputs of which are first and the second inputs of the waveform registration unit, the control input of the first multiplexer is connected to the input for enabling the analog-to-digital converter and is the third input of the waveform registration unit, the fourth and fifth inputs of this block are connected to the signal inputs of the analog-digital converter, the outputs of which are connected to the inputs data of the memory block, the outputs of which are a group of outputs of the waveform registration block, the output of the first multiplexer is connected to the synchronization input of the memory block and to the input m start of the analog-to-digital converter, the inputs of the first linear receiver are connected to the tested two-wire data line and are connected to the fourth and fifth inputs of the waveform registration unit and through the first and second terminating resistors to the zero potential bus, the output of the first linear receiver is connected to the first input a microcomputer port, the first output port of which is connected to the first input of the waveform registration unit, the third input of which is connected to the second output port of the microcomputer, group the input ports of which are connected to the group of outputs of the waveform registration unit, the timer data output is connected to the second input port of the microcomputer, the second test signal reception-output unit contains the third and fourth termination resistors, the first linear transmitter and the first pulse generator, the output of which is connected to the data input the first linear transmitter, the outputs of which are connected to the tested two-wire data line and through the third and fourth terminating resistors to the bus of zero potential, characterized in that the first block of reception and delivery of test signals further comprises a second linear transmitter, a second multiplexer, an element And a trigger, the control input of the second linear transmitter is connected to the first output of the pulse generator and to the third input port of the microcomputer, the second output of the pulse generator is connected to the input data of the second linear transmitter, with the first input of the And element and with the fourth input port of the microcomputer, the third output of the pulse generator is connected to the second input of the And element, four the fifth and fifth outputs of the pulse generator are connected to the first and second data inputs of the second multiplexer, the control input of which is connected to the third output port of the microcomputer, and the output to the second input of the waveform registration unit, the third input of the AND element is connected to the first input port of the microcomputer, a group of output the ports of which are connected to the group of timer inputs, the synchronization input of which is connected to the output of the AND element, and the output of the zero code flag is connected to the installation input of the trigger unit, the input of which is zero connected to the fourth output port of the microcomputer, the output of the trigger is connected to the fifth input port of the microcomputer and to an additional data input of the memory block, the additional output of which is connected to the sixth input port of the microcomputer, the second test signal reception-output unit further comprises a second linear receiver and a second pulse shaper, the output of which is connected to the control input of the first linear transmitter, and the input to the input of the first pulse shaper and to the output of the second linear receiver, input rows are connected to the outputs of the first linear transmitter.

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