CZ279889B6 - Circuit arrangement of cable measuring instrument - Google Patents

Abstract

The wiring includes both an electrical input / output connector (BNC) and an optical transmitter (D1) and an optical detector (D2), with the optical transmitter (BNC) connector (D1) and detector (D2) being connected via a switch (Pr1, Pr2, Pr3) ) on the output of pulse source (PZ) and on the input of fast A / D comparator (KOMP), which are controlled by microprocessor unit (MJ). The microprocessor unit (MJ) receives data from a counter (NO) controlled by a pulse source (PZ) and a fast A / D comparator (KOMP). In addition, a keyboard (KL), a display (DISP), and a serial link (SL) are connected to the microprocessor unit (MJ), as well as a power and temperature control circuit (KONT). The battery pack (NZ) has a terminal (EXT) for connecting an external power supply. The wiring can be used for measuring cable parameters and faults. ŕ

Description

The invention relates to a cable meter connection for measuring a wide variety of cable types.

BACKGROUND OF THE INVENTION

A number of different connections are known for locating faults in cables. They are usually designed as single-purpose devices whose circuit connection is appropriate for the application. One circuit for fault location on the fiber-optic cable uses, for example, a time base block, amplifiers, a receiver / metering circuit, and an optical switch. In another wiring, to locate the transverse asymmetric location with respect to ground or other wiring for symmetrical cables, an AC voltage source, an indicator, impedance members, and variable resistors are used. In another known circuit for testing multi-conductor cables, a clock pulse generator is coupled to a counter and further to a multiplexer, with a demultiplexer at the input of the connector of the test cable.

It is also known to establish a location and magnitude of reflection from inhomogeneities in a line which includes both a broadband frequency modulated generator and a mixer which is connected to a measurement unit input via a tunable selective circuit.

A common disadvantage of all prior art connections is their low versatility resulting from a particular engagement for a particular purpose.

SUMMARY OF THE INVENTION

This prior art drawback eliminates the cable meter of the present invention, which comprises an electrical input / output connector and an optical transmitter and an optical detector. The connector is connected to a common terminal of a first switch whose first terminal is connected to a first output of a pulse source and whose second terminal is connected to a first analog input of a microprocessor unit via a first isolation amplifier. The second analog input of the microprocessor unit is connected via a second decoupling amplifier to a second terminal of a third switch, the common terminal of which is connected via a receiver to an optical detector and the first terminal of which is connected via a comparator to a sensing input of a fast A / D comparator. The first output of the fast A / D comparator is further connected both to the input of the pulse source and to the first terminal of the second switch, the second terminal of which is connected to a power source and whose common terminal is connected via an exciter to an optical transmitter. The first pulse source input is connected to the first control output of the microprocessor unit, the second control output of which is connected to the second pulse input. resources. The second pulse source output is connected to a counter input input, the reset input of which is connected to the third control output of the microprocessor unit. The clock input of the counter is connected to the output of the oscillator, while the control input of the counter is connected to the control output of the fast A / D comparator,

Whose two control inputs are connected to the third and fourth control outputs of the microprocessor unit. The data inputs of the microprocessor unit are connected to the data outputs of the counter. The microprocessor unit is further connected to a keyboard, a display and a serial line, the power and temperature control circuit being connected to a third analog input of the microprocessor unit, the power input of which is connected to a battery power supply having a terminal for connecting an external power supply.

An advantage of the present invention is that it allows the measurement of various types of cables, such as coaxial, twisted pair, optical fiber, etc. After setting the parameters measured on a known sample, virtually any cable can be measured, for example a conventional telephone line. enables measurement of optical cables.

Overview of the drawings

The attached drawing shows an exemplary connection of a cable meter according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

The cable meter according to the attached drawing comprises both an electrical input / output connector BNC and an optical transmitter D1 and an optical detector D2. The BNC connector is connected to a common terminal of the first switch U, the first terminal of which is connected to the first output of the pulse source PZ and the second terminal of which is connected via the first isolation amplifier 0Z1 to the first analog input of the microprocessor unit MJ. The second analog input of the microprocessor unit MJ is connected via the second isolation amplifier 0Z2 to the second terminal of the third switch Př3, the common output of which is connected via the receiver P to the optical detector D2 and whose first output is connected via comparator K to the A / D comparator . The first output of the fast A / D comparator KOMP is further connected both to the output of the pulse source PZ and to the first terminal of the second switch Př2, the second terminal of which is connected to the power source Z1 and whose common terminal is connected via an exciter B to the optical transmitter D1. The first input of the pulse source PZ is connected to the first control output START of the microprocessor unit MJ, whose second control output WIDTH is connected to the second input of the pulse source PZ. The second output of the pulse source PZ is connected to the setting input of counter C, whose reset input is connected to the third control output of the microprocessor unit MJ. The clock input of counter C is connected to the output of the OSC oscillator, while the control input START / STOP of counter C is connected to the control output of the fast A / D comparator KOMP, whose two control inputs are connected to the third and fourth control outputs of the A / D microprocessor unit. Data inputs of the microprocessor unit MJ are connected to the data outputs of the counter No. To the microprocessor unit MJ is connected both keyboard KL, display DISP and serial line SL, while control circuit KONT power and temperature is connected to the third analog input of microprocessor unit MJ, whose power input is connected to a NZ battery power supply provided with an EXT terminal to connect an external power supply.

-2GB 279889 B6

The device is based on the principle of reflectometer and acts as a radar. It is controlled by a microprocessor unit MJ, which created conditions for very easy operation and enabled to equip the device with a wide range of functions. The device allows the following types of measurements:

Measurement of coaxial cable lengths with an accuracy of + 1 m for the range of 10 to 500 m, for longer cables + 1 to 3%. The maximum measured length is 1,000 to 3,000 m depending on the cable quality, such as attenuation.

Detection of cable condition, such as short circuit, unconnected, and ohmic resistance of the cable.

Measurement of impedance differences at cable transitions, which makes it possible to detect, for example, a cable with incorrect impedance inserted into a segment, or a faulty terminating resistor - terminator.

Oscilloscopic measurements - if a very detailed detection of the waveform is required, the meter can be used in conjunction with an oscilloscope.

Optical fiber length measurement with accuracy of + 1 m for range 15 to 500 m, for longer cables + 1 to 3% with correct parameter setting. The maximum measured length is given by the quality of the connection, whose attenuation should not exceed 15 dB.

Measurement of optical fiber attenuation - determination of the basic parameter for optical measurements is especially important for testing optical connectors and other types of connections. The attenuation is measured in the range + 5 to - 40 dB with an accuracy of 0.1 dB.

The basic advantage of the measuring instrument is the fact that it allows to measure optical cables. Usually expensive and relatively large reflectometers are used for their measurement. The present invention operates as a so-called false reflectometer, which means that to work in this mode it is necessary to connect the fibers at the far end of the cable with a connector connector. This can be easily realized with most cables used in connection technology and computer networks and therefore measured without great cost. In addition, a single device is sufficient for measuring, unlike the usual two to three measuring units.

A significant advantage is that it allows orientation measurements for very short cables, metallic from 1 m or less, optical from 4 m.

The function of connecting the cable meter in each mode is described below.

When measuring the lengths of coaxial cables, the MJ microprocessor unit adjusts the KOMP fast comparator with its A / D outputs and the pulse width of the pulse source PZ by the WIDTH output. The MJ microprocessor unit generates a pulse by means of the PZ signal, which is pulled into the connected cable via the To switch and the connector and BNC. This pulse also starts with counter COMP. No. If the end of the measured cable is correctly terminated, no pulse is reflected into the instrument. But in the event of a cable failure, such as a short circuit, the transmitted pulse is reflected back into the device. Through the BNC connector and switch When this reflected pulse reaches the KOMP fast comparator,

-3GB 279889 B6 that evaluates it and stops counter # with a START / STOP signal. The MJ microprocessor unit evaluates data from counter # and displays the result of the measurement on the DISP display. The measurement result can be stored by the operator in the memory of the MJ microprocessor unit and later transferred via the SL serial line to the comp. with IBM PC.

When measuring fiber optic cable lengths, the MJ microprocessor unit sets the KOMP fast comparator with its A / D outputs and the pulse width of the PZ pulse source with the WIDTH output. The microprocessor unit MJ generates a pulse by means of a PZ signal, which is pulled to the optical transmitter D1 via the switch Př2 and the exciter B. It converts the electrical pulse into an optical pulse and sends it to the optical fiber. At the same time the counter No. is started. The measured fiber must be connected from the optical transmitter D1 to the optical detector D2. In the case of two fibers, the ends of the fibers shall be joined by an optical coupling.

The optical pulse, which has passed through the entire fiber, reaches the optical detector D2. Optical detector D2 converts this pulse into electrical pulse. Via the switch U and comparator K, this pulse reaches the fast comparator KOMP, which evaluates it and stops the counter No. with the START / STOP signal. The microprocessor unit MJ evaluates the data from the counter Č and displays the measurement result in the DISP display. The measurement result can be stored by the operator in the memory of the MJ microprocessor unit and later transferred via the SL serial line to the comp. with IBM PC.

When measuring the attenuation of the optical fibers, the current source Z1 via the switch V and the driver B supplies the optical transmitter D1. It transmits constant optical power to the connected optical fiber. Optical detector D2 converts this optical radiation into electrical voltage, which reaches operational amplifier 0Z2 via switch Př3. This adjusts the voltage and the microprocessor unit MJ receives the analog input. The MJ microprocessor unit evaluates the measurement result and displays DISP on the display. The measurement result can be stored by the operator in the memory of the MJ microprocessor unit and later transferred via the SL serial line to the comp. with IBM PC.

The ZERO function is used for attenuation measurement. The optical transmitter D1 and the optical detector D2 are connected via a calibration optical fiber (supplied with the apparatus). The microprocessor unit MJ sets zero value of optical power and stores it. The results of further measurements are derived from this value.

When measuring ohmic resistance using operational amplifier

0Z1, the measured cable connected to the BNC connector is connected by a switch

When the amplifier opamp is input, the microprocessor unit displays DISP. The measurement result can

0Z1. The operating voltage is evaluated and displayed to the operator to store the MJ microprocessor unit and later transfer it via the SL serial line to the comp. with IBM PC.

Most other cable meter functions are controlled by a program stored in the EPROM, which is part of the MJ microprocessor unit. The MJ microprocessor unit also performs calculations and various checks of the device function.

-4GB 279889 B6

Control is performed by a menu system from which the desired action is selected. The menus are displayed on the two-line LCD DISP. Possible numeric constants, which are rarely entered, are entered using the KL keypad, which is mainly used to select the relevant menu items.

The measurement results can be saved in the backed-up memory and after connection to a PC via the SL serial line, the data can be displayed on screen, printed on a printer, saved in a file and further processed if necessary.

The MJ microprocessor unit also controls power consumption, extending battery life. Using the KONT power and temperature control circuit, it also checks the battery charging and the thermal mode of the instrument ₍ to achieve the required measurement stability. Without external power supply, it is possible to work continuously for up to half an hour, which corresponds to about 100 measurements). 10 to 25 V power supply

Industrial applicability

The cable meter circuit according to the invention can be used in measuring technology, in particular for troubleshooting cable faults and measuring cable parameters.

Claims (1)

Cable meter connection comprising an electrical input / output connector (BNC) and an optical transmitter (D1) and an optical detector (D2), the connector (BNC) being connected to a common terminal of the first switch (Pri) whose the first terminal is connected to the first output of the pulse source (PZ) and the second terminal is connected via the first isolation amplifier (OZ1) to the first analog input of the microprocessor unit (MJ), the second analog input is connected to the second analog amplifier (0Z2) the output of the third switch (Pr3), the common output of which is connected via the receiver (P) to the optical detector (D2) and whose first output is connected via the comparator (K) to the sensing input of the fast A / D comparator (KOMP) connected to the output of the pulse source (PZ) and to the first outlet of the second switch (Př2), the second and the common output is connected via an exciter (B) to the optical transmitter (D1), while the first pulse source input (PZ) is connected to the first control output (START) of the microprocessor unit (MJ), the second control output (WIDTH) is connected to a second pulse source (PZ) input, the second output of which is connected to the counter input (Č), whose reset input is connected to the third control output (RESET) of the microprocessor unit (MJ), ) Is connected to the oscillator output (OSC), while the control input (START / STOP) of the counter ()) connects the control output of the fast A / D comparator (KOMP), whose two control inputs are connected to the third and fourth control output ( A / D) microprocessor unit (MJ), whose data inputs are connected to the data outputs of the counter (Č), while the microprocessor unit (MJ) is further connected to the keyboard e (KL), display (DISP) and serial line (SL), while the power and temperature control circuit (KONT) is connected to the third analog input of the microprocessor unit (MJ), whose power input is connected to a battery power supply (NZ) ), equipped with a terminal (EXT) for connecting an external power supply.