US20130187634A1 - Monitoring device and method for monitoring a line section using a monitoring device - Google Patents

Monitoring device and method for monitoring a line section using a monitoring device Download PDF

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Publication number
US20130187634A1
US20130187634A1 US13/743,123 US201313743123A US2013187634A1 US 20130187634 A1 US20130187634 A1 US 20130187634A1 US 201313743123 A US201313743123 A US 201313743123A US 2013187634 A1 US2013187634 A1 US 2013187634A1
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United States
Prior art keywords
current
input
monitoring device
differential amplifier
line section
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US13/743,123
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English (en)
Inventor
Stefan Albrecht
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TDK Micronas GmbH
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TDK Micronas GmbH
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Priority to US13/743,123 priority Critical patent/US20130187634A1/en
Assigned to MICRONAS GMBH reassignment MICRONAS GMBH ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: ALBRECHT, STEFAN
Publication of US20130187634A1 publication Critical patent/US20130187634A1/en
Priority to US14/509,803 priority patent/US9714962B2/en
Abandoned legal-status Critical Current

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
    • G01R19/04—Measuring peak values or amplitude or envelope of AC or of pulses
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R1/00—Details of instruments or arrangements of the types included in groups G01R5/00 - G01R13/00 and G01R31/00
    • G01R1/20—Modifications of basic electric elements for use in electric measuring instruments; Structural combinations of such elements with such instruments
    • G01R1/203—Resistors used for electric measuring, e.g. decade resistors standards, resistors for comparators, series resistors, shunts
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
    • G01R19/0092—Measuring current only
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R35/00—Testing or calibrating of apparatus covered by the other groups of this subclass
    • G01R35/005—Calibrating; Standards or reference devices, e.g. voltage or resistance standards, "golden" references
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/005—Testing of electric installations on transport means
    • G01R31/006—Testing of electric installations on transport means on road vehicles, e.g. automobiles or trucks

Definitions

  • the invention relates to a monitoring device and a method for monitoring a line section using a monitoring device.
  • the current of a ground line is monitored in that, in a first alternative, the current is ascertained from the measured voltage drop in the ground cable and the known resistance of the ground line based on Ohm's law.
  • the current in the ground cable is ascertained for an unknown resistance of the ground cable by means of a self-calibrating instrumentation amplifier from the voltage drop. Calibration is carried out using a precision resistor and a precision current source.
  • the voltage drop in the ground cable is conducted to an input of the instrumentation amplifier by means of an adjustable voltage divider. The voltage divider must likewise be calibrated.
  • the current in the ground cable is calculated from the comparison of the voltage drop at the precision resistor from the output of the instrumentation amplifier and the current source.
  • EP 0 206 488 A1 discloses measuring the voltage drop in a line through which current passes, in particular in a ground cable, by means of a Kelvin measurement circuit. The amplitude of the current in the line is determined from the voltage drop.
  • a constant current source is connected to the line by means of the Kelvin measurement circuit in order to calibrate a measurement instrument with a known current from the current source.
  • the amplitude of the current in the ground cable is ascertained from the measured voltage drop in the ground cable by means of the previously calibrated measurement instrument.
  • a monitoring device having a first line section with a first connection point and a second connection point spaced apart from the first connection point in the direction of the line, and having a control unit and a first current sensing unit, having a first current source, wherein the first current source is connected to the first connection point by a first connecting line and to the second connection point by a second connecting line and outputs a first current, having a first switch with a control input, wherein the first switch is inserted into the first connecting line and connects the first current source to the first connection point or disconnects it therefrom, having a first differential amplifier with a first input, a second input, and an output, wherein the first input is connected to the first connection point by a third connecting line and the second input is connected to the second connection point by a fourth connecting line, wherein the control unit is inserted between the output of the first differential amplifier and the control input of the first switch, wherein an actual current is passed through the first line section, and in a first state the first switch
  • a method for monitoring a first line section using a monitoring device wherein the first line section has a first connection point and a second connection point spaced apart from the first connection point in the direction of the line, wherein the monitoring device has a control unit and a first current sensing unit, and the first current sensing unit has a current source, wherein the first current source is connected to the first connection point by a first connecting line and to the second connection point by a second connecting line and outputs a first current, wherein a first switch with a control input is provided and the first switch is inserted into the first connecting line and the first switch connects the first current source to the first connection point or disconnects it therefrom, wherein a first differential amplifier with a first input, a second input, and an output is provided and the first input of the first differential amplifier is connected to the first connection point by a third connecting line and the second input of the first differential amplifier is connected to the second connection point by a fourth connecting line, and wherein the control unit is inserted between
  • An advantage of the monitoring device and the method for monitoring a first line section using a monitoring device is that during normal operation of a device, the current in a line of the device, in particular in a ground line of an electrical load, can be sensed without opening the line to be monitored, and in particular without interposing a cost-intensive shunt resistor and even without knowledge of the line resistance of the line section to be monitored. Moreover, standardization, i.e., calibration, of the voltage measurement instrument before a measurement is also rendered unnecessary. Investigations have shown that in the vast majority of cases, impressing the first current during ongoing operation causes only little or no impairment to the ongoing operation of the device. It is advantageous when the amplitude of the first current is in general chosen to be smaller than the actual current.
  • the method is also suitable for a low line resistance of the first line section of less than 0.1 ohms. Furthermore, by means of the precise measurement of low voltages, the method can in particular be used for monitoring lines with currents having a high amplitude, preferably above 100 mA, most preferably above 1 A.
  • the resistance of the line section can also be determined from a single measurement using a known current amplitude and the measured voltage if no actual current is impressed.
  • the accuracy of measurement of the resistance, especially of ground cables is completely unsatisfactory because of the very low line resistance, among other reasons.
  • the resistance of the line sections depends on the age of the line and environmental influences such as humidity and temperature, and in some cases is nonlinear in certain ranges of current amplitude. As a result, resistance measurements on lines through which no current is flowing provide only inaccurate results, especially when the measurements were performed a relatively long time ago.
  • the monitoring device achieves a significantly more accurate sensing of the current amplitude under real operating conditions.
  • the control unit can be configured to ascertain the amplitude of the actual current by means of the value of the voltage in the first state and by means of the value of the voltage in the second state and the amplitude of the first current.
  • the calculation of the amplitude of the actual current is carried out by means of the control unit from a measurement of the voltage in the first state and a measurement of the voltage in the second state and a measurement of the amplitude of the first current. In this way, the determination of the generally very small line resistance of the first line section, which has heretofore been used in the prior art and usually is very inaccurate, is avoided.
  • the actual current formula used is equal to the product of the first current times the voltage measured in the second state divided by the difference between the voltage measured in the first state and the voltage measured in the second state. In this way, the amplitude of the actual current can be ascertained without calculating the line resistance of the first line section.
  • the first current is impressed as a direct current in a first alternative and as an alternating current in a second alternative.
  • Investigations have shown that when the current is impressed as a direct current in a first alternative, no time-varying disruptions are impressed on the electrical network in the line and the device.
  • An embodiment according to the second alternative is especially advantageous when the actual current itself represents an alternating current and the impression of a first direct current is not desirable.
  • it is preferred for the frequency of the first current do be designed to be different from the frequency of the actual current.
  • an alternating current is fed into the first line section by means of the control unit in such a manner that the variation of the voltage is sensed by a lock-in principle, and by this means the amplitude of the actual current can be reliably sensed even for small changes in the voltages, preferably below 0.1 V, most preferably below 1 mV.
  • the first current source has a control input connected to the control unit.
  • the first current source can be switched both on and off by means of the control unit.
  • the amplitude of the first current, and if applicable the frequency of the first current in the embodiment of alternating current can be set, and in particular regulated as well.
  • the control input for regulating the first current source can be, among other things, the amplitude of the voltage difference between the measurements during the first and second states.
  • the first current sensing unit includes an ADC, wherein the ADC is connected between the output of the first differential amplifier and the control unit. It is an advantage that, as a result of the conversion of the analog voltage amplitudes into a digital count value, the data can be processed simply and reliably in the control unit, which preferably includes a processor.
  • the first current source can be connected to the first line section by means of the first switch and a second switch and a third switch and a fourth switch in the form of an H-bridge circuit.
  • An advantage of the H-bridge circuit is that the first current from the first current source can be fed into the first line section in both technical directions of current without further effort.
  • the first differential amplifier is connected to the first line section by means of an H-bridge circuit.
  • the two inputs of the differential amplifier can be connected to the first line section in such a way that the voltage difference between the two inputs is always present in the same direction and has the same sign.
  • a second line section with a second current sensing unit with a second differential amplifier wherein a second current is fed into the second line section.
  • the second line section can be directly adjacent to the first line section.
  • the second current sensing unit has circuit components corresponding to the first current sensing unit and that the circuit components are likewise connected in a corresponding manner. It is understood that in an especially advantageous refinement, the first current and the second current are essentially opposite and equal in amplitude.
  • control unit has a third differential amplifier, wherein a first input of the third differential amplifier is connected to the output of the first differential amplifier and a second input of the third differential amplifier is connected to the output of the second differential amplifier, and the first differential amplifier and second differential amplifier and third differential amplifier form a multi-stage amplifier unit.
  • a third line section is provided in addition to the first line section and the second line section.
  • the first line section and the second line section preferably are connected in series between a voltage source and a current source, for example between a battery and a ground potential.
  • At least one first current source with a first differential amplifier is associated with the first line section
  • at least one second current source with a second differential amplifier is associated with the second line section.
  • the third line section includes a battery with the battery's associated internal resistance and a line switch. The line switch is inserted between a predetermined point that is connected to a load, and labeled number 15 in a motor vehicle by way of example, and the positive pole of the battery.
  • the line switch connects or disconnects the positive pole of the battery to the particular section of the line that leads to the load.
  • a third adjustable current source is provided in parallel with the second current source. The control input of the third current source is connected to the control unit. By means of the third current source, the amplitude of the third current can be raised or lowered in such a manner that the summed value of the second and third currents is equal to, or preferably is approximately equal to, the value of the first current.
  • a first circuit arrangement comprises an analog-to-digital converter and a differential amplifier, and has a differential input connected to a first line section by a third H-bridge, and has an output connected to the control unit.
  • the third H-bridge comprises a ninth bridge switch and a tenth bridge switch.
  • a second circuit arrangement is provided in addition to the first circuit arrangement.
  • the second circuit arrangement comprises an analog-to-digital converter and a differential amplifier, and has a differential input connected to a second line section by a fourth H-bridge, and has an output connected to the control unit.
  • the fourth H-bridge comprises a thirteenth bridge switch, a fourteenth bridge switch, a fifteenth bridge switch, and a sixteenth bridge switch.
  • all bridge switches of the third H-bridge and in the fourth H-bridge are open.
  • all bridge switches of the first H-bridge and all bridge switches of the second H-bridge are open in the first mode. All control inputs are preferably connected to the control unit ST.
  • a third circuit arrangement is provided, wherein the third circuit arrangement includes a differential amplifier and an analog-to-digital converter.
  • each of the first to third current sources, and each of the first to third circuit arrangements as well, is connected to the associated line sections by an H-bridge, the result is great flexibility with regard to measurement of the voltage values at the first line section and at the second line section and in the combination of the individual measured voltage values.
  • a first input of the third circuit arrangement is connected to the ground potential
  • a second input of a third circuit arrangement is connected to the positive pole of the battery.
  • the first input and second input form a differential input.
  • the output of the third circuit arrangement is connected to the control unit.
  • the line switch When the line switch is closed, the actual current flows from the battery and causes a voltage change at the differential input of the third circuit arrangement.
  • the voltage change results from a comparison of the voltage present at the differential input of the third circuit arrangement when a line switch is open and when a line switch is closed.
  • the loading of the batteries which is to say the amplitude of the current drawn, can be determined.
  • the state of charge of the battery can be monitored from the measured voltage of the battery with a line switch open.
  • first H-bridge and the connected first current source can be aggregated into a first circuit block.
  • second H-bridge and the connected second current source can be aggregated into a second circuit block.
  • the third H-bridge and the connected first circuit arrangement can be aggregated into a first circuit section, and the fourth H-bridge and the connected second circuit arrangement can be aggregated into a second circuit section.
  • the first circuit block, second circuit block, first circuit section, and second circuit section can be aggregated into a first circuit unit.
  • the current in a single-phase generator or an electric motor can be monitored with such a circuit unit.
  • a second circuit unit and a third circuit unit are provided in addition to the first circuit unit.
  • the second circuit unit and the third circuit unit have a structure corresponding to that of the first circuit unit.
  • the first circuit unit is connected to a first generator phase
  • the second circuit unit is connected to a second generator phase
  • the third circuit unit is connected to a third generator phase. In this way, the current amplitudes in each of the three generator phases can be ascertained and monitored.
  • Phase currents are understood to mean the currents in the output leads of a generator. Such phase currents can easily reach current amplitudes of 10 A and more.
  • the monitoring device is especially suitable for ascertaining the state of charge of a battery.
  • the first connection point is the positive pole of the battery and the second connection point is the negative pole of the battery.
  • the monitoring device is especially suitable for monitoring the current in the ground lead of the battery in a motor vehicle.
  • the ground line from the battery to the vehicle is where especially high currents flow during the starting process, wherein it is advantageous to monitor the current amplitudes thereof for fault detection in a motor vehicle.
  • the current amplitude in the positive branch between the battery, in particular within the on-board power network of an automobile, and a load can be ascertained and monitored by means of the monitoring device.
  • Another especially advantageous application resides in the use of the monitoring device for in-situ calibration of unknown current amplitudes in a line section, wherein the variation of the current amplitudes in the line section advantageously spans at least a factor of ten. In this way, line sections that have completely different current amplitudes can be monitored in a simple and reliable way.
  • FIG. 1 shows a first embodiment of the monitoring device with a first current sensing unit
  • FIG. 2 shows a second embodiment of the monitoring device, wherein a first current is impressed as an alternating current by the first monitoring device;
  • FIG. 3 shows an equivalent circuit diagram of a monitoring device according to the embodiment from FIG. 1 ;
  • FIG. 4 a shows an equivalent circuit diagram of the monitoring device with a first current source embedded in a first H-bridge circuit in a first circuit state, and a second current source embedded in a second H-bridge circuit in a first circuit state;
  • FIG. 4 b shows an equivalent circuit diagram of the monitoring device from FIG. 4 a but the two H-bridge circuits are in a second circuit state;
  • FIG. 5 shows an equivalent circuit diagram of the monitoring unit with a multi-stage amplifier unit
  • FIG. 6 shows an equivalent circuit diagram of a monitoring device with a parallel circuit of a second current source with a third controllable current source
  • FIG. 7 shows a simplified equivalent circuit diagram of the embodiment from FIG. 6 ;
  • FIG. 8 shows another simplified equivalent circuit diagram with a plurality of monitoring devices.
  • the diagram in FIG. 1 shows a monitoring device UW with a first line section L 1 with a first connection point AS 1 and a second connection point AS 2 spaced apart from the first connection point AS 1 in the direction of the line.
  • the monitoring device UW has a control unit ST and a first current sensing unit STE 1 , as well as a first analog-to-digital converter ADC 1 , a first differential amplifier DIF 1 , and a first current source IQ 1 .
  • the first current source IQ 1 is connected to the first connection point AS 1 by a first connecting line ANL 1 , and to the second connection point AS 2 by the second connecting line ANL 2 .
  • the first current source IQ 1 outputs a first current I 1 .
  • a first switch S 1 is provided with a control input EST 1 , wherein the first switch S 1 is inserted into the first connecting line ANL 1 , and connects the first current source IQ 1 to the first connection point AS 1 or disconnects it therefrom.
  • the first circuit unit SE 1 has a first analog-to-digital converter ADC and a first differential amplifier DIF 1 .
  • the first differential amplifier DIF 1 has a first input, a second input, and an output, wherein the first input is implemented as an inverting input and is connected to the first connection point AS 1 by a third connecting line ANL 3 , and the second input is implemented as a non-inverting input and is connected to the second connection point AS 2 by a fourth connecting line ANL 4 .
  • the output of the differential amplifier is connected to an input of an analog-to-digital converter ADC.
  • the analog-to-digital converter ADC has an output connected to the control unit ST.
  • the first circuit unit SE 1 is inserted between the output of the first differential amplifier DIF 1 and the control input EST 1 of the switch S 1 .
  • the control unit ST is connected to the control input EST 1 of the first switch S 1 .
  • the first differential amplifier DIF 1 forms a first analog circuit block ER 1 .
  • the first line section L 1 is connected to the first connection point AS 1 at a reference voltage designed as ground potential.
  • a first actual current IST 1 flows in the first line section L 1 , which is to say that a device that is not shown is operated and draws current.
  • the first switch S 1 is closed and the first current I 1 is impressed on the first line section L 1 in addition to the actual current IST 1 .
  • a first voltage U 1 is present between the first input and second input of the first differential amplifier DIF 1 .
  • the first voltage U 1 is determined by the amplitude of the first actual current IST 1 and the amplitude of the first current I 1 and the non-negligible line resistance of the first line section L 1 .
  • the first switch S 1 is open and a second voltage U 2 determined exclusively by the first actual current IST 1 is present between the first input and second input of the first differential amplifier DIF 1 . It is a matter of course that the second voltage U 2 is different from the first voltage U 1 . If the first current I 1 has the same technical direction of current as the first actual current IST 1 , the first voltage U 1 is larger than the second voltage U 2 . Conversely, the second voltage U 2 is larger than the first voltage U 1 if the technical directions of the two currents are opposite. It is understood that the absolute value of the first voltage U 1 and the second voltage U 2 are always meant here. Furthermore, it should be noted that the amplitude of the first current I 1 is in general chosen to be smaller than the amplitude of the first actual current IST 1 .
  • the amplitude of the first actual current IST 1 is determined from the difference of the first voltage U 1 and the second voltage U 2 by means of the control unit ST. It can be appreciated that knowledge of the amplitude of the first current I 1 is needed to ascertain the first actual current IST 1 . In this way, a calculation or knowledge of the resistance of the first line section is avoided in an advantageous manner.
  • the representation in FIG. 2 shows a second embodiment of the monitoring device UW. Only the differences from the representation in FIG. 1 are explained below.
  • the first differential amplifier DIV 1 is integrated into a first analog circuit unit AFE.
  • the first analog circuit unit AFE 1 is connected to the first analog-to-digital converter ADC 1 by a first inverting signal line SIG 1 and a noninverting signal line SIG 2 .
  • a square-wave signal RSIG is present at the control input STE 1 of the first switch S 1 and the first analog circuit unit AFE 1 .
  • the first current source IQ 1 has a control input.
  • the control input of the first current source IQ 1 is connected to the control unit ST by means of a control line LIQ 1 .
  • the signal RSIG is produced by an external source that is not shown. In accordance with an alternative that is not shown, the signal RSIG can also be generated by means of the control unit ST.
  • the first analog circuit unit AFE 1 forms the first analog circuit block ER 1 .
  • the first switch S 1 is alternately closed and opened by means of the signal RSIG.
  • a first current I 1 is always impressed when the switch S 1 is closed.
  • the amplitude of the first current I 1 can be changed by means of the control unit SC.
  • FIG. 3 shows an equivalent circuit diagram of a monitoring device according to the embodiment shown in FIG. 1 or the embodiment shown in FIG. 2 . Only the differences from one of the preceding figures are explained below.
  • the first actual current IST 1 is impressed by a current source IQB on a series circuit having a first line resistance RL 1 and a second line resistance RL 2 and a third line resistance RL 3 .
  • a first voltage UA 1 drops across the first line resistance RL 1
  • a second voltage UA 2 drops across the second line resistance RL 2
  • a third voltage drops across the third line resistance RL 3 .
  • the third connecting line ANL 3 is represented by a fourth resistance RANL 3
  • the fourth connecting line ANL 4 is represented by a fifth resistance RANL 4 .
  • the input resistance of the first circuit block ER 1 is represented by means of a sixth resistance RDIFE. It should be noted that in the present case the input resistance is determined primarily by the input resistance of the first differential amplifier DIF 1 .
  • the output of the first analog circuit block ER 1 is represented by a first voltage source UQ 1 with an output resistance RA connected in series.
  • the first voltage source UQ 1 generates a first output voltage UA 1 , which is present at the differential input of the first analog-to-digital converter ADC 1 via the output resistance RA. In this way, it is evident that a monitoring device can be produced purely using analog circuit techniques even without an analog-to-digital converter.
  • FIG. 4 a shows a part of another embodiment of the monitoring circuit UW as a greatly simplified equivalent circuit diagram. Only the differences from the preceding figures are explained below.
  • the first current source IQ 1 is connected with a first H-bridge to the first line section L 1 .
  • the first line section L 1 includes a voltage source UQB as well as the line through which only current passes.
  • the circled numbers 30 and 31 label selected points of the cable routing in a motor vehicle, wherein the numbers 30 generally designate the positive input of the battery and 31 the return line from the negative pole of the battery to the ground cable in a motor vehicle.
  • the negative pole of the battery UQB is connected to the body by the ground cable.
  • the line resistance of the first line section L 1 and the internal resistance of the battery UQB are represented by a single equivalent resistance RLA.
  • the first H-bridge comprises a first bridge switch SH 1 , a second bridge switch SH 2 , a third bridge switch SH 3 , and a fourth bridge switch SH 4 .
  • the first bridge switch SH 1 and fourth bridge switch SH 4 are open, and the second bridge switch SH 2 and third bridge switch SH 3 are closed.
  • the first current source IQ 1 is connected to the first line section L 1 in such a way that the first current I 1 is impressed with a technical direction of current in the direction of the reference voltage or the ground potential.
  • a second current source IQ 2 is provided in addition to the first current source IQ 1 .
  • the second current source IQ 2 is connected with a second H-bridge to a second line section L 2 that is not shown directly.
  • the line resistance of the second line section L 2 is represented by an equivalent resistance RLB.
  • the second H-bridge comprises a fifth bridge switch SH 5 , a sixth bridge switch SH 6 , a seventh bridge switch SH 7 , and an eighth bridge switch SH 8 .
  • the fifth bridge switch SH 5 and eighth bridge switch SH 8 are closed, and the sixth bridge switch SH 6 and seventh bridge switch SH 7 are open.
  • the second current source IQ 2 is connected to the second line section L 2 in such a way that the second current I 2 is impressed with a technical direction of current opposite the direction of the first current I 1 .
  • the amplitude of the first current I 1 is especially advantageous for the amplitude of the first current I 1 to be essentially opposite and equal in amplitude to the second current I 2 .
  • the line network outside the monitoring device for example in the direction of a load that is not shown, is not loaded by the monitoring device, which is to say that no additional voltage drop is present in the line network outside the monitoring device.
  • a voltage source such as for example a battery UQB, can also be monitored in an especially simple and advantageous manner.
  • FIG. 4 b shows another preferred circuit embodiment of the first current source IQ 1 and the second current source IQ 2 . Only the differences from the embodiment in FIG. 4 b are explained below.
  • the first bridge switch SH 1 and fourth bridge switch SH 4 are closed, and the second bridge switch SH 2 and third bridge switch SH 3 are open.
  • the first current source IQ 1 is connected to the first line section L 1 in such a way that the first current I 1 is impressed with a technical direction of current opposite from the direction to the reference voltage or the ground potential.
  • the fifth bridge switch SH 5 and eighth bridge switch SH 8 are open, and the sixth bridge switch SH 6 and seventh bridge switch SH 7 are closed.
  • the second current source IQ 2 is connected to the second line section L 2 in such a way that a second current I 2 is impressed with a technical direction of current opposite the direction of the first current I 1 , which is to say that the second current I 2 is thus impressed in the direction of the reference voltage or the ground potential.
  • the amplitude of the first current I 1 to be made equal to the amplitude of the second current I 2 .
  • the line network outside the monitoring device is not loaded by the monitoring device, which is to say that no additional voltage drop is present in the line network outside the monitoring device.
  • first current source IQ 1 and the second current source IQ 2 can also be implemented.
  • the amplitudes of the first current I 1 and the second current 12 can be added together using two additional circuit implementations.
  • FIG. 5 shows another embodiment.
  • the embodiment shown has a multi-stage amplifier unit INST 1 , and for reasons of clarity represents only a part of the monitoring unit in a greatly simplified equivalent circuit diagram. Only the differences from the preceding figures are explained below.
  • the multi-stage amplifier unit INST 1 comprises the first differential amplifier DIF 1 , a second differential amplifier DIF 2 , and a third differential amplifier DIF 3 .
  • the first current I 1 is impressed on the first line section L 1 in addition to the actual current IST 1 that flows.
  • the second current I 2 is impressed on the second line section L 2 in addition to the actual current IST 1 that flows.
  • the first current I 1 is chosen to be opposite and equal in amplitude to the second current I 2 .
  • the voltage that drops across the line resistance of the second line section L 2 is present at a first input and a second input of the second differential amplifier DIF 2 .
  • the amplified voltage is output at an output of the second differential amplifier DIF 2 .
  • the output of the first differential amplifier DIF 1 is connected to a first input of the third differential amplifier DIF 3 and the output of the second differential amplifier DIF 2 is connected to a second input of the third differential amplifier DIF 3 .
  • the amplified voltage of the sum of the two output voltages of the first differential amplifier DIF 1 and the second differential amplifier DIF 2 is present at an output of the third differential amplifier DIF 3 .
  • the inputs of the first differential amplifier DIF 1 and the inputs of the second differential amplifier DIF 2 are connected to the relevant line sections such that the voltage drop of the first line section L 1 and the voltage drop of the second line section L 2 add together.
  • the first current source IQ 1 is shown as hard-wired to the first line section LI and the second current source IQ 2 is shown as hard-wired to the second line section L 2 .
  • One advantage is that with the connection of three differential amplifiers DIF 1 -DIF 3 as a multi-stage amplifier unit INST 1 , even very small voltages in the range below 10 mV can be reliably measured and evaluated. In this way, the actual current IST 1 can be ascertained in a simple, reliable, and analog way. From the analog output signals of the multi-stage amplifier unit INST 1 , with the impressed first current I 1 and second current I 2 and without the impressed first current I 1 and second current I 2 , the total resistance of the first line section L 1 and second line section L 2 , and thereby the amplitude of the first actual current IST 1 , can be determined by comparison of the voltage values.
  • the third differential amplifier DIF 3 by summation at the third differential amplifier DIF 3 , it is possible to ascertain the voltage drop due to the impressed first current I 1 and thus the line resistance. In a further step, the voltage drop due to the first actual current IST 1 , and thus the amplitude of the actual current, can be determined by forming the difference at the third differential amplifier DIF 3 .
  • FIG. 6 shows another, especially advantageous embodiment of the monitoring device UW.
  • the number 15 in a circle labels an additional selected point in the cable routing of a motor vehicle.
  • a third line section L 3 is provided in addition to the first line section L 1 and the second line section L 2 with the associated line resistances RLA and RLB.
  • the third line section L 3 includes the battery UQB, the inner resistance of the battery UQB, and a line switch SA with a line section, not shown in detail, between the point with the number 15 and the positive pole of the battery UQB.
  • All elements of the third line section L 3 are represented by a single equivalent resistance RLC.
  • the switch SA connects the positive pole of the battery UQB to the section of the line labeled with the number 15 or disconnects the positive pole therefrom.
  • a third adjustable current source IQ 3 is provided in parallel with the second current source IQ 2 .
  • the control input of the third current source IQ 3 is connected—not shown—to the control unit ST.
  • the amplitude of the third current I 3 can be raised or lowered in such a manner that the summed value of the two currents 12 and 13 exactly matches the value of the first current I 1 .
  • the first circuit arrangement DADC 1 comprises an analog-to-digital converter and a differential amplifier, and has a differential input connected to the first line section L 1 by a third H-bridge, and an output connected to the control unit ST. For reasons of clarity, the associated control inputs of all bridge switches are not shown.
  • the first line section L 1 is represented by the equivalent resistance RLA.
  • the third H-bridge comprises a ninth bridge switch SH 9 , a tenth bridge switch SH 10 , an eleventh bridge switch SH 11 , and a twelfth bridge switch SH 12 , wherein all bridge switches of the third H-bridge are open.
  • a second circuit arrangement DADC 2 is provided in addition to the first circuit arrangement DADC 1 .
  • the second circuit arrangement DADC 2 comprises an analog-to-digital converter and a differential amplifier, and has a differential input connected to a second line section L 2 by a fourth H-bridge, and an output connected to the control unit ST.
  • the line resistance of the second line section L 2 is represented by an equivalent resistance RLB.
  • the fourth H-bridge comprises a thirteenth bridge switch SH 13 , a fourteenth bridge switch SH 14 , a fifteenth bridge switch SH 15 , and a sixteenth bridge switch SH 16 . All bridge switches of the fourth H-bridge are open.
  • each of the current sources IQ 1 to IQ 3 and each of the circuit arrangements DADC 1 to DADC 3 as well, is connected to the associated line sections by an H-bridge, the result is great flexibility with regard to measurement of the voltage values at the first line section L 1 and the second line section L 2 and in the combination of the individual measured voltage values.
  • a first input of a third circuit arrangement DADC 3 is connected to the ground potential and a second input of a third circuit arrangement DADC 3 is connected to the positive pole of the battery QUB.
  • the first input and second input form a differential input.
  • the output of the third circuit arrangement DADC 3 is connected to the control unit ST.
  • the third circuit arrangement DADC 3 includes a differential amplifier that is not shown in detail and an analog-to-digital converter.
  • the switch SA When the switch SA is closed, the actual current IST 1 flows from UQB and causes a voltage change at the differential input of the third circuit arrangement.
  • the voltage change results from a comparison of the voltage present at the differential input of the third circuit arrangement DADC 3 with the switch SA open and with the switch SA closed.
  • the loading of the batteries which is to say the amplitude of the current drawn, can be determined.
  • the state of charge of the battery UQB can be monitored from the measured voltage of the battery with the switch SA open.
  • FIG. 7 shows a greatly simplified equivalent circuit diagram of a part of the monitoring device UW according to the embodiment shown in FIG. 6 . Only the differences from one of the preceding figures are explained below.
  • the first H-bridge and the connected first current source IQ 1 are aggregated into a first circuit block ISH 1 .
  • the second H-bridge and the connected second current source IQ 2 are aggregated into a second circuit block ISH 2 .
  • the third H-bridge and the connected first circuit arrangement DADC 1 are aggregated into a first circuit section SEH 1
  • the fourth H-bridge and the connected second circuit arrangement DADC 2 are aggregated into a second circuit section SEH 2 .
  • the first circuit block ISH 1 , second circuit block ISH 2 , first circuit section SEH 1 , and second circuit section SEH 2 are aggregated into a first circuit unit U 1 .
  • FIG. 8 shows another simplified equivalent circuit diagram of a monitoring device UW. Only the differences from one of the preceding figures are explained below.
  • the monitoring device UW has a second circuit unit U 2 and a third circuit unit U 3 .
  • the first circuit unit U 1 is connected to a first generator phase G 1
  • the second circuit unit U 2 is connected to a second generator phase G 2
  • the third circuit unit U 1 is connected to a third generator phase G 3 .
  • the current amplitudes in each of the three generator phases G 1 to G 3 can be ascertained and monitored.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Measurement Of Current Or Voltage (AREA)
  • Amplifiers (AREA)
US13/743,123 2012-01-16 2013-01-16 Monitoring device and method for monitoring a line section using a monitoring device Abandoned US20130187634A1 (en)

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US13/743,123 US20130187634A1 (en) 2012-01-16 2013-01-16 Monitoring device and method for monitoring a line section using a monitoring device
US14/509,803 US9714962B2 (en) 2012-01-16 2014-10-08 Monitoring device and method for monitoring a line section using a monitoring device

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DEDE102012000557.1 2012-01-16
DE102012000557A DE102012000557A1 (de) 2012-01-16 2012-01-16 Überwachungseinrichtung und Verfahren zur Überwachung eines Leitungsabschnittes mit einer Überwachungseinrichtung
US201261588971P 2012-01-20 2012-01-20
US13/743,123 US20130187634A1 (en) 2012-01-16 2013-01-16 Monitoring device and method for monitoring a line section using a monitoring device

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US20150022182A1 (en) 2015-01-22
CN103293369A (zh) 2013-09-11
US9714962B2 (en) 2017-07-25
EP2615472A3 (fr) 2015-09-02
CN103293369B (zh) 2016-04-27
EP2615472B1 (fr) 2016-11-23
DE102012000557A1 (de) 2013-07-18
EP2615472A2 (fr) 2013-07-17

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