FR2531782A1 - Method and device for the statistical measurement of transient perturbations occurring on an electrical line - Google Patents

Abstract

The method involves recording, during a predetermined sampling period, the highest detected level of perturbation and allocating this to one of a set of stepped classes of amplitude by incrementing a counter 411 corresponding to that class. The apparatus consists of an input stage 100, a range of high-speed comparators 210-270 controlling a self-locking switch 214, a series of EXCLUSIVE OR gates 310-370 selecting the highest level reached and delivering a signal authorising an increment in the associated counter 411.

Description

-1- The present invention relates to a method and a measuring device

  statistics of transient disturbances appearing on a power line

  brought to a reference level.

  "Electrical disturbance" means any unwanted signal appearing on an electrical power or information transmission line, or at a given point on an electrical circuit. These signals have an electromagnetic origin, and are conveyed or induced on the various connections or on alternative or continuous networks connected to sensitive equipment. These disturbances in particular have a harmful effect on computer systems for processing data in an industrial environment, or on automated machines managed by computer: in addition to a temporary or permanent alteration in the functioning of these devices,

  electrical disturbances can cause, in particular

  when they are of large amplitude, a destruction

  tion of sensitive circuits at the input of systems.

  It is therefore necessary to know the amplitude

  maximum that these disturbances can reach,

  i.e. the peak value (current or voltage) of the

  parasitic signal This maximum amplitude cannot

  not to be determined a priori, the disturbances,

  whether random or recurrent, having generated

  an unknown or not yet localized source.

  One of the aims of the invention is therefore to allow a statistical study of these disturbances, by recording the number of disturbances of defined level which have appeared, whatever their form (sinusoidal or

impulsive) and their polarity.

  2- The analysis of disturbances must be able to be carried out over a very long period, to allow the recording of disturbances of very low occurrence (sometimes less than once a month), which are those of maximum amplitude the most high and therefore those which present the most risks for the circuits. Another parameter that it is also interesting to analyze is the frequency of repetition of disturbances: for radio sets, this frequency may be characteristic of a level of annoyance according to the regulations concerning radio interference For analog systems with high constant of time, a repetition frequency

  too high can lead to an accumulation phenomenon.

  Finally, for logic systems, it increases the risk of default upon arrival in the phase of: ne; disturbance

and a control signal.

  By making it possible to understand the different parameters, the invention makes it possible to intervene effectively

  by shielding the sensitive system or sources of

  turbations (which it is possible to locate more easily

  or by changing the route of the line

  The impact of these various changes

  cations, hitherto carried out fairly empirically, can be known with precision thanks to the process

analysis of the invention.

  To this end, the invention consists in: determining

  ner, during a sampling period of predetermined duration, the disturbance having in absolute value the highest maximum amplitude; determine, from a series of successive classes of maximum amplitude values, the class corresponding to the maximum amplitude determined during the sampling period increment, during an acquisition period -3- consecutive to the period a digital counter corresponding to the value class thus determined.

  Preferably, during the trading period,

  tapping, only the pulses exceeding the reference level are retained for a duration greater than a predetermined value, that is to say that only the pulses having a sufficiently long duration are taken into account, therefore corresponding to a limitation towards the top of the bandwidth of the device Preferably also, during this sampling period, only the pulses whose

  the ratio of the amplitude to the reference level

  rence is greater than a predetermined value, which makes it possible to take into account only the truly significant disturbances taken into account from the reference level. The apparatus for implementing this method comprises a scale of comparators, each capable of emitting a detection signal when a transient disturbance appears on an electrical line, with an amplitude of a given level, specific to the comparator and understood between two lower and upper limits,

  associated with each comparator, storage means

  tion, able to keep, for the duration of a given sampling period, the corresponding detection signal, a series of counters, able to be incremented cumulatively, selectively by the comparators,

  means for addressing these counters, capable of

  verifying an authorization to increment the counter by the comparator having sent the detection signal corresponding to the highest level encountered during the sampling period, time control means capable of defining the sampling period and , at the end of the latter, incrementing the counter addressed by the addressing means by one step and resetting all of the storage means. Preferably, this device further comprises

  means, cooperating with the temporary control means

  to vary the length of the sample period

  tillonnage An analysis of disturbances in the

  time domain thus becomes possible.

  Other features and benefits of

  the invention appears 1 tront on reading the description

  detailed below, made with reference to the accompanying drawings, in which: FIG. 1 is a diagram showing an example of disturbance encountered, to illustrate the method of the invention, FIG. 2 is a block diagram of the apparatus for the

implementation of this process.

  In FIG. 1, there have been shown, as a function of time t, the variations of a reference signal V at voltage or current for example, around a reference level NR, which may be zero or substantially constant

  throughout the sampling period considered.

  Ideally, the signal V should have a straight

  line 10, but in reality it is affected by disturbances

  transients which give it the appearance of curve 20.

  It is the maximum amplitude of these disturbances, indi-

  fiercely above or below the reference level,

  that the process according to the invention seeks to study.

  For this purpose, we consider a period of exchange

  tillonnage Te, followed by a brief acquisition period T a The duration of the sampling period is for example chosen between 100 gs and 200 ms; the length of the vesting period (which must be the shortest -

  possible compared to that of the sample period-

  for no disturbance is taken into account during this acquisition period) is for example

in the range of 5 to 20 gs.

  During the period Te 1, only the perturbation having, in absolute value relative to the reference level, the highest peak value is retained: in the example of FIG. 1, this will be the perturbation referenced 21 for the first sampling period, and that referenced 22 for the second

  sample period shown.

  Having determined this disturbance, we

  lies, during the acquisition period Ta, a

  corresponding digital counter, among several inter-

  successive voltage valleys, to that corresponding

to the selected disturbance.

  We can for example choose a series of inter-

  voltage ranges from: 10 to 30 m V, 30 to 100 m V, 100 to 300 m V, 300 m V to 1 V, 1 to 3 V, 3 to 10 V and more than 10 V. This series of intervals (given only as an example) therefore makes it possible to perform a partition of

  the measuring range of the device in seven different classes

  which will allow a very fine analysis of the frequency of recurrence of disturbances as a function

of their amplitude.

  In this example and with reference to FIG. 1, if the disturbance 21 has an amplitude of + 4 V, the counter corresponding to the range 3 to 10 V will be incremented by one during the first acquisition period T a On the other hand, during the second acquisition period, if the disturbance 22 has an amplitude of 2 V, it will be the counter corresponding to

  the range 1 to 3 V which will be incremented.

2 531782

-6-

  Preferably, only the pulses will be retained.

  sions exceeding the reference level for a period greater than a predetermined value: it is thus possible to eliminate very short pulses, for example of width less than 20 ns, which corresponds in practice to a limitation of the higher bandwidth

of the device.

  Preferably also, it is possible to retain only the pulses whose ratio of the amplitude to

  reference level is greater than a pre-

  determined (for example greater than or equal to 6 d B).

  Figure 2 shows schematically the organization

  sation of the measuring device for implementing this method: the disturbed signal is applied to terminal E of an input stage 100 This stage attacks a series of comparators 210, 220, 270, corresponding to the different voltage intervals to study. Via doors 310, 320, 370, these comparators themselves attack counters 410, 420, 470 Preferably, these counters are identical in number to the comparators, each comparator

having an associated counter.

  A circuit 500 makes it possible to read and display the content of these counters; a 600 socket allows the

  connection to a recorder external to the device.

  A time control circuit 700 ensures the generation of clock signals and synchronization

of different tasks.

  The input stage 100 includes a resistance-capacity attenuator, making it possible to divide by 10, for example, the sensitivity of the device by the action of a selection switch 120 A first stage 130 of unity gain ensures the adaptation at low impedance of input E, which must be at high impedance (for example

  to allow the use of an oscilloscope probe).

  -7- Stage 130 is followed by a stage 140 for compensating for drifts, in particular temperature drifts: this stage requires at its output 51 to maintain a mean level of zero voltage (which does not prevent the transmission of disturbances, which are by definition transient), in order to maintain the maintenance of good accuracy of the levels of

weakest detection.

  The exit S of this stage 140 constitutes a

  first exit, which allows for example to attack directly

  the highest level detection comparators I (comparators 250, 260 and 270 corresponding

at levels above 1 V).

  To attack the comparators corresponding to the lowest levels (comparators 210, 220, 230 and 240, for levels between 10 m V and Vy), a second amplifier 150 is available, for example with a gain of the order of 50, thus defining a second output S

  All comparators have an identi

  that: they consist of a comparator 211 with a low threshold and a comparator 212 with a high threshold; outputs

  of these comparators are connected to an AND gate

  mandating at the output a self-locking flip-flop 214.

  This flip-flop keeps the signal in memory for the duration of the sampling period.

  detection of a corresponding level disturbance.

  Flip-flop 214 is reset to zero at the end of the sampling period by the time control circuit

700.

  The selection of the strongest level encountered is done by means of a series of OR EXCLUSIVE doors 310 to 370, connected in such a way that only one of the outputs of the OR EXCLUSIVE doors is at 1 among the seven outputs.

(o all are zero).

  8- The outputs of these doors attack counters 411 of which only one (or none) will be incremented, at the end of the sampling period, by the time control circuit 700, the presence of a signal at the output of a EXCLUSIVE OR gates constituting an authorization signal for incrementing the associated counter A bistable 412 is also provided at the output of each of the EXCLUSIVE gates, keeping in

  memory the state of the doors during the sampling period

  previous tillonnage These scales are reset to

  zero at the end of the next sampling period.

  There is thus obtained a time shift, of a duration substantially equal to a sampling period, of the information collected by the device, and which can be taken into account by a recorder connected to the socket 600 (it is indeed strong likely that a conventional recorder will not be able to take the information into account during the very short duration of the acquisition period, of the order of

a few microseconds).

  The circuit 500 includes a circuit 501 allows-

  both read the state of one of the counters selected by switch 502 and display the value thus obtained

by means of a display 503.

  Preferably, the duration of

  the sampling period, using a potentio-

  meter 701 of the time control circuit 700 We can for example continuously vary this

duration between 100 Us and 200 ms.

9-

Claims (12)

  1 Statistical measurement method of disturbances   transient states appearing on a power line brought to a reference level, characterized in that it consists, repeatedly, of: determining, during a sampling period of predetermined duration, the disturbance having an absolute value around the reference level, the highest maximum amplitude, determine, from a series of classes of maximum amplitude values, the class corresponding to the maximum amplitude determined during the sampling period, increment, during an acquisition period consecutive to the sampling period, a digital counter corresponding to the value class thus determined.   2 Method according to claim 1, charac-   terrified in that, during the sample period-   swimming, only the pulses exceeding the reference level are retained for a period greater than one predetermined value.   3 Method according to one of claims   1 and 2, characterized in that, during the sampling period, only the pulses are retained whose ratio of the amplitude to the reference level   is greater than a predetermined value.   4 Method according to one of claims   1 to 3, characterized in that the sample period-   swimming is chosen between 100 As and 200 ms.   Method according to one of the claims   1 to 4, characterized in that the acquisition period is between 5 and 20 gs -10- 6 Device for implementing the   method according to one of claims 1 to 5, character-   laughed at in that it comprises: a scale of comparators (210,270), each capable of emitting a detection signal when a transient disturbance appears on a power line,   with an amplitude of a given level, specific to the   parator and between two lower and upper limits,   associated with each comparator, memory means   station (214), capable of keeping, for the duration of a   given sampling period, the detection signal   corresponding counter, a series of counters (410 470), able to be incremented cumulatively, selectively by the comparators, means (310 370) for addressing these counters, able to issue an authorization to increment the counter by the comparator having emitted the signal   detection corresponding to the highest level encountered   very during the sampling period,   time control means (700) capable of   set the sampling period and, at the end of it, increment the counter addressed by the addressing means by one step and reset   all of the storage means.   7 Device according to claim 6, charac-   terized in that it further comprises means   storage diaries (412) capable of retaining, for the duration of the sampling period, the address of the   counter determined at the end of the sampling period previous lonnage.   8 Device according to one of claims   6 to 7, characterized in that it further comprises means (701), cooperating with the temporal control means -11- to vary the duration of the sampling period.   9 Device according to claims   6 to 8, characterized in that Oil further comprises compensating means (140), capable of maintaining at a mean zero level the signal applied to the scale of comparators.