Note: Descriptions are shown in the official language in which they were submitted.
BACKGROUND OF THE INVENTION
The present invention relates to a new and improved
method of detecting pre-magnetization of a magnetic circuit,
in particular for the detection of a current flow interlinked
with the magnetic circuit. The invention further relates to
apparatus for the performance of such method.
Magnetic circuits, generally in the form of highly
permeable and especially ferromagnetic cores, are suitable for
the detection of magnetic fields by virtue of the mayneti-
zation present in the magnetic circuit, which magnetization,
in the description to follow, for the purpose of differen-
tiating from a magnetization for producing required detection
signals, will be referred to as "pre-magnetization". When
such pre-magnetization corresponds to a current flow inter-
linked with the magnetic circuit, then there is produced
a current detection, especially, for instance, a null current
detection.
SUMMARY OF THE_INVENTION
It is a primary object of the present invention
to provide an improved method of, and apparatus for, rel:i.ably
detecting pre-magnetization and especially a corresponding
current flow with very li-ttle equipment expend:iture.
Another important object of the present invention
is to devise a novel method of, and apparatus for, detecting
a current flow in a highly efficient, reliable and simple
manner, by accomplishing an appropriate detection of
pre-magnetization of a magnetic circuit.
The inventive method for the detection of a pre-
magnetization of a magnetic circuit, especially for the
detection of a current flow interlinked with the magnetic
circuit, is manifested by the features that a temporal
cyclic magnetic flux change is produced by means of a
detection-current flow interlinked with the magnetic
circuit, and a detection signal is formed as a function
of pre-magnetization dependent-time intervals.
The apparatus for the performance of the method
is manifested by the features that there is provided at
least one detection current circuit interlinked with the
magnetic circuit as well as a supply source having a
cyclic current-or vol-tage time course. At least one thres-
hold value or limit switch is connected with the detection
current circuit, the threshold value switch being provided
with a subsequently arranged time interval detector.
The magnetic flux change produced in the maynetic
circuit, in addi-tion -to the pre-magnetiza-tion i..e. the
current flow which is to be detected, and the corresponding
current flow renders possible the determination of time
intervals, which directly or in the form of a suitable
-- 3
function derived from such time intervals -- e.g. a relation-
ship of time intervals -- characterize a pre-magnetization
statewhich is to be considered as static in relation to
the cyclic detection-magnetic flux change or a corresponding
current. Such time intervals and functions derived there-
from can be comparatively simply ascertained, with very
little equipment expenditure, with the aid of conventional
means available in analog or digital electronics, and in
comparison to the direct detection of a current- or voltage
amplitude, are manifested by great insensitivity to distur-
bance magnitudes and fluctuations in -the method- and circuit
parameters, such as temperature, manufacturing tolerances
of the electronic components and the like.
A particularly advantageous embodiment of the
method is manifested by the features that the detection
signal is formed as a function of time intervals which pass
between predetermined values during the cyclic magnetic
flux change of the detection-current flow or magnitudes
dependent upon such detection-current flow used for detec-
tion purposes. Especially for the detection of current flows
interlinked with the magnetic circuit there is provided a high
detection sensitivity because due to such a pre-magnetization-
current flow the magnetization characteristic curve (magne-tic
flux as a function of the detection-current flow) is shifted
in the direction of the current- or intensity axis and the
time intervals markedly change with the pre-magnetiza-tion-
current flow during throughpass of the magnetization
~$~
characteristic curve between predetermined values of the
current or a magnitude functionally lin~ed with the current.
Moreover, the use of interval determining current-limit
values, while advantageous in a number of aspects, nonethe-
less is not absolutely necessary. There also basically
come into consideration the possible use of other, for
instance~ relative boundary values, such as maxima, minima
or null throughpassage of the current or a suitable voltage.
In particular there can be advantageously introduced
current values of opposite sign for the interval determi- i~
nation, especially those of the same magnitude. This not
only provides for simple possibilities of circuit design,
but also the possibility of producing certain, usually
desired symmetry properties of the time intervals as a
function of the pre-magnetization-current flow. Particularly
simple conditions are realized when using the current null
throughpass for the interval determination.
Furthermore, the interval-determining current values
can be accommodated, in relation to a predetermined reference-
magnetization state, to certain exceptional points of the --
generally in any event non-linear -- magnetization character-
istic curve. Thus, there are obtained interval-de-termining
current values at the region of turning points of the
magnetization characteristic curve (magnetic flux as a function
of the detection-current flow) in a predetermined reference-
magnetization state of a particularly large sensitivi-ty
of the detection-time interval or a function of such time
intervals with regard to a change of the pre-magneti~ation
to be detected i.e. the Current to be detect~d. The afore-
o~ ~t~n
mentioned reference-ma~gcti~ær~ ~ state constitutes the
starting condition or null point of the detection. For tha
special function of a current-null detection there is thus
advantageously available the magnetization state o~ the
magnetic circuit without interlinked current flow, which
hereinafter will be simply referred to as "null magnetization"
with the corresponding "null characteristic curve". The
latter therefore constitutes the magnetization character-
istic curve only under the influence of the cyclic time
course of the detection-current flow, and in the following
discussion there will be assumed simplified cycles with
coincident starting- and end current values. In the case
of null symmetrical detection-current modulation or control
the null characteristic curves thus constitute commutation
`~ curves; in the case of a magnetic circuit with pronounced
saturation and modulation up to saturation such constitute
limit or threshold curves.
In the case of magnetic circuits of the last-
mentioned type there advantageously come into consideration
especially the use of interval-determining current values
in the saturation regions of the null characteristic curve
or another reference-magnetization characteristic curve,
especially the pairwise use of opposite saturation regions.
,~ , , i
.
The mere interval determination by current values in the
saturation region presupposes - as will be explained more
fully in detail hereinafter -- a not purely cons-tant speed
of change of the magnetic flux between the saturation-
boundary or limit points. Independent of predetermined
magnetic flux-time courses there also come into consider-
ation the use of interval-determining current values into
the saturation regions, however in combination with other
inter~al-determining current values during the course of
the cyclic throughpass o~ the magnetization characteristic
curve. Generally, the use of interval-determining current
in the saturation region affords the advantage of compara-
tively lower accuracy requirements with respect to the
current threshold or limit values, because the saturation
sections of the magnetization characteristic curve are
passed through at comparatively great speed in relation
to one and the same change in speed of the magnetic flux
and therefore only slightly come into consideration in the
determination of the total interval duration.
Furthermore, the interval-aetermining current
values can b~ placed with special advantage into the region
of the null throughpass of the magnetic flux in a reference-
magnetization characteristic curve wi-th hysteresis, i.e.
in the region of the coercive points of a conventional
ferromagnetic magnetization characteris-tic curve, for which
purpose -there especially is present slight sensitivity
- 7 --
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against non-systematic deviations of the change in speed
of the magnetic flux from the set reference values in
the different time intervals or characteristic curve
sections.
Moreover; it has been found that the interval-
; determination need not be absolutely carried out to both
sides of the entry of predetermined current values or
` corresponding magnitude values. Quite to the contrary,
it is possible, for instance, to basically work with
.1 10 partially fixedly predetermined temporal interval bound-
aries, approximately with a fixed cycle duration of the
detection-current flow in conjunction with magnetization-
dependent time interval boundaries within such cycle ~;
duration.
As the detection function (detection signal as
a function of magnetization-dependent time intervals) there
come into consideration preferred conditions owing to the
simple realizable and disturbance insensitivity, especially
the pulse duty factor of the cyclic time course of the
detection-current flow or a magnitude dependent therefrom.
While assuming that such time course is placed into a
binary state each time at the null throughpass there should
be understood in the present context as the "pulse du-ty
factor" the relationship of the time interval appearing at
a binary value or the sum of a number of such intervals
-- 8 --
within a cycle of the total cycle duration. Now if there
is accomplished a null-symmetrical binary opera~ion (swi-tching
between positive and negative values of the same magnitude),
then, the direct-current components which constitute a
pulse sequence (assumed to be stationary) directly provide
the pulse duty factor which can therefore be easily obtained
by low-pass filtering.
The time course of the interval-forming detection
magnitudes (detection-current flow or a magnitude dependent
therefrom) -- apart from the magnetization characteristic
curve representing the magnitude to be detected -- is
determined from the time course of the magnetic flux and
the properties of the detection current circuit interlinked
with the magnetic circuit. Belonging to the detection
current circuit is especially the current-voltage character-
istic curve of the current source which powers the detection
current circuit. This also is true ~or the time behavior
of such current source, however beyond such initially
there need only be fulfilled one precondition, in random
manner, which brings about the cyclic throughpass of the
magnetization characteristic curve. This can be basically
achieved by a periodically changing electromotive force,
by for instance current- or voltage-dependen-t switching
between different supply sources or between di~feren-t
current-voltage characteristic curves of a suppl~ source
or the like.
On the other hand, what is decisive for the
detection effect is the generation of a magnetic flux
change, for which purpose there is required in any event
a suitable current flow in the detection current circuit
interlinked with the magnetic circuit, and the determination
of a magnitude (detection magnitude) dependent upon the
magnetization state with a time course governed by the
magnetic flu~ change, during which there can be determined
the magnetization-dependent time intervals. To the extent
that the magnetization-dependency is given, there basically
come into consideration currents as well as voltages for
the detection magnitudes. Consequently, there are also
fixed the basic conditions for the supply of the detection
-~ current circuit to the extent that, on the one hand, the
magnetic flux change is to be generated by such supply, and,
on the other hand, however there is to be obtained from
the detection current circuit the magnetiza-tion-dependent
detection magnitude. If, for instance, there is used the
current as the detection magnitude, then the internal
resistance of the supply source must not be too large
(impressed voltage). The corresponding converse conditions
are also true for the use of the -terminal voltage of the
supply source or a detection winding of the magnetic circuit
as the detection magnitude. Eurthermore, the reduction
of the detection magnitude need not be carried out directly
in the detection current circuit. Quite to the contrary,
there is possible a decoupling of suitable de-tec-tion magni-
tudes, such as current or voltage also by means of special
current circuits.
-- 10 --
- The cyclic throughpass of the magnetization
- characteristic curve is advantageously obtained by reversing
the sign of the change in speed of the magnetic flux, e.g.
b~ reversing the polarity of the supply voltage. In the
interest of simple circuitry design there is thus advantage-
ously produced in the magnetic circuit a magnetic flux
having a time course which at least encompasses a pair of
intervals with change in speed of the magnetic flux of at
least approximately coincident magnitude and opposite sign.
Within one such interval of the same sign of the change in
speed of the magnetic flux it is then possible to work
especially with time sections of constant magnitude of such
change in speed. In consideration of the typical non-
linear course of the magnetization characteristic curve
of conventional highly permeable materials possessing
saturation, it can be advantageous to reduce the influence
of certain characteristic curve regions by more rapid
throughpassage i.e. with greater change in speed of the
magnetic flux, or conversely, -to increase the influence
of other regions by a slower throughpassage i.e. with
lower change in speed of the magnetic flux. For this
purpose there can be set within a cycle of the time course
of the change in speed of the magnetic flux at least two
intervals with different, preferably in each case time-
constant, magnitude and the same sign of the change of
speed of the magnetic flux.
-- 11 --
Basically, there can be introduced for the
variation of the speed change of the magnetic flux according
to magnitude and/or sign, for instance a constant time
frame. In particular, there is recommended, however,
resolution of these changes as a function of reaching at
least one predetermined value of the detection-current flow
or a magnitude dependent therefrom. The thus completely
or partially obtainable autonomy of the time-course modu-
lation or control provides a corresponding compensation of
disturbance magnitudes. Accordingly, the cyclic throughpass
of the magnetization characteristic curve thus can be
obtained in that there is accomplished a sign reversal of
the change in speed of the magnetic flux as a function of
reaching end or terminal values of opposite sign of the
detection-current flow or the magnetic flux, and such end
values for all of the values of the pre-magnetization to
be detected must be located in the saturation region of
the magnetization characteristic curve. In the case of
a hysteresis-magnetization characteristic curve, and
starting from the saturation region, there always then
will be throughpassed the boundary or limit curves, so
that the momentary effective pre-magnetization of preceding
magnetization states are without influence.
For the previously mentioned accentuation of
charac-teristic curve regions which are more productive for
the measurement effect -- in general regions which are
steeper wikh regard to the current flow axis -- there come
under consideration, while taking into account the advantage
- 12 -
sz'~
of an autonomous time control, a variation in the speed
of change of the magnetic flux as a function of an at
least approximate attainment of the value null of the
detection-current ~low. This reversing especially has the
advantage of a simple and exactly reproducible switching
criterion. Moreover, this reversal alone cannot bring
about any cyclic throughpass of the magnetization char-
acteristic curve and therefore should be combined with an
end value reversal, for instance one at both sides of the
saturation regions as previously explained. This also
is valid for a reversal at the turning points of the
magnetization characteristic curve, which, moreover~
produce a particularly great detection sensitivity with
regard to displacement of the magnetization characteristic
curve in the direction of the current flow axis. As simple
adjustable appro~imation of the turning points there
furthermore come into consideration, in the case of simple
type hysteresis loops, the coercive points, i.e. the null
throughpass of the magnetization characteristic curve. In
both of the last-mentioned embodiments there is to be
presupposed for the adjustment of the flow- or magnetic
flux values of the contemplated reversal of the change
in speed of the magnetic flux of a certain magnetization
state, for instance the previously above-mentioned null
magnetization.
A ~eneralization of the throughflow-dependent
control of the change in speed of the magnetic flux
leads to powering the detection current circuit by a
function generator with predetermined current-voltage
characteristic curve, which, in consideration of the
requirement of the cyclic throughpass of the magneti-
zation characteristic curve, must possess a hys-teresis-
like course with at least one positive and one negative
voltage branch. By virtue of the free design possibilities
of the current-voltage characteristic curve of such a
general supply voltage, which can be readily obtained
with conventional electronic circuits, there can be
realized optimum accommodations for different types of
detection functions and disturbance conditions.
The cyclic throughpassage of the magnetization
characteristic curve is obtained with a supply of the last-
mentioned type by advantageously switching between different
~unctions of the magnetic flux-speed change as a function
of reaching a predetermined value of the detection-current
flow or the magnetic flux, and specifically, advantageously
by switching between functions which in each case are free
of null positions and possess signs which are opposite to
one another. Since a switching of the last-mentioned type
constitutes a reversal of the travel direct:ion in -the
~ magnetization characteristic curve and thus generally
- also a direction reversal of the current flow-change,
there is here to be eliminated surging abou-t -the swi-tching
point by a one sided directed reversal or a one sided
direction dependency upon reaching the predekermined
switching point in the magnetization characteristic curve.
This can be particularly easily obtained in the end points
of the modulation and advantageously is avoid~d with the
last-mentioned mode of operation within the individual
function regions.
Particular advantages are generally afforded
by virtue of the more or less approximate impressing of a
voltage in a current path interlinked with the magnetic
circuit, advantageously in the detection current circuit
for determining the time change of the magnetic flux.
In the case of adequate low internal resistance of the
supply voltage in relation to a given inductance and a
llkewise effective resistance of the remaining current
path, this signifies a change in speed of the magnetic
flux of low current flow or current dependency. The
current changes which appear thus constitute a parti-
cularly sensitive measure for the pre-magnetization which
is to be detected, and specifically are even more pronounced
in the case of an at least timewise constant voltage or
magnetic flux-speed change, which moreover can be realized
with especially simple circuitry.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be better understood and
objects other ~han those set forth above, will become
apparent when consideration is given to the following
detailed description thereof. Such description makes
reference to the annexed drawings wherein:
Figure 1 is a principal circuit diagram of
an apparatus for the null current detection by means of
pre-magnetization of a magnetic circuit;
Figure 2a is a graph of the voltage-current
curve of a supply voltage for producing a detection
current flow with cyclic time course;
Figure 2b illustrates the linearly simplified
course of the magnetization characteristic curve of the
magnetic circuit (magne-tic flux as a function of the
detection current corresponding to the detection-current
`~ flow);
Figure 2c is a time diagram of the detecti.on
current corresponding to the supply characterist~c curve
(voltage-current curve of the supply source) according
to Figure 2a and the magnetization characteris-tic curve
according to Figure 2b;
- 16
Figure 3 is a circuit diagram of another embodi-
ment of an apparatus for the null current detection;
Figure 4a is a special supply characteristic
curve of an apparatus of the type shown in Figure 3;
Figure 4b illustrates a linearly simplified
magnetization characteristic curve having hysteresis for
the null current detection;
Figure 4c illustrates a first time course of
the detection current for null-symmetrical voltage of the
supply source;
",,~.
Figure 4d is a second time course of the
detection current for null-nonsymmetrical voltage of
the supply source;
'~
Figure 5a illustrates a further supply char-
acteristic curve with stepped voltage course;
Figure 5b illustrates a magnetization char-
acteristic curve corresponding to Figure 4b for de-termining
the detection current-time course;
Figure 5c illustrates the detection current-
time course resulting from the curves of Figures 5a and
5b; and
Figure 6 is a graph of the pulse duty ~actor
as the time-interval dependent detection signal as a
function of a current to be detected with regard to null
deviation.
DETAILED DESCRIPTION OF THE P~EFERRED EMBODIMENTS
. . _ . _ .
Describing now the drawings, the circuit of
Figure 1 will be seen to comprise a magnetic circuit 1
in the form of a ring core, by means of which there is
coupled or interlinked a current flow which is to be
monitored, for instance with regard to deviations from
the value null or with regard to exceeding a threshold or
limit value, for instance a current flow in the form o~
`~ the resultant flow through a number of conductors or lines
2 and 3. Furthermore, there is coupled with the magnetic
circuit 1 a winding 4 of a detection current circuit 5
composed, for instance, of a number of convolutions or
coils, the detection current circuit 5 being power supplied
by a suitable source 7 through the agency of a polarity
reversal switch 6. ~y appropriate actuation of the reversal
switch 6 by means of a control device 8 there is produced
in the detection-current circuit 5 a timewise or temporal
cyclically changing detection-current ~low which is
proportional to the current 1 in the detection current
circuit. In the simplest case where there ls used a direct~
current voltage source 7 the voltage u wh:ich is applied to
the winding 4 can be considered as constant in magnitude
with changing sign, provided that the voltage drop at
the internal resistance of the source 7 is sufficiently
small in relation to that at the winding 4. Furthermore,
i~ with sufficient inductance of the winding 4 with regard
to its ohmic resistance the voltage drop at the latter
can be considered as negligible, then there is directly
induced by the voltage source (terminal voltage) a
proportional change in speed of the magnetic flux in the
magnetic circuit. The cyclic time course of thismagnetic
flux change is obtained in the present simple situation
under discussion by the polarity reversal. For the
automatic triggering of suchreversal there come under
consideration different criteria, certain of which will
` be especially treated hereinafter.
:
By means of a current converter 9 having an
output signal Si (current signal) proportional to the
current i there is connected with the current circuit 5
a detection signal circuit 10 having at its input side
two parallelly connected threshold or limit value switches
11 and 12. According to the graphs of the momentary
output signals Sa and Sb plotted as a function of the
current signal Si and schematically shown in the blocks
of such threshold value switches, one is here concerned
with elements having binary, null-symmetrical output
signal, and ~urthermore, in the case of the switch 11 with
-- 19 --
a single switching threshold value Si = 0 ana in the case of
the switch 12 with two null-symmetrical threshold values
Si = Sil and Si = Si4. The output of -the switch 11 is
connected to a time interval detector 13 constructed
as a low-pass filter, and the ou~put signal Sa (plotte~
in the block symbol as a function of the fre~uency ~) is
a function of time intervals which are formed as a
function of the pre-magnetization of the magnetic circuit
1 and thus from the resultant pre~magnetization-current
flow of the conductors 2 and 3 during the cyclic time
course of the detection current i.
The detection-current flow need only sufficient-
ly distinguish itself from the pre-magnetization-curren~ flow
and the current to be detected merely by the cycle time
of its time course. Pre-magnetization i.e., currents
to be detected can change as a function of time, provided
only the change, within a cycle interval, is sufficiently
small in relation to the stroke change of the detection
current. Moreover, the cyclic time course of the detection
current and the magnetic flux change with constant duration
of the cycle intervals transforms into a periodic time
course, and there are valid appropriate conditions for
the period duration of the aforementioned time course.
Generally, for the sake oi simplicity there are employed
periodic time courses o~ the magnetic flux chanye, but
however there also come into considera-tion cyclic time
- 20 -
~,
eourses with variable eyele duration, for instanee
with ehanging speed of the pre-ma~netization which
fluetuates throughout wide regions or ranges. In the
deseription to follow the pre-magnetization will be
eonsidered to be eonstant during the eycle duration.
During the eyelic deteetion-magnetie flux ehange there
will be aeeordingly passed through a magnetization ehar-
aeteristie curve (magnetic flux as a funetion of the
deteetion-current flow or deteetion eurrent) which,
at least as concerns its position, is dependent upon the
pre-magnetization to be detected and thus upon the eurrent
flow to be detected. As the reference-pre-magnetization
there will be thus assumed in the following deseription
the already previously defined null magnetization.
In the example of Figure 1 the cycles of the
deteetion-magnetie flux change are brought about by
polarity reversal of the voltage u as a funetion of
reaching the predetermined current signal threshold
values Sil and Si4. Furthermore, the output of the
threshold value or limit switeh 12 is conneeted at an
input of the control device 8 which is reponsive -to the
ehanging polarity of Sb by-carrying out appropriate
opposite switching operations.
- 21 -
The power source 7 and the reversing switch 6
collectively form a detection-supply source having a
hysteresis-shaped voltage-current characteristic curve,
as indicated in full lines in Figure 2a. The detection-
supply source is to be considered as constituting a
function generator. The aforementioned characteristic
curve encompasses the inherently stable branches u = +U
and u = -U, at the ends of which there is carried out a
switching operation in the sense indicated by the arrows
and specifically at the current values il and i4 which
are associated with the current signal values Sil and Si4
according to Figure 1. Between these current threshold
or limit values there passes the magnetization character~
istic curve ~ as a function of i and assumed for the sake
of simplicity in Figure 2 to ke linear as well as without
hysteresis. The null characteristic curve is shown in
full lines, the magnetization characteristic curve which
is shifted owing to the pre-magnetization to be detected
is shown in broken lines. For the detection current
there thus results a curve course as a function of
time t as shown in Figure 2c~ and specifically, -the
full lines indicate the null characteristic curve and
the broken lines the pre magnetization to be detected.
Fur-thermore, in Figure 2c there is indicated the time
course of the output signal Sa of the threshold value
switch 11, i.e. a binary null-symmetrical signal Wi th
the period or c~cle dura-tion T and -thc null throughpasses
- 22 -
2~
in those of the detection current i. A comparison of
the time course indicated in full lines and in broken
lines for the null magnetization and the pre-magnetization
which is to be detected immedlately shows a clear change
of the pulse duty factor or switching relationship
determined by the time intervals between the null through-
passes, and from which there can be derived a corresponding
change of the direct-current component of Sa in the form of
the low-pass filtered signal Sa . The latter thus consti-
tutes the desired detection signal as a function of the
pre-magnetization-dependent time intervals.
In Figure 2a there is furthermore still shown
the possibility of working with other than current-
constant supply voltage functions. The chain-dot curve
section u is valid for a comparatively high internal
resistance of the supply source, whereas the curve sec-tion
uXx __ likewise shown in broken or chain-dot lines --
is valid for a source with corresponding non-linear
voltage-current characteristic curve. As to the first-
mentioned curve there results a non-constant time course
of also the supply voltage, so that, if desired, there
can be derived therefrom a detection signal, whereas a
drop of the supply voltage according to UX in a
correspondiny section of the null characteristLc curve
can result in a more pronounced effect oE the
premagnetization~dependent characteristic curve shifts.
- 23 -
What is here further to be mentioned is that a
supply source exhibiting in totality a hysteresis-like
current-voltage characteristic curve of the type shown
in Figure 2a can be basically realized by means of an
oscillator, for instance a relaxation oscillator or an
astable flip-flop circuit, if desired, while utilizing
suitable non-linear elements for influencing the individual
characteristic curve sections.
The circuitry of Figure 3 is not different
from the circuitry of Figure l as concerns the components
or elements l, 2, 3, 4, 5, 6, 8 and 12, whereas there is
used in place of the simple voltage source 7 a source 14
having a terminal voltage which can be controlled in
magnitude by means of a control input 14a and in place
of the hysteresis-free threshold value switch ll there
is employed a threshold value or limit switch 15 having
hysteresis-switching threshold or limit valu~s Si2 and
Si3 corresponding to the curves plotted in the blocks
for Sa as a function of Si. These changes and other
modifications which will be explained hereinafter allow
for special optimized detection processes. The control-
lable voltage source 14 in connection with a current-
dependent control circu:Lt and the polari-ty reversal
switch 6 already described in conjunction with the
circuitry of Figure 1 as well as its control device 8
- 24 -
assumes the function of a supply source with programmable
voltage-current characteristic curve and automatic,
especially current-dependent switching between a
characteristic curve section having positive and one
having negative voltage. The slope and curvature of
the characteristic curve sections can be additionally
influenced by an appropriate internal resistance of
the voltage source and non-linear circuit elements,
whereas in the embodiment under discussion there is
assumed a step-like composition of the characteristic
curve from sections each having current-independent,
yet programmable-variable voltage magnitudes. It should
be understood that such a function generator can be
realized by means of a supply source, if desired, by a
suitable oscillator or the like.
Additionally, the current-dependent control
device constitutes the detector part of the circuitry
where there are formed different types of detection
signals as a function of time intervals from the time
course of the detection current.
Starting from the circuit components which
coincide with those shown in Figure 1 and the already
mentioned threshold value or limit switch 15, according
to the showing of Figure 3 there is provided a logic
circuit 18 which logically couples the binary outpu-t
~ 25 -
- : ,
J~
signals of both ~hreshold value switches 15 and 12
by logical antivalence (Exclusive-OR) and delivers
an appropriate time interval-dependent detection
signal to an output l9. On the other hand, there can
be directly tapped-off at the outputs 16 and 17 other
types of likewise binary detection signals.
By means of -the switching threshold values
Si3 and Si4 the modulation range of the current i
during passage in the direction of increasing current
and by means of the switching threshold values Si2 and
Sil during passage in the direction of decreasing
current, is always subdivided in-to two sectionst and
there is associated with each section a binary output
signal combination, i.e. a two place binary number,
of the threshold value switches 12, 15. Accordingly,
the outputs of such switches lead to a logic circuit 22,
which is provided at the input side for each of the afore-
mentioned output signal combinations a parallel connected
group of AND-gates 22a, 22b, 22c and 22d. In Figure 3
there has only been illu~trated in each case one AND-gate
for each group. Upon the appearance of an output signal
combination, in other words when the current l increasingly
or decreasingly is located in a certain section of the
modulation range, there is thus always prepared in each
case an associated group of the AND-gates 22a to 22d
for the delivery of a yes-type ClltpUt signal, which
- 26 -
still depends upon in each case a further input 22al,
22bl, 22cl, 22dl. If each group of AWD-gates 22a, 22b,
22c, 22d encompasses for instance three gates, then
there are available the further inputs 22a2, 22a3;
22b2, 22b3; 22c2, and so forth. All of the inputs 22al,
22bl, 22cl, 22dl are collectively connected to a not
particularly referenced output of a coder 21, the Eurther
inputs 22a2, 22b2, and so forth as well as 22a3, 22b3
and so forth, are each connected to another associated
output of this coder, which, in turn, is controlled by
means of an analog-digital converter 20 by means of
the current signal Si. In total then for each output
signal combination Sa, Sb of the threshold valu~ or
limit switches 12, 15 there is prepared an associated
group of AND~gates 22a, 22b and so forth and by means
of the multiple outputs of the coder 21 controlled with
a coded binary current signal, the place number of which
corresponds to the output number of the coder and the
number of gates in the groups 22a, 22b and so forth.
Arranged following each of the last-mentioned groups
is, for instance, a respective programmable reader
storage 23a, 23b, 23c and 23d, having a corresponding
number of inputs of the associated, address-controlled
reader circuit (not here further shown). I'he outputs of
such storage-reader circuits are connected by means of
an appropriate multiplicity of OR-gates 24 with a
digital-analog converter 25, which, in turn, controls
- 27 -
by means of the input 14a the voltage source 14. Thus,
there can be basically automatically adjusted for each
value of the detection current a random selected value of
the supply voltage, i.e. the electromotive force in the
detection current circuit. This can be specifically
accomplished according to a predeterminable subdivision
into sections -- additionally, separately for increasing
and decreasing current -- of the current-modulation
range, each section having a clear correlation of voltage
and current and with automatic, current-dependent progressive
switching between the function sections as well as between
positive and negative voltage in the current end values.
Thus, there is shown the possibility of providing a
~eneral voltage-current-function genera-tor for the cyclic
throughpass of the magnetization characteristic curve,
and the freedom of fwnction programming within the current
sections is only limited by the steps- or place number
of the quantitizing binary system. Simpler and practical
realizations are correspondingly possible by suitable
oscillators of known construction, again, if desired,
in conjunction with predetermined internal resistance of
the source and/or non-linear elements for influencing
the characteristic curves.
In the description to Eollow -there will be given
the basic mode of operation while assuming comparatively
simple current-voltage characteristlc curves, for the
- 28 -
setting or adjustment of which there is only partially
utilized the possibilities of the circuitry of
Figure 3, as well as with llnear simpli~ied magnetization
characteristic curves, the latter however possessing
saturation and hysteresis.
With the mode of operation according to
Fiyures 4a and 4b there is initially again assumed a
simple voltage-current characteristic curve with current-
constant voltaye branches at ~U and -U as well as switching
between such at the values i = il and i = i4, respectively,
in the saturation regions of the full line null character-
istic curves of Figure 4b. Now there are set to deviate
however -- by means of the threshold value switch 15 of
Figure 3 -- the current threshold or limit values i2 and
i3, and specifically at the null throughpasses (coercive
points) of the null characteristic curve according to
Figure 4b. These limit or threshold values are employed
while utilizing the detection-current-time course according
to Figure 4c for the determination of pre-magnetization
dependent time intervals, and specifically, in the form
of the binary output singal Sa of the threshold value
switch 15 with its null throughpasses at i3 in the ascending
branch and at i2 in the descending branch of the mayne-ti-
zation characteristic curve, i.e. wlth positive and
negative supply voltage u.
- 29 -
~$'~C~I~
In Figure 4b there is further shown in broken
lines a magneti~ation characteristic curve which is shifted
by the pre-magnetization which is to be detected, and in
Figure 4c equally the corresponding time course of 1
and Sa. The change of the pulse duty factor of Sa in
the partial periods Tl and T2, here shown to be the same,
appears clearly by virtue of the pre-magnetization which
is to be detected. In the case of non-symmetrical supply
voltage -- indicated in Figure 4a by the larger negative
voltage -Ul -- there is changed according to the showing
of Figure 4d the relationship of the partial period or
cycle duration (T2 is shortened in contrast to T2),
however not the pulse duty factor in the partial periods
and therefore also not the total-pulse duty factor of
Sa i.e. the null point of the detection signal. This
voltage-independency of the null point constitutes a
particular advantage.
With the mode of operation according to Figures
5a to 5c there is carried out at the current threshold
or limit values i2 and i3 with decreasing and increasing
current a change in the magnitude of the supply voltage.
Thus, there is realized an additional non-linearity in
the time course of Sa and 1 as indicated in Figure 5c,
which however, as can be seen, has the effec-t of a more
pronounced change of the pulse duty factor of Sa in the
second partial period and thus in to-tal also the en-tire-
pulse duty factor with a displacement or shift of the
- 30 -
magnetization characteris-tic curve similar to Fiyure 4b.
This means a higher detection sensitivity.
Moreover, there is changed the duration of
the partial periods as a function of the pre-magneti-
zation change aecording to Figure 5e by ~ T1 and
T2, respectively, and spec.ifically in the opposite
sense, so that the relationship of the partial periods
between the opposite polarity eurrent pea]cs and which
can be easily determined can be employed as the detection
signal. Such then readily appears at the output ].6 of
the threshold value switch 12 in the form of the signal
Sb.
Furthermore, there ean be evaluated the pulse
duty factor in the individual partial periods, if the
binary detection signal -- deviating from Figure 4c and
Figure 5e -- is not only switched at the intermediate
eurrent values i2 and i3, rather also at the end or
terminal current values il and i4. If necessary, there
is then to be incorporated into the eireuit a reetifier
arrangement for obtaining the deteetion signal. The
deteetion signal appears for instance at the output 19
of the logic circuit 1~ in the embodiment of Figure 3.
As will be apparent from the showing of Figure 5c,
the changes in the opposite sense of the partial period
or cycle durations for a shift of the magnetization
characteristic curve are not completely of -the same
magnitude, so that there remains a change of the total
period or cycle duration, i.e. the frequency of the cyclic
throughpassage of the magnetization characteristic curve.
This effect is attributable to the finite slope of the
saturation branch of the magnetization characteristic
curve in relationship to the mean characteristic curve
branch and therefore actually is of lesser significance
for the practically available magnetic materials.
The detection method of the invention is
basically characterized by its low temperature sensitivity
of the null point and also by its low temperature depen-
dency of the detec-tion sensitivity at the region to both
sides of the null poin-t of the detection signal. To this
end Figure 6 illustrates measurement results of the
pulse duty factor n of Sa with a method according to
Fiyure 5a to Sc as a function of a pre-magnetization-
current flow ~ of the magnetic circuit, and specifically
for a temperature range between -~0C and ~100C. As
will be apparent both of the previously mentioned effec-ts
are very slight at the null point region. In contrast
thereto, the pronounced temperature dependency in the
practically non~interestiny marginal reyions A and B
- 32 -
.Z4~
shows that the strived for non-sensitivity is not
governed by the magnetic material, rather by the
circuitry and the detection technique.
- 32a-
