DE2349110A1 - Digital position measuring system - with synchro resolver which utilises a digitised reference operating with a counter control system to provide angular position control - Google Patents

Abstract

An inductive position measurement system uses a sender synchro and a receiver synchro that have electrically coupled stator windings. The rotor of the sender synchro is coupled to a standard AC voltage generator. Depending upon the angular reference value, three measured voltages in the stator connections will result in an error voltage being generated. Comparison of the phase of the standard voltage with the error voltage in a comparator circuit results in an analogue error signal. Three discriminator circuits consisting of amplifiers and relays allow the three phase displaced signals from the stator windings to be digitised. The digitised reference is used to set counter circuits operating at a rate related to the standard input voltage frequency.

Description

BROWN, ROVFRI & CIE-AKTIENGESELLSCHAFT j j j / V ^

FZiAN K'H EIM BROWNBOVERi

Mp.no. 647/73 Mannheim, Sept. 26, 1973

PAT- Mn / Fl.

"Measuring device for a follow-up control system"

The invention relates to a measuring device for a Nach = j running control system with an actual value transmitter, a setpoint transmitter and ' an evaluation device for setting predefinable angular values on axes of mechanical pivoting or rotating devices such as rotatable antennas, machine tools, gyro platforms for navigation purposes, etc. known, inductive position measuring system is formed which has several induction coils, a part of the induction coils is acted upon by a normal alternating voltage of known magnitude and the other part of the induction coil at least a measuring alternating voltage which can be changed depending on the winding adjustment of an axis to be monitored is generated. !

Such devices are used in follow-up control systems. Fig. 1 shows the typical block diagram of a known one Follow-up control. Here is in the unit 1 an analog or digital control device A is provided in which the angle = setpoint S is entered. The actual angle value W is obtained via a

! Gearbox G detected, which is connected to the motor '' M via a tachometer T »The tachometer generator T delivers an actual speed value which is compared with the speed setpoint and; an amplifier V is supplied, which influences the motor M and stops at the required angle value. The actual angle value; W is fed here as the mechanical angle of rotation to the actual value measuring device I, the output signals of which are compared in the control device A with the desired angle values. The output signal

509814/0198

M mi'JjC i-V

of the control device A is proportional to the difference between the target angle value and the actual angle value, the amount of this difference representing the target speed value η -, -, and the polarity indicating the direction of travel for the motor M. A summing element 2 determines the difference between η _so -q and the actual speed value η taken from a tachometer generator 2. “α. and forwards this to an amplifier 'V, which controls the motor M. The gearbox G connects len motor M to the machine part, which Lageistv / ert (Drehv / incel) is to be detected. For the sake of simplicity, the control device is not shown in detail in FIG. The subject of the invention relates to the unit 1 in FIG. 1, into which the actual angle value w and in digital form the desired angle value S may arrive as input variables, and which emits a direct voltage proportional to the angle difference as an output variable for the control.

The object of the invention is to provide a device of the initially g ^ri ~! Type mentioned to provide, by means of which elsystemen a very accurate detection and evaluation of the measured values at Nachlaufre ^ is possible, the device should be fail-safe and the Sollwerfceingabe in digital form, e.g. via a process computer.

This is achieved in that the evaluation device used for comparing the actual and nominal value and for generating the difference value xjroportionfilen, control deviation voltage contains a circuit arrangement made up of electronic components, by means of which the control deviation voltage can be produced, evaluated and fed to the controller of the lag control system.

jVorteilhafterweise the device is configured so that the circuit arrangement includes a controllable rectifier least that every controllable rectifier is assigned a Meßwechnei.3pannung that at 3 / orhan which controllable rectifiers this offset by 2 \ J'5 ° can be switched on, that the switching on of the controllable rectifier from the difference

5098U / 01 SJ 8

ORIGINAL INiSPECTiD

2349 Π above

between setpoint and angle value. · against the phase of normal = AC voltage is dependent and that the resulting voltages can be summed at the output of the controllable rectifier.

According to an advantageous further development of the invention, the device must be designed so that the setpoint value is in digital form can be input into the evaluation device that an oscillator is provided, the frequency of which is an integral multiple of Normal AC voltage frequency is that the oscillator frequency in two counters connected one behind the other, it is divisible by an integer each, so that one of the counters is zero indicating output is led to ei-n zero coincidence element that the output of the zero coincidence element with one input of a AND gate is connected that the other input of the AND gate with a device for storing the digital Sollwer = tes is connected in a third counter that the setpoint number stored in the third counter has a further input by the oscillator oscillation can be continuously reduced to the value zero and that a value zero of this counter is one by one Normal alternating voltage, which is fed through a fundamental wave filter and fed to the inductive position measuring system, is shifted to the nominal value is present.

Further advantages and advantageous configurations can be found in the description and the subclaims.

Show it:

2a shows a known measuring and evaluation device with induk = tive position measuring systems,

2b shows a schematic representation of a first embodiment for an electronic evaluation device,

Fig. 2c shows a second embodiment of an electronic Aus = v.'erteeinrichtung,

Fig. 3 shows the circuit arrangement for the embodiment according to Figs. 2b and 2c,

- ti q .91 /. / ι ι

- 4 -

4 shows the operating diagrams according to the embodiment j Fig. 3,

! Fig. 5 shows the block diagram of the electronic evaluation = device, which the switches of the arrangement

3 controls and a normal alternating voltage = voltage for the transmitter of the inductive position measuring system supplies _r

6a to e are operating diagrams of the evaluation device,

7a shows a circuit arrangement for evaluating the measured values according to FIG. 6d,

Fig. 7b shows a circuit arrangement for evaluating the measurement = 'values according to FIG. 7e _f

8 shows an exemplary, schematically illustrated circuit arrangement for generating the normal change

self-voltage and to operate the switches,

9 shows an exemplary circuit arrangement with a! additional phase corrector,

^: Fig. IO the design of the phase corrector,

11 shows the mode of operation of the phase corrector according to FIG. 10 on the basis of operating diagrams.

Identical parts or parts with the same effect are provided with the same number.

ι In Fig. 2, an inductive position measuring system is shown, whose Sen = which is to be referred to below as transmitter synchro 3 and its receiver as receiver synchro 4. The Statorwick = Lungs of the transmitter synchro 3 and receiver synchro 4 are connected to one another in an electrically conductive manner via lines r, s, t. The The rotor 5 of the encoder synchro 3 is supplied with a normal alternating voltage u via a generator 7 via the line 8. The Ro = ! Tor 5 of the encoder synchro 3 detects the angle of rotation w of the object to be measured and, depending on the size of the angle of rotation, generates w meas =

5098U / 0198

234911Q

Voltages u, u ", u_ _f which are fed to the corresponding windings of the receiver-synchro 4 via the lines r, s, t, the position of the rotor 6 of the receiver-synchro 4 representing the position = soliwert ~ . Depending on the size of the nominal angle _{value, an error voltage u is generated by the three measurement voltages u, U 2} , u_, the phase of the normal alternating voltage u and the error voltage u "being compared with one another in an evaluation device 9 and one of the deviation of the two fourths proportional error voltage U _{pm is} formed.

The voltage supplied to the rotor 5 of the encoder synchro 3 is the size

u _o = u _o . sin (dt (1) and from this the stresses are formed

U ₁ = u _o »cos w (2)

U ₂ = u _o .cos (w-2tf / 3) (3)

U ₃ = u _q . cos (wf-2/1/3) (4)

In contrast to FIG. 1, the angle setpoint 6 ~ Ίη here shows, in the same way as the angle setpoint w, mechanically specified setpoint = angle C- 360. S / j \ , where Äj is the distance assigned to a synchro encoder rotor revolution. The voltage u_ on the rotor 6 of the receiver synchro 4 has the same size

Up = ^ «u _o ^ sIn (wC) (5)

To obtain a control DC voltage, this output voltage of the position detection system, usually also referred to as "error voltage ¹¹ ", is fed to an evaluation device 9, to which the normal AC voltage u is fed as a reference voltage from generator 7. If this evaluation device 9 detects both half-waves of the rotor voltage u _{p in the} correct phase , then is the mean value of the rectified fault voltage

J- (u

t) dt = I .U ₀ -sin (wr) (6)

5098 U / 0198

C .: · Ι r ι, 1.-Ν; ·. ■ χ. r _L ,

In all of these calculations an ideal behavior of all transfer elements was assumed, i.e. no amplitude damping and no phase rotations.

In Fig. 2b, the arrangement consisting of receiver synchro 4 and Auswerteinrich = device 9 for obtaining the rectified error voltage U of the unit 1 is replaced by three discriminators D ,, O ₀ , D_, each of which the mains voltage u, u ~, u-> V / earth supplied via lines r, s, t, to which the normal alternating voltage u from generator 7 and the angle setpoint are also supplied via line 8. The outputs of the discriminators are fed to a summing element 11, at its output the rectified fault voltage U _p appears.

In Fig. 2c, an embodiment is shown in which a : Input device Io for all three discriminators D, D ", D_ is provided, which an angular setpoint iT 'from the entered Setpoint S forms and supplies all three and also forms a normal = alternating voltage u, which forms the rotor 5 of the encoder-synchro 3 is fed.

For FIGS. 2b and 2c it applies that the output voltages of the discriminators D, D ₂ , D_ each wind a summing element 11, the switch-on limits of these discriminators being offset from one another by 2 # / 3 = 120 ° and by a total of the setpoint angle ff " _{are shifted against u q} . The following applies to the sum of the discriminator output voltages

^U Fm ^β ifi Υ ^U 1 ^{(t) dt +} 7 ^U 2 ^{(t) dt f} " ^U 3 ^{(t) dt}

; = U ₀ ^ sin (w - (T) (0)

; an Eq. (6) corresponding course. The difference by the factor two arises because Eq. (7) only goes over a half-wave. When using a signal circuit that extends over both half-waves the sum of the three discriminator voltages Eq. (6). In Fig.

I2c, the three discriminators are only offset from one another by 120 °.

- 7 -

509814/0198

The angle setpoint (T 'is used as a phase shift of the feed span = input of rotor 5:

u _o = U ₀ sin (ot + ~) (9)

being the tension
u _o = U ₀ sin (,
from input device 11 is supplied.

u = U sin (cat + ι "- ')

The sum of the discriminator output voltages U _Fm = Λ \ T ^U 1 ^{(t) dt +} Y ^U 2 ^{(t) dt + 7} T ^U 3 ^{(t) dt} 7 ^(1O)

² ^ τ -fr, 4 * - /

is equal to the result of Eq. (8th) . ~~ -

The circuit of the discriminators D, D ", D_ is shown in FIG. 3. They each consist of two inverting amplifiers with a gain of -1, the measuring alternating voltage u or v ;. u ₉ or u., is fed to the input of the first amplifier, the output of which is connected to a switch S or S_ or v ;. Sg and is also connected to an input of a second inverting amplifier, the output of which in turn is connected to a switch S or V ;. S_ or S- is connected. Two of the switches, S ,, S. bzv ;. S ", S ₅ or S-. , Sg lead via a resistor R to the input of a summing amplifier 11, at the output of which the negative, rectified error voltage -U_ appears. Because of the evaluation that goes over both half-waves, two switches are required for each input voltage, one of which is closed while the other is open. During one switching period, for example, U ₁ is switched through to the summing amplifier 11 during the other switching period. The capacitor C is used for smoothing.

The actuation of the switches S to S takes place in such a way that, as shown in FIG. 4, a basic time unit A or B or C or I) or E or F after switching off a switch Sj bzx /. ίί_ or S ₃ cyclically successively the next switch, ie S ₂ or S _{3 is} switched on for the duration of three basic units. At the same time, the condition applies that the

5098U / 0198

Switch S. or S ₁ - or S, are not switched on as long as 4 bb

S ₁ or S "or S, are switched on and vice versa. The ent =

J. £ * «5

j standing voltages u _q . , υ _ς? , u_-, are shown in FIG. 4c and are sent to the summing amplifier 11 to determine the rectified error voltage.

^: In Fig. 4, the measurement voltages U ₁ - U _{3 of} the encoder synchro 3 for the angle actual value w = 0 ° are shown as an example. If the angle range 2 K is divided into six sections A to F (Fig. 4), the switching functions apply to the control of the switches:

S ₁ S ₄

Op -7 O ₁ -

^S 3 ⁼ ^ ^S 6
5 shows a block diagram in which an oscillator 12 is connected to a counter 13 and a reference counter 2o. The output of counter 13 is connected to a second counter 14, a zero signal output from counters 13 and 14 being led to the input of a zero coincidence element 15, the output of which is connected to an input of the AND element 19, the output of which is the Setpoint counter 2o sets. The zero output of counter 14 is also connected to a decoder 16 which, via an output 17, switches S, -S-. controls. A memory 18, in which the setpoint value is stored in digital form, is connected to a second input of the AND element 19. The target value counter 2o j is connected to a fundamental wave filter F, at the output of which: 21 the normal alternating voltage u for feeding the rotor 5 of the encoder synchro 3 is present. If the measurement accuracy and rain accuracy are, for example, 0 _f l °, the operating frequency of the normal alternating voltage u must be derived from a clock frequency that is at least a factor of 3,600 higher. If at = •, for example, the operating frequency is 4oo Hz, the result is a clock frequency f equal to 1.44 MIIz. This clock frequency is recorded in two counters 13 and 14 or 2o. The reference counter 13 and 14 then emits the signals for the switches Sj to Sg of the discriminators D., Ό2, D_ via a decoder 16; the setpoint counter

_ Q

5098U / 019 8

is set at each zero coincidence of the reference counter 13 and 14 via the zero coincidence element 15 to the target value. Reference counters 13 and 14 and setpoint counters 20 are thus phase-shifted by the amount of the angular value c , as indicated in FIG. 2c.

A filter F filters the uneven harmonics, which interfere with the controlled rectification, from the square-wave output output signal of the setpoint counter 2o.

Is a revolution of the rotor, for example a distance of 2 "10 ⁿ .m assigned (for example 2o mm), so v / ground coming from the clock oscillator 12 pulses by a factor of 1.8 reduced. The target value = counter 2o then has only 2,000 different states. Such measures are necessary in particular to adapt the spindle pitch or pinion diameter to the desired measuring range. To implement a pulse multiplier, for example with a resolution of 18 bits, only three integrated circuits are required. Accumulating errors do not arise in the target value counter 2o, since this is reset to the value of the target value with every zero coincidence of the reference counter 13 and 14.

All phase errors occurring between the target value counter 2o and the inputs of the discriminator D., D-, D ₃ Fig. 2 influence the accuracy of the position measurement. It happens in particular through the filter F _q and the supply line to the encoder synchro 3. While the influence of the phase shift through the filter can be reduced, for example, by supplying this filter with voltages with a lower harmonic content and thus lower filter attenuation is required (Undershoot method according to FIG. 6d) one can also measure all phase errors occurring between the target value counter 2o and the discriminator inputs with a relatively simple circuit addition and take them into account in the target value specification.

- Io -

509814/0 198

2 3 A Π! '! O

- Io -

Fig. 6a shows the course of the output voltage u of the target value = Counter 2o from Fig. 5. The coefficients of the Fouricr series of these Square waves are (coefficient of the fundamental wave = 1 ge = puts)

a _n = 1 (n = 1, 2, 3 ...) (11)

The even harmonics become ineffective, the un ~ However, even-numbered ones are fully included depending on the phase position. Should, for example, the proportion of the third harmonic in the synchro supply voltage be only -50 dB, the filter F (Fig. 5) would have to attenuate this frequency by approx. 40 dB compared to the fundamental wave.

The subharmonic method with a small harmonic content is applied in such a manner that, as shown in Fig. 6b and 6c zv / ei square waves U., provided whose Peiriodendauer -t ρ by a factor of 1 and ρ (ρ is the greatest possible integer) are shorter than that of U _n :

^f u1 - ^f o

^f u2 » ^f op

If the _{non-equivalence link of U 1} and U ₃₁ and their negation are now formed, the oscillation shown in FIG. 6d arises .

^U 3 "( ^U

whose Fourier coefficients decrease with the square of the order.

- 1 / n ² (15)

A filter F. (FIG. 7a) only has to attenuate the third harmonic by approx. 30 dB compared to the fundamental wave, so that the filter can be of a lower order, which means that less phase shift occurs. A circuit for generating the undershoot is shown in FIG. 7a; the factor ρ = 15 was chosen so that the

- 11

509814/0198

derived in Fig. 5; Resolution of 1: 36oo is retained. In Fig. 7a the double oscillator frequency 2 f is divided once in the unit 22 by the factor ρ and the resulting voltage on the one hand by division by the factor 2 · ρ in the units 23, 24 to generate U. and on the other hand in the units 2 5 and 26, on the other hand, divided by the factor 2 (p rl) _{to generate the voltage U 3.} A further division by a factor of 480 = 2p (p-ti); p = 15 is made in the unit 29, at the _training: gang the voltage U is ent. The two voltages UJJ and U * are:

a lofrisehen unit 28 which, together with the lagging unit 28, undertakes the operation provided in equation (14). As a result, the voltage U ₃₁ arises, which leads to the filter F, at whose output the voltage u arises. A further reduction in the filter order is possible in that a control ^{v /} ie in FIG. 6e is carried out. A circuit for guiding the process; ir.t shown in Fig. 7b. If one controls an integrating element 3o with the output voltage of the non-equivalence link in FIG. 7a, connection point A, that at u_ = 1 a positive voltage 1- u and at u_0 a negative voltage of the same amount

X A -

If the voltage -u reaches the integrator 3o, it arises at the output of the integrator 3o the voltage curve shown in Fig. 6e. The Fouricr coefficients are now

\ - 1 / n ³ (16)

Since the third harmonic occurs here at approx. 3o dB, which is weaker than the fundamental, an attenuation of approx. 2o dB is required for this harmonic in filter Y (Fig.

The lower the filter attenuation required, the lower are also the tolerances of the phase response and the influence of frequency variations. The following table shows the order the required filters

V ^b n

1 / n

1 / n ²

1 / n ³

Attenuation pro
Frequency decade
80 dB dB - l? Order of
Filters
H - 60 dB & 098 U / iM 3 hO 2

The counters 22 to 26 required to generate the undershoot can no longer be set to any desired value. Therefore, as indicated in FIG. 5a, setpoint counter 2o is not set from 13 to 24 when there is a zero coincidence, but rather to zero when the setpoint and reference counters 13 and 14 coincide.

FIG. 8 shows the circuit elements described so far, the oscillator 12 feeding the unit 32 via a scale unit 31, into which the setpoint value, as described in FIG. 5, is input. Furthermore, the undershoot generator 33, as shown in FIG. 7a, is fed by 12. The voltage U is fed through a filter F into the synchro-transmitter 3 and additionally = borrowed a phase corrector 36, which on the one hand the oscilator frequency is entered and on the other hand the measurement voltage U., ^ü ₂ f U ₃ and the counter 34 , the decoder 37 causes an error voltage U in the discriminator 38. The Phasenkorrek = gate 36 is supplied with the clock frequency removed, lighter before the filter synchro transmitter normal voltage U and the measuring voltages U., U _2, Vj of the synchro transmitter. 3 The output signal of the phase corrector 36 sets the reference counter 34 taking into account the phaeon shifts occurring in the filter, synchro- transmitter and in the supply lines.

In FIG. 9 , the phase corrector 36 according to FIG. 8 is shown in detail . The measured voltages U., U, U- are squared in the multiplier stages 39 and fed to a summing element. Here, the relationship wicd

ρ ρ ρ ρ u _o = U ₁ ^ + U ₂ * + U ₃ * (17)

used, which allows a recovery of the synchronous normal voltage ge =. A pulse shaper 4o generates phase correct primary signals te ψ from the sum voltage, which are sent to the control unit. 41 * and the phase counter 42 shows (Fig.lo). In the upper part are the voltages U and U? ^; shown, which are referred to a signal change from 1 to O or vice versa, or d _{ulo ά} υ f. When the signal occurs, the phase counter 42 starts, the content of which is in the

_; »Are supplied. The interplay of the individual signals with '■ the control unit 41

I - 13 -

5098U / 0198

is shown in the lower figure of Fig. Io. When the d f signal occurs, the phase counter 42 stops until the next d i occurs. Signal, where the phase shift is detected again. The now following d «. -Signal causes the phase counter 42 to count down at twice the frequency; when the counter 42 crosses zero, the reference counter 34 (FIG. 8) is set to zero
puts. Reference counter 34 thus begins to count with a delay. If you want to extend the phase detection over several periods of the operating voltage, you can do this with a corresponding reduction in the up counting frequency of the phase counter 42 and a demand for the control circuit 41 without great effort. This makes the phase correction particularly insensitive to Stör =
signals.

! - 14 -

509814/0198

Claims (12)

- 14 - S chu tz claims Measuring device for a night! Control system with an actual value transmitter, a setpoint transmitter and an evaluation device for setting predefinable angular values on the axes of mechanical pivoting or rotating devices v / ie rotating antennas, machine tools, gyroscopic platforms for navigation purposes, etc., whereby the actual value transmitter is a known, inductive position measuring system is formed having a plurality of induction coils, a part of the Induk = tion coils from a normal alternating current of known size is applied and the other part of the induction coil generates at least a = a function of the winding adjustment of a variable to be monitored axis Meßwechselspan voltage, dadurc h gekennzeichne t that which contains a circuit arrangement made up of electronic components by means of which the control deviation voltage is produced for the comparison of the actual and nominal value and for generating the control deviation voltage proportional to the difference value llbar, evaluable and can be fed to the actuator of the follow-up control system. 2. Measuring device according to claim 1, characterized in that the circuit arrangement contains v / at least one controllable rectifier, that each controllable rectifier is assigned a measuring AC voltage, that if there are 3 controllable rectifiers, these are offset by 2 t / 3 ° on = switchable, that the activation of the controllable rectifier depends on the difference between the nominal value and the angular value w against the phase of the normal alternating voltage and that the resulting voltages can be summed at the output of the controllable rectifier. 5098U / 0198 2343110 3. Measuring device according to claim 2, characterized in that the setpoint can be entered in digital form in the evaluation device that an oscillator is provided whose Frequency is an integral multiple of the normal alternating voltage = voltage frequency, that the oscillator frequency in two behind = interconnected counters can each be divided by an integer, so that in each case one of the counters indicates the zero value gender output is led to a zero coincidence element that the output of the zero coincidence element with one input an AND gate is connected, that the other input of the AND gate with a device for storing the di = gitalen setpoint is connected in a third counter that the setpoint number stored in the third counter has a Another input can be continuously reduced to V7ert zero by the oscillator oscillation and that a value of zero This counter uses a normal alternating voltage for supply that is shifted by the setpoint value and is routed via a fundamental wave filter of the inductive position measuring system is available. 4. Measuring device according to claim 3, characterized in that the second counter has a logic circuit for actuation the controllable rectifier contains. 5. Measuring device according to claim 4, characterized in that the controlled rectifiers in the manner of phase angle rectifiers are designed as switches that depend on ity of the phase of the normal alternating voltage open and close that each measuring alternating voltage of the inductive location = measuring system are assigned two switches, one switch of the one measuring voltage and the other Switch of the inverted measuring voltage is assigned that in each case two switches assigned to one another via ei = NEN resistor is led to the input of an amplifier, whose input and output via a capacitor and a Resistors are connected in parallel to each other (integrator), - 16 - 50981 A / 0198 23491 ¹ O are interconnected and that at the output of the amplifier ι the sum voltage of all rectified measuring alternating voltages ^{: are} present. 6. Measuring device according to claim 5, characterized in that the basic unit for the actuation time of the switch 1/6 of the oscillation period of the measuring AC voltage is provided that each = the switch is periodically open for three basic units and closed for three basic units, that cyclically repeating after opening of the first, the positive Meßwechsel = voltage switch associated with the next, second po = ^s tuitive measuring alternating voltage switch associated with a gobies = integral after the elimination of the first switch is turned on and that according to the * third, positive measuring voltage switch associated with a basic unit after opening the second switch closes, this opening and closing rhythm is repeated cyclically and that for the corresponding switches assigned to the inverted measurement voltages, the second switches are closed if the first switches are open and vice versa. 7. Device according to claim 1, characterized in that a circuit arrangement is provided to reduce the Fourier coefficient of the harmonics with the square of the order, the input of which twice the oscillator frequency is entered, that the frequency is divided by the factor ρ that the resulting AC = Schaltungsan two systems are respectively supplied, wherein the AC voltage to a first circuit configuration by the factor 2p to form ei = ⁿ he voltage u., and in a second circuit arrangement by \ the factor ifp + l) is converted to form a voltage u_, and that both voltages are entered into a logical unit, with the resulting voltage U, being determined from ι the logical connection u, complementary u, -u, equivalent u _? , and that the resulting alternating voltage is a filter P feed = bar, which the third harmonic by about 3o dB compared to ι the fundamental wave attenuates. ! ^ third of the 509814/0198 8. Measuring device according to claim 7 _f, characterized in that the number 15 is provided as a factor ρ. 9. Measuring device according to one of the preceding claims, characterized in that to reduce the Fourier coefficients = th by a single degree of the arrangement according to claim 8, an integrator is connected downstream, the input of which is a value of the output voltage u at point A of a positive voltage + ux and a value u, = ο are subjected to a negative voltage of the _{same magnitude -u and that the integrator is followed by a filter F 2} which has an attenuation of approximately 20 dB for the third harmonic. 10. Device according to one of claims 1 to 9, characterized ge = indicates that a phase corrector is provided, the ι with the clock frequency, with the Be = removed in front of the filter drive voltage and as well as with the output alternating voltages ; of the inductive position encoder is controllable. I. 11. Measuring device according to claim Io, characterized in that that the output signal of the phase corrector the reference counter taking into account the in filter, the inductive position measurement = systems as well as the supply lines. 12. Device according to claim 11, characterized in that: the three measured value voltages in a multiplier j multiplied by itself, i.e. squared and summed; be that the total voltages via a pulse shaper ei = ; nem control unit is fed, which also the operating = voltage and double the oscillator frequency is supplied; that at two outputs of the control unit signals for the number im = pulse the counting direction is fed to a phase counter, J that a corresponding one at zero crossing of the phase counter ; Signal ': is returned to the control unit and that at the control = werk also an output of the reference counter is set to zero. 509814/0198