DE2249390A1 - DIGITAL EMF KNIFE FOR HALL GENERATOR - Google Patents

Description

Digital EMF meter for Hall encoder The present invention relates an EMK-Nesser for Hall sensors, in particular a digital EMK-Nesser for Hall sensors, and can be used in various devices based on the Hall effect A digital EMF meter for Hall sensors is known (see e.g. bElectronic Equipment News ", v. 8. No. 9, 1966, so 50 - 53), which contains a Hall sensor, from one pair of counter electrodes to a supply source and the second to a voltage-code converter connected to a digital indicator. The ones from second counter-electrode pair taken output voltage of the Hall encoder is through encoded by the voltage code converter and registered with the aid of the digital indicator.

There are also analog devices for measuring Hall sensor EMF, where the effect of the non-equipotential voltage on the EMF of the Hall sensor excluded (see e.g. SU patent applications 1 303 152 / 18-10, 1 395 344 / 18-10, t 469 319 / 18-10). Such devices can have a hall sensor with two pairs of counter electrodes, one of which is connected to the supply source via a changeover switch and the second connected to an indicator of the Hall sensor EMF via the switch is. The switch is used to alternately connect pairs of electrodes of the Hall sensor to the supply source and to the indicator of the Hall sensor EMF. At the moment when one pair of counter electrodes is connected to the supply source is, the second is in communication with the display device, and vice versa, if the The second pair is connected to the supply source, the first is connected to the display device in connection.

As a result of the irreversibility of the Hall sensor with regard to the Hall EMF and its reversibility with respect to the non-equipotential voltage is the output voltage taken alternately by pairs of counter electrodes in one work cycle of the switch from the sum of the Hall-EXK and the non-equipotential voltage and in the second from their difference.

The deflection of the EMF indicator through a certain angle is proportional the mean of the absolute levels tapped by each pair of counter electrodes Output signals, d. H. the value of the Hall EMF, and thus of the non-equipotential voltage independent.

The listed facility sets a multiple in this way Switching between pairs of electrodes and the presence of a mean value display device for the absolute level of the output signals of the Hall sensor with a high time constant in advance.

The well-known digital EMK meter for Hall encoder, however, has one Number of disadvantages.

First, a low measurement accuracy of weak signals from the Hall sensor, those caused by the influence of the corrected, but time- and temperature-unstable, non-equipotential voltage the emf of the hall sensor is conditional.

Second, the impossibility of measuring the true value of the Hall emf in those cases when the non-equipotential voltage is only cumbersome from the emf of the Hall giver is to be separated, d. H. when the shape of the indicated signals is the same.

Third, a considerable measurement time caused by the need caused by the manual zero point setting of the device before each measurement. This circumstance complicates or makes the use of the knife for registering the EMF from Hall sensors impossible, their change time is less than the required Zero correction time is.

In addition, with this knife the measurement is fully automated the Hall sensor EMF difficult to implement.

The aforementioned analog device for measuring the Hall sensors -EMX has the following disadvantages: firstly, an insufficiently high measurement accuracy of the Hall EMF, which is caused by the influence of commutation disturbances; second, a minor one Operating speed of the device because of the need for careful sieving the output voltage of the Hall sensor; third, inadequate reliability the device, which is caused by repeated actuation of the switch.

The use of the described Hall sensor with an electrode switch in the known digital Hall EMF meter, however, appears impossible because in the voltage code converter of the digital EMK knife in each subsequent work cycle of the switch Loss of information regarding the value of the output voltage to be measured Hallgebers takes place in the previous work cycle.

The invention is based on the object, eliminating the mentioned Disadvantages of creating a digital Hall EMF meter for Hall sensors that do not have any Requires specially provided previous zero point adjustment of the device.

This task is performed with a digital EXK knife for Hall sensors, in which the counter-electrode pairs of the Hall sensor are connected to a supply source via a switch and at one with voltage code converter connected to a digital indicator are alternately connectable, solved by a unit for fixing the end time the coding, its input with the voltage code converter and its output with connected to the switch and the same converter.

The invention is further developed by a phase-sensitive element, this is a signal to act on the voltage code converter in the event of an increase the Hall sensor EMF generated by Hall sensor non-equipotential voltage, with vom phase-sensitive element a first input to the output of the switch, a second input with the supply source and the output with the voltage code converter connected is.

The inventive digital EMF meter for Hall sensors includes the Influence of the non-equipotential voltage on the EMF to be measured completely, whereby The accuracy, sensitivity and operating speed of the device are significantly increased will.

The invention is described below using an exemplary embodiment and the accompanying drawings.

They show: FIG. 1 the block diagram of the digital EMF meter for Hall sensor according to the invention; Fig. 2a shows the time course of the Hall sensor applied constant magnetic induction according to the invention; Fig. 2 b shows the timing of the Hall sensor feed current and the reference voltage according to the invention; Fig. 2c shows the time course of the total output voltage of the Hall sensor according to the invention; Fig. 2 d the comparison of time courses of the absolute Values of the Hall sensor output voltage with the linearly variable compensation voltage according to the invention; Fig. 2e the timing diagram for code change in the voltage code converter in the course of the coding of the output voltage of the Hall sensor according to the invention; Fig. 2 f the temporal course of the pulse signal at the output of the voltage code converter according to the invention; 2g shows the voltage profile over time at the output of the unit for fixing the end time of the coding according to the invention; Fig. 2 h the Voltage curve over time at the output of the phase-sensitive element according to FIG Invention, and FIG. 2j shows the time course of displays of the digital display according to the invention.

The digital EMF knife constructed according to the invention for Hall sensor contains: a Hall sensor 1 (Fig. 1) with two pairs of counter electrodes 2) 3 resp. 4, 5, which via a switch 6 with a supply source 7 and one to a digital Indicator 9 connected to the voltage code converter 8, as well as a unit 10 for fixing the end time of the coding, whose input with the converter 8 and its output are connected to the switch 6 and the same converter 8 is.

The changeover switch 6 is used to connect some of them alternately Pairs of electrodes, e.g. B. 2, 3, the Hall sensor 1 to the power source 7 and others Couples, e.g. B. 4, 5, and the voltage code converter 8 and then vice versa. As a toggle switch 6 various contactless and contact switching devices such as electromechanical, electronic etc. are used.

The voltage code converter 8 can be used as a time-pulse, pulse-frequency and pulse code converters are carried out.

The unit 10 is used to fix the end time of the coding to determine the point in time at which the process of coding the Hall sensor output voltage is terminated by the converter 8, and then to form a control signal, which acts on the switch 6 and the converter 8. The mentioned unit 10 can ensure the measurement of the Hall sensor EMF at least in two cycles.

The digital knife can also use a phase sensitive Element 11 are provided, of which an input to the output of the Changeover switch 6, the second input to the supply source 7 and the output to the voltage code converter zer 8 is connected.

The setup works as follows: Before starting the measurement the Hall sensor EMF is the initial setting of the switch 6 (Fig. 1), des Voltage code converter 8 and the unit 10 for fixing the end time of the Coding.

When exposed to z. B. a constant magnetic induction B (Fig. 2a) on the Hall sensor 1 (Fig. 1) and when it is fed z. B. with sinusoidal Alternating current i (Fig.

2b) via a pair of counter electrodes 2, 3 (Fig. 1), which are in the rest position of the switch 6 are connected to the supply source 7, arises at the second pair of electrodes 4, 5 a voltage U1 (Fig. 2c), which is made up of a Hall EMF ex and a non-equipotential voltage U composed.

p The non-equipotential voltage Up results from the continuity of the current i through the electrodes 2, 3 (Fig. 1) of the Hall sensor and is by application of the electrodes 4, 5 mentioned at the outset at non-equipotential points of the plate of the Hall encoder 1 conditional. The value of the non-equipotential voltage Up is specific Resistance of the Hall sensor material dependent and proportional to the supply current value.

It is assumed that the Hall emf ex and the non-equipotential voltage U are in phase (Fig. 2c), i.e. H.

p is the instantaneous value of the electrodes 4, 5 of the Hall sensor (Fig. 1) tapped output voltage U = (Exm + rpm) sin w t, where E and U are maximum values of the Hall EMF and the xm pm non-equipotential voltage and w 0 is the angular frequency of the supply current 1.

At the time t (FIG. 2d) of the start of the measurement, the voltage code converter codes 8 (Fig. 1), for example, designed as a time-to-pulse converter and via the Changeover switch 6 is connected to electrodes 4, 5, the absolute value 1u11 (Fig. 2d) the output voltage of the Hall encoder 1 (Fig. 1) by making it z. B. with a compares linearly variable compensation voltage Uc (Fig. 2d).

The result h1 of the coding (Fig. 2) is in the form of a static Digit codes H1 formed and stored in the memory of the voltage code converter 8 (Fig. 1) saved.

If the converter 8 is designed as a pulse-code converter, must one in the circuit of the digital Hall sensor EMF meter in addition to that of this converter type existing bidirectional counter an additional bidirectional counter (not indicated) between the voltage code converter 8 and the digital indicator 9 arrange the storage of the coding result of the Hall sensor output voltage U1 is determined.

The point in time t1 (FIG. 2d) of the completion of the coding process for the absolute value of the output voltage U1 of the Hall sensor 1 (Fig. 1), the The end of the first cycle I of the measurement (FIG. 2) is carried out by the unit 10 to fix the end time of the coding (Fig. 1) fixed at the input at this moment a pulse signal U8 from the converter 8 appears (FIG. 2f). The unit 10 to fix the end time of the coding (Fig. 1) generates a control signal U10 (Fig. 2g) which is sent to the voltage code converter 8 (Fig. 1) and the switch 6 acts.

The voltage-code converter 8 switches to the operating state the coding of the following value of the output voltage of Hall sensor 1, without that the end result H1 (Fig. 2e) of the coding of the first clock I is deleted. When the switch 6 is tilted (Fig. 1), the electrodes 4, 5 of the Hall sensor 1 to the supply source 7 and the electrodes 2, 3 to the voltage-code converter 8 connected. This corresponds to the beginning of the second cycle II (FIG. 2d) of the measurement the output voltage of the Hall sensor 1 (Fig. 1).

As a result of the irreversibility of the Hall sensor 1 with regard to the Hall EMF ex and its reversibility with regard to the non-equipotential voltage U is im second cycle II of the p measurement of the instantaneous value of the output voltage U2 (Fig. 2c) of the Hall sensor 1 (Fig. 1), which is picked up by the electrodes 2, 3, the same U2 = (Exm - rpm) sin w t with regard to its inversion, which is given by corresponding Connection of the contacts of the switch 6 is provided with one another.

The irreversibility of Hall sensor 1 has the consequence that the Phase shift angle between the Hall EMF and the non-equipotential voltage changes by 1800 when the counter electrode pairs (2, 3 and 4, 5) are changed.

Due to theoretical and experimental investigations are the values E and U for an isotropic Hallxm pm encoder 1 in both cases treated exactly the same. The phase shift angle between them is 0 ° respectively. 1800 (s. z. B. the contribution by R. F. Wick, "Solution of the problem of the electric Hall field in Germaniumgyrator ", Journal of Applied Physics, vol. 25, No. 6, 1954).

During the second measure II of the measurement, the coded with his Input via the changeover switch 6 with the electrodes 2, 3 connected voltage-code converter 8 the absolute value | U2 | 12I) (Fig. 2d) of the output voltage of Hall sensor 1 (Fig. 1) and sums the current code h2 (Fig. 2e) with that in its memory stored code H1. The end time t2 (FIG. 2d) of the coding of the output voltage U2 (Fig. 2c) of the Hall sensor 1 (Fig. 1) is used by the unit 10 for fixing the Determined end time of the coding, which generates a stop signal for the measuring process (the coupling via which the mentioned signal acts on the voltage code converter 8, is not shown in Fig. 1).

The entire work cycle of the EMF knife is therefore carried out in two cycles I and II (Fig. 2c). In the automatic operating state of the digital knife, it is Cycle repeated many times.

After completion of each work cycle, the voltage code converter is used on the one 8 connected digital display 9 (Fig. 1) reading the measurement result Nx (Fig2j) for the EMF of Hall sensor 1 (Fig. t). This result depends on the non-equipotential voltage U does not start, since there are 8 pieces of information in the converter in two p cycles I and II of the measurement stored via the total output voltage U (Fig. 2c) of the Hall sensor 1 (Fig. 1) whose absolute value is equal to | U # | = | U1 | + | U2 | = 2 EXm.

It should be emphasized that the result obtained is only for the The case applies if Eim> rpm. According to the rules of the algebraic operation with absolute numbers and assuming that Exm <U is the absolute The value in pm of the total voltage is not proportional to the Hall EMF, but to the non-equipotential voltage, d. H.

#U ## = # Exm + U # + # Exm - rpm # #Exm + U I + # Exm U = Exm + rpm - Exm + Upm = 2U in pm in pm in pm pm pm In this context, when Eim <U die Subtract absopm luten values of the Hall sensor output voltages to get a correct one Get result, d. H.

IUSI = #Exm + Upml- IECm - Upm # x 2Ex To determine an excess the non-equipotential voltage of the Hall sensor via its EMF is used by the phase-sensitive Element 11 (Fig. 1).

The peculiarity of the work of the phase sensitive element 11 is in the following: If in both cycles I and II of the measurement the reference signal Uo (Fig. 2b) from the supply source 7 (Fig. 1) one of the inputs of the phase-sensitive Element 11 is supplied, and that of the counter electrode pairs 4, 5 and 2, 3 tapped output signals U1, U2 (Fig. 2c) of Hall sensor 1 (Fig. 13 at E> rpm are in phase, so in pm the signals U and U1 (Fig. 2b, c) are in the first cycle I 0 U1 (Fig. C) with EXm <U in phase and the signals Uo and U2 (Fig.

2b, c) in phase two in the second cycle II. Such a condition results If the output voltage U2 (Fig. 2c) of Hall sensor 1 (Fig. 1) in the second measure II.

The information about the phase change between the voltages U and U2 at E <U is obtained with the help of the phase 0 2 in the pm sensitive element 11. The output signal U11 (Fig. 2h) of the phase sensitive element 11 (Fig. 1) becomes used to change the state of the voltage code converter 8, which in this case the Final results H1 and N2 (Fig. 2s) of the coding of two clocks I and II subtracted.

The introduction of the phase sensitive element 11 into the circuit the digital Hall sensor EMF meter significantly increases the sensitivity of the device, since there is the possibility of an EMF of the Hall sensor to its, its size below is the value of the non-equipotential voltage.

In addition, in the absence of the magnetic field, i.e. H.

when ex = 0, and when the non-equipotential voltage Up is present Zero because the phase shift angle between the non-equipotential voltage U and the reference signal Uo changes by 180 from cycle I to cycle II (Fig.

o 2b, c) and thus the same results of the coding H1 = H2 are subtracted in both cycles (H1 - H2 = 0).

In comparison with the well-known Hallgeber.ENK-M.ssern, the present EMX knife a higher accuracy, sensitivity and working speed and allows to determine the true value of the Hall EMF, the measuring process is fully automated.

Claims (2)

Claims 1. Digital EMF meter for Hall sensors, in which the counter electrode pairs of the Hall sensor via a switch to a supply source and to one with a Voltage code converter connected to the digital display can be connected alternately are, g e k e n n n z e i c h n e t by a unit (10) for fixing the end time the coding, its input with the voltage code converter (8) and its output is connected to the switch (6) and the same converter (8). 2. Digital EMF meter for Hall sensors according to claim 1, characterized by a phase-sensitive element (11), which sends a signal to act on the Saving code converter (8) in the event of an increase in the Hall sensor EMF due to Haligeber non-equipotential voltage generated by the phase-sensitive element (a first input with the output the switch (6), a second input with the supply source (7) and the output is connected to the voltage code converter (8), Blank page