SU764485A1 - Method and device for measuring instant values of periodical magnetic fields - Google Patents

Description

proportional to the derivative of the induction field over time, fixing the leading edge of the signals of the cut-off moment of the signals relative to the leading edge and changing the delay within the duration of the signals, the cut-off electrical signals are compared with the adjustable reference signal for a fixed interval time, and when the signals are equal, the magnetic field is determined by the magnitude of the reference signal,

A known device for measuring instantaneous values of periodic magnetic fields, comprising an inductive magnetic field sensor, a DC voltmeter, a series-connected front-edge fixation unit, a delay element, and a key connected to the sensor, are inserted a series-connected formation unit (fixed time interval, element And, the second key and the capacitive filter, the output of which is connected to a DC voltmeter, while the filter input and the output of the second key are connected to the output the first key, the second output of the delay element is connected to the second input of the AND element, and the inputs of the delay element and the fixed time interval shaping unit are connected to the output of the leading edge fixation unit.

The method of explanation of the diagram shown in FIG. 1, and the device is a block diagram of FIG. 2

The field B (t) (Fig. 1) is converted by the sensor into a voltage U (t) proportional to the time derivative of the floor.

At a given time, the voltage is cut off, and the cut-off voltage during the time f is compared with the reference voltage f / o-.

Equality takes place if the area of the rectangle with height f / o and the base / f and the figure formed by the curve of the cut-off voltage with the base / o / o are equal,

1 U (t} dt 5 (/ o).

It can be seen that the value of the readings f / o does not depend on the pulse frequency of the field.

The device contains (Fig. 2) induction sensor 1 magnetic field, keys 2 and 3, a DC voltmeter 4, a fixing unit 5 of the leading edge of the sensor signal, a delay element 6 of the cut-off moment; block 7 of the formation of a fixed time interval, the element And 8 and the .RC filter 9.

The device works as follows. In the initial state, the capacitor

filter 9 bits The keys 2 and 3 are locked by the potentials at the outputs of the delay element 6 and the element 8. At the moment of the occurrence of the floor, the fixing unit 5 of the leading edge generates a pulse triggering the delay element b of the cut-off moment and the block 7 forming a fixed time interval.

Element b generates a pulse whose duration is equal to the delay time of the cut-off moment. From the direct output of the element b, a trigger pulse is removed, under the action of which the key 2 is closed, and the EMF of the sensor is applied to

the filter.

Block 7 generates a trigger pulse of a duration equal to a fixed interval. The key 3 is kept in the closed state until the moment of cut-off.

since from the inverse output of the delay element b to the input element PI 8 receives a locking pulse. At the moment of cut-off / o the delay element b returns to the initial state and locks key 2. At the reverse output of the delay element b, an unlocking potential is established. Key 3 is locked and held in this state until the end of a fixed time interval / ph. Thus, during the delay time, the capacitance of the filter 9 is charged under the action of the EMF of the sensor I, and then up to time / f the filter 9 is closed on the common bus and its capacity is partially discharged.

Until the end of the period, the charge on the tank does not change. The process then repeats and the capacitance receives a new charge increment. The filter constant 9 is selected such that, in one cycle, the stress on the capacitance changes by a small amount.

The accumulation of charge ceases at the moment when the voltage across the capacitor is equal to the sensor's emf averaged over the range ff. The steady-state voltage is measured by a voltmeter 4, and then the field is determined by the above formula.

From the description it can be seen that the capacity of the filter 9 serves as a source of reference

., and the comparison process proceeds automatically by changing the charge capacity.

The method and the device according to the method ensure that the readings are independent of the pulse frequency of the field. The method is especially effective when measuring fields of short duration:

Claims (2)

Formula invented and I. A method of measuring instantaneous values of periodic magnetic fields, based on converting magnetic field induction into electrical signals proportional to the derivative of FIELD induction over time, fixing the leading edge of signals, delaying the cut-off time of signals relative to the leading edge and changing the delay within the duration of the signals, differing By the fact that, in order to increase the sensitivity and accuracy of measurements, the cut-off electrical signals are compared with the adjustable reference signal during phi densed time interval whose duration is less than the repetition period of signals, and signals when equality in magnitude of the reference signal is determined by the magnetic field. 2. A device for implementing the method according to claim 1, comprising an inductive magnetic field sensor, a DC voltmeter connected in series with a leading edge fixing unit, a delay element and a key connected to said sensor, characterized in that a series-connected unit for forming a fixed time interval, element I, is inserted into it, the second key and the capacitive filter, the output of which is connected to a DC voltmeter, the filter input and the output of the second key are connected to the output of the first key, the second output of the delay element to the second input of the element And, and the inputs of the holder and the fixed time interval shaping unit is connected to the output of the leading edge fixation unit of the signals. Sources of information taken into account in the examination: 1. USSR Author's Certificate No. 390484, cl. G 01 R 33/12, 1973. 2. The measuring technique. Ed., Shramkova E. T., M., 1975, p. 73. t and. from G. N J t