SU1712937A1 - Digital automatic coercimeter - Google Patents

Abstract

The invention relates to magnetic measurements and can be used to measure the coercive force of ferromagnetic products in an open magnetic circuit. The purpose of the invention — improving the measurement accuracy — is achieved by introducing 13 pulses into the divider device, a peak detector 10, a differentiating circuit: 11. The device also contains a Helmholtz coil 1, a linear current generator 2, a control unit 3, a threshold unit 4, an AND 5 element, a pulse counter 6, a digital indicator 7, a trigger 8, a ferrosonde 9, and a clock pulse generator 12. 2 ill. ≫ & «• Chv ^ Ik > & CJ • h

Description

This invention relates to digital automatic coercimeters and can be used to measure the coercive force of ferromagnetic products in an open magnetic circuit.

The purpose of the invention is to improve the measurement accuracy.

Figure 1 shows the functional diagram of the coercimeter; Fig. 2 is a time chart of the current.

The digital automatic coercimeter consists of a Helmholtz coil 1, the input of which is connected to the first output of the linear current generator 2, successively connected control unit 3, linear current generator 2, threshold unit 4, And 5 element, counter b of pulses and digital indicator 7. First input element 5 is connected to the output of the trigger 8, the input of which is connected to the output of the fluxgate 9 and the input of the peak detector 10. The output of the latter through the differentiating circuit 11 is connected to the input 3 of the control unit, and the output of the generator 12 clock pulses Through a divider 13 pulses connected to the third input element And 5. In the device entered the test product 14.

Coercimeter works as follows.

When the supply voltage is applied to the coercimeter and product 14 is installed with a rod (not shown) in the Helmholtz 1 coil, control unit 3 turns on the linear current generator 2 and a linearly increasing current is applied to the winding (gap O - a in Fig. 2a) . As the current increases, magnetization of the product 14 occurs, which corresponds to an increase in the signal at the output of the fluxgate 9. When saturation of the product 14 is reached, which corresponds to a current of 1H1 (point a in Fig. 2a), the signal of the fluxgate 9 reaches a maximum value through peak detectors: torus 10 and The differentiation circuit 11 is supplied to the control unit 3, which acts on the linear current generator 2. At this command, the current decreases to zero (point b in Fig. 2a) and at the moment the current passes through zero, a change in its polarity occurs. A reverse polarity current is supplied to coil 1. This demagnetizes product 14. At the same time, a signal is sent from linear current generator 2 on the threshold unit 4, which opens the element And 5 in the presence of the enabling signal from the trigger 8, and the pulses produced by the generator 12 clock pulses, through the divider 13 pulses arrive at the counter 6 pulses.

As the current increases, the product demagnetizes, and at the moment of equality of the magnetic field induced in the coil 1, the coercive force Hci of the product 14, which corresponds to the value of the current IHCI (point in FI | .2a), the signal at the output of the fluxgate 9 decreases to zero and the trigger 8 tilts. The element 5 is closed and the supply of pulses from the generator of 12 clock pulses through the divider of 13 pulses, which (G reduces the number of pulses produced by the generator 12, is halved, counts 6 pulses). The quality of the pulses is proportional to the value of the coercive force Hci / 2. The current in the coil 1 continues to vary linearly to –122 (point r in Fig. 2a), while

0, magnetization reversal of the product 14 occurs and at the point g in Fig. 2a the product is magnetized to saturation, which corresponds to an increase in the output signal from the fluxgate 9 to the maximum. Under the influence of this signal

5 through the peak detector 10 and the differentiating circuit 11, the control unit 3 acts on the linear current generator 2. At this command, the current decreases again to zero (point d in Fig. 2a), and at the moment of transition

0 current through zero, the control unit 3 reverses the direction of the current of the linear current generator 2, simultaneously, through the threshold unit 4 and the element 5, pulses are fed to the pulse counter 6 from the clock generator 12 through a pulse divider 13. As the current in the coil 1 increases, demagnetization of the product 14 occurs again and at the moment of equality of the magnetic field of the coil 1 to the coercive force Hc2 of the product 14, which corresponds to the value of the current in. coil 11ns2 (e in fig. 2a), zero appears at the exit of the fluxgate 9, causing the flip-flop 8. to overturn. And 5 is closed and the flow is stopped

5 pulses from the generator 12 clock pulses per counter 6 pulses, while to the number of pulses recorded by the counter during the first count, proportional to Hci / 2 is added the number

0 pulses, proportional to the value UNCs2 / 2, and on the digital indicator 7 appears the value corresponding to the coercive force of the measured product 14,

five

Thus, a change in the coercive force of the product with two directions of the demagnetizing common current makes it possible to increase the measurement accuracy by automatically compensating for the effects of external extraneous magnetic fields.

Fig. 2a shows a diagram of the variation of the current generator current (graphs in Fig. 2a) for the product, the coercive force of which is two times less than the coercive force of the product, previously measured (plot 1 on fig.2a).

The magnetization of this product to saturation occurs at a lower current (point a in figure 2a), and then the current decreases to zero (point b in figure 2a) and the polarity changes. At point B, the first measurement of the coercive force occurs, and at point e, the second, the measured value of the coercive force appears on the digital indicator. Thus, the measurement time of the coercive force in the second case is practical and two times less compared to the first case: ti / tz c 2 (Fig. 2a), where tt is the measurement time of the larger coercive force, t2 is the measurement time of the smaller coercive force, t . when controlling the magnetization process and magnetization reversal of the product, depending on the magnitude of the coercive force, the strength of the product, and consequently, the value of the maximum saturation field, the control performance increases.

Fig. 2b shows the measurement of the coercive forces at points b and e, as well as at points a and e, respectively, which are also twice as large, with a fixed change in the magnetizing current and demagnetization of the products. The diagram shows that the measurement time of the coercive force of the product at points a and e in fig. 2b is almost equal to the measurement time of the coercive force of the product at points в and e in fig. 2b, which differ from each other by two times, i.e. in this case, there is practically no gain in time and an increase in the measurement performance.

Formulas for measurement Digital automatic coercimeter containing serially connected control unit, linear current generator, Helmholtz coil, serially connected ferrosonde, trigger, I element, pulse counter and digital indicator, as well as such a pulse generator and a threshold unit, with the second generator output linear current through the threshold unit is connected to the second input of the element I, which is the fact that, in order to increase the accuracy,

a pulse divider, a peak detector, and a differentiating circuit are additionally introduced into it, the clock pulse generator output being connected to the third input of the And element through the divider of 1-pulses,

and the output of the fluxgate through a series-connected peak detector and differentiating circuit is connected to the input of the control unit.

Claims (1)

Measurement formula A digital automatic coercimeter containing a control unit, a line current generator, a Helmholtz coil, a flux-gate, a trigger, an element And, a pulse counter and a digital indicator, as well as a clock generator and a threshold block, and the second output of the line current generator through the threshold the unit is connected to the second input of the element And, on the other hand, in order to increase accuracy, an impulse divider, a peak detector and a differentiating I have a circuit, and the output of the clock generator through the pulse divider is connected to the third input of the And element, and the output of the flux gate through the peak detector and the differentiating circuit connected in series is connected to the input of the control unit.