SU134329A1 - Device for determining the Curie point of ferromagnetic materials - Google Patents

Description

The described device for determining the Curie point of ferromagnetic materials is based on the use of a block of two sensors, the input of which is connected to a sinusoidal voltage generator of increased frequency, and the output to an electronic indicator unit. One of the sensors included in the block is measuring, and the other is compensation. Each sensor consists of a solenoid, the inductance of which depends on the magnetic properties of the sample introduced into it, and from an active co-current connected in series with the solenoid.

For express determination of the Curie point in the proposed device, the indicator unit is made on two channels connected to the active resistances of the sensors. Each of the channels contains a differentiating chain that generates pulses into monoments of the transition of a sinusoidal voltage through zero, and an anti-coincidence block that registers the time shift (in phase) of the pulses of the indicated channels. If the pulses do not match, a signal is sent to the output unit, which activates the signal lamp and the temperature recorder.

To increase the steepness of the fronts of the compared sinusoidal voltages at the input of the differentiating chains, limiter amplifiers are included.

FIG. 1 shows a circuit diagram of the device proposed; in fig. 2 and 3, respectively, measuring and compensating sensors.

The device includes: a generator unit /, a sensor unit II, an indicator unit ///, an anti-coincidence unit IV, an output unit V and a power supply unit VI.

No. 134329-2 Sensors are powered by a variable voltage with a frequency of about 1000 Hz from a generator assembled on lamps L, L, using a push-pull circuit with feedback circuits.

The sensor unit // includes a measuring sensor consisting of a Ly solenoid and a resistance Ri, and a compensation sensor consisting of an LZ solenoid and a resistance RZ. Inside the solenoid LI of the measuring sensor (Fig. 2) are placed a tubular electric heater 1 and a coil 3 separated from it by a refractory coating 2 with running water, which protects the solenoid winding from heating. The test sample 4 is introduced into the heater, the temperature of which is measured by a thermocouple 5. A copper cylinder 6 is introduced inside the solenoid LZ compensation sensor (Fig. 3) to compensate for the initial phase shift in both sensors.

The settings taken from the sensors through the phase-shifting RC chains are fed to the inputs of two-stage amplifiers on lamps L, L and L, / 7b. Phase rotation chips are used when setting the operation mode before starting measurements. The output stages of the amplifiers operate with a cut-off, so that the shape of the voltages at the anodes of the L and L lamps is close to rectangular. The output signals of the amplifiers are differentiated.-Chains with a constant time of 15 microseconds and are fed to the inputs of two one-way multivibrators made according to the cathode coupling scheme respectively on lamps channel - 16 microseconds.

At the beginning of work at a temperature below the Curie temperature, the narrow pulse of the measuring channel is combined in time with the pulse of the compensation channel.

The phase shift of the current in the measuring channel with a sharp change in the magnetic permeability of the sample shifts in time a narrow pulse relatively wide, which (leads to the triggering of subsequent stages.

To indicate the moment of pulse divergence, there is an anti-coincidence circuit on lambs n, / 7i2, lostroenp on the principle of a differential amplifier with asymmetrical bias. Lamp L is normal. Positive pulses are applied to its grid from a portion of the anode load of the Liu lamp of the compensation channel multivibrator. The la lamp is normally blocked from the cathode side by the current of the lamp 11 and positive pulses are fed to its grid from the multi-vibrator of the measuring channel. If the BO time does not match the input impulses of the anti-coincidence circuit at the anode of the / 7i2 lamp, a negative impulse occurs, which triggers the output block. The capacitance C delays the output impulse of the anti-coincidence circuit, which contributes to a more precise response of the output -block.

The output unit is designed as a multivibrator on lamps Lc and y7i5. A high-speed relay R. is turned on to the anode circuit of the lamp / 7i5, a normally closed lo control grid, and the high-speed relay R. L. In this case, the relay P is activated and its normally open IP contacts switch on the signal lamp Liu. A second pair of 2P relay P contacts is included in the temperature recorder control circuit.

Subject invention

Claims (2)

1. A device for determining the Curie point of ferromagnetic materials, containing a block of sensors whose input is connected to a sinusoidal voltage-frequency generator, and the output to an electronic indicator unit, characterized in that in order to accelerate the measurement process, the indicated indicator unit has two caaals connected to active resistances in the sensor circuit and containing each differentiating chain, producing pulses at the moments of a sinusoidal voltage crossing zero, and an anti-coincidence unit that registers the shift in time (in phase) of the pulses of the indicated channels so that when the pulses do not coincide, a signal is sent to the output unit. 2. The device according to claim 1, excluding that the limiter amplifiers are included at the input of the differentiating chains to increase the steepness of the fronts of the compared sinusoidal voltages. YuOOgi,