RU189683U1 - A device for conducting current annealing of microwires with remote temperature control - Google Patents

Abstract

The utility model refers to the technology of building sensors based on amorphous microwires and a magnetoimpedance effect. The purpose of creating a utility model was 1. possibility of remote control and temperature measurement; 2. the absence of additional temperature gradients during measurements. The goal is achieved by the fact that a new principle of measuring the temperature of a microwire has been applied in the design, and equipment has been proposed for measuring. The temperature is directly measured on the heating platform of the witness sample, the temperature of which is set equal to the temperature of the sample under study using a control unit and a bridge circuit. The sensitivity of the operational amplifier and the inertia of the heating platform make it possible to obtain a temperature setting on the sample by a witness with an accuracy of up to 5 ° С in the temperature range up to 270 ° С. 3 il.

Description

The invention relates to the technology of building sensors based on amorphous microwires and a magnetoimpedance effect.

A device for remote temperature control when conducting current annealing or other heat treatment (IR heating, heating in a furnace) of the microwire allows you to remotely control its temperature in cases of working with excessively small samples.

The design most similar to the proposed one was published on May 20, 1995, in patent RU 2 035 705 C1: SINGER METHOD A.M. TEMPERATURE MEASUREMENTS.

The disadvantages of the patent-analogue is narrowly specialized application and relatively complex design.

The difference is that the two resistive bridges are combined into one common, and the amplified signal from the amplifier (comparator) goes not to the generator, but to the control element of the platform heater, where the temperature is monitored.

It is worth noting that in patent RU 2 035 705 C1 the temperature is calculated based on the differences in dissipated power, whereas, in the present embodiment, it is proposed to equalize the temperatures of the samples by adding additional power and to directly measure the temperature on the heating platform.

The technical result consists in the implementation of remote control of the sample temperature without directly installing a temperature sensor on the sample to be measured during temperature processing or current annealing.

The technical result is achieved as follows: a device for conducting current annealing of microwires with remote control of temperature, containing a power source, a thermal sensor with a display device, a control unit with a substrate for the sample being measured and a witness sample with a heating platform, which is located on a heating platform with a sample-witness, a sample-witness, and an annealing sample are included in a bridge circuit, the balance of which controls the precision control unit amplifier to which the heating platform is connected.

Figure 1 shows the general block diagram of the device. In this case, the temperature is controlled not on the sample under test, but on the sample witness. The witness sample is identical in composition, dimensions to other properties of the controlled sample and has good thermal contact with the heating platform. The test sample is heated by the current flowing through it, and the sample is a witness heated by the heating platform and the current passing through it. A temperature sensor is installed on the heating platform, the platform temperature is automatically equalized to the sample temperature using a control unit and a bridge circuit. The utility model is illustrated by drawings, where in FIG. 1, FIG. 2, FIG. 3 depicted:

1 - power supply;

2 - control unit;

3 - measured sample;

4 - heating platform with a sample witness;

5 - temperature indicator;

6 - adjustable current limiter;

7 - bridge balancer;

8 - temperature control unit;

9 - microwire (sample witness);

10 - thermocouple (thermal sensor);

11 - heating elements of the platform;

Description of the device. The power source (1), a stand-alone standardized device (B5-8 or similar), provides power with a rated voltage of 15 V and a maximum current of 1A. The control unit (2) sets the current for the measurement or annealing, compares the temperature of the sample being measured (3) and the sample of the witness (4) by changing their resistance and turns on the heater of the heating platform for temperature equalization, the current temperature is displayed on the temperature indicator (5).

In FIG. 2 shows the block diagram of the control unit and its connection to the remaining blocks. The substrate of the sample to be measured and the heating platform with the sample-witness are integral removable parts of the control unit. The measured sample (3), the sample witness (4) and the bridge resistors in the control unit are included in the overall bridge circuit. Using the regulator (6), the measurement mode or the current value for current annealing is selected (depending on the position of the regulator knob). Before work the regulator (7) balances the bridge. The temperature control unit (8) with the help of a precision operational amplifier monitors the temperature change of the sample being measured and turns on the heater of the heating platform of the witness sample if its temperature is less than the temperature of the sample being measured. The temperature control unit (8), which is part of the control unit (2), consists of a precision operational amplifier (OU), a linear voltage regulator and a power transistor control heater. The linear regulator feeds the operational amplifier with a voltage of 6 V. The direct and inverting inputs of the operational amplifier are connected to the measuring bridge. When working with materials with a positive temperature coefficient of resistance, the inverting input is connected to the bridge diagonal from the side of the witness sample, and the non-inverting input from the side of the sample under study. When working with materials with a negative temperature coefficient of resistance, it is necessary to inversely turn on the operational amplifier. The output of the operational amplifier is connected to the gate of the field-effect transistor, the source of the transistor is connected to the common wire, and its drain to the platform heater.

In FIG. 3 shows the device of the heating platform and its connection. The heating elements are divided into two branches to compensate for the induced magnetic field at the installation site of the microwire and are evenly distributed over the platform for its uniform heating. Rated power of the heater of the heating platform is 8 watts. A thermocouple is installed on the platform in the immediate vicinity of the microwire of the sample-witness. To ensure the necessary thermal contact of the microwire of the sample-witness, it is installed on the platform using heat-conducting paste, and the microwire is closed with a kapton tape on top. The microwire of the sample witness and the sample to be measured are selected from the same batch, their length and diameter are identical. After the installation of microwires and before the experiment, the equality of resistance of both samples is controlled, the deviation should not exceed 5%.

Thus, the following distinctive features of the device for conducting current annealing of microwires with remote temperature control can be noted:

- direct temperature measurement takes place on a heating platform with a sample-witness;

- the temperature of the witness sample is automatically set equal to the temperature of the sample being measured;

- minimized temperature gradient in the measured sample due to the lack of physical contact of the microwire with a temperature sensor (thermocouple).

- bridge circuit with the use of a precision operational amplifier in the control circuit and low heat capacity of the heating platform, which allows to obtain the error of setting the temperature not more than 5 ° С in the temperature range up to 270 ° С.

The use of these distinctive features to accomplish the goal previously unknown to the authors.

Example 1

After connecting the samples using an external microvoltmeter, the bridge is balanced. When balancing limit the current passing through the bridge of 0.5 mA, during balancing through the measured sample air is blown. The execution time of the balancing should not exceed 5 seconds. After performing the balancing, the current for annealing will be switched on, which also flows through both microwires (measured sample and witness sample) and heats them, while the measured microwire heats up much faster than the witness's sample. Thus, an imbalance of the resistive bridge occurs, which is why an operational amplifier in the temperature control unit connected to the motu switches on the platform heater and turns it off when the temperature of the monitored sample and the witness's sample coincides. As a result, the heat sink of the temperature sensor is automatically compensated by the input power to the heating platform.

Claims (1)

A device for conducting current annealing of microwires with remote control of temperature, containing a thermal sensor with a display device, a control unit with a substrate for the sample being measured and a witness sample with a heating platform, powered by a stabilized DC network, characterized in that the thermal sensor for temperature control is located on the heating a platform with a witness sample, a witness sample and an annealing sample are included in a bridge circuit, the balance of which is controlled by a precision block amplifier and the control that is connected to a heating platform with a model witness.

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