CN103970162B - The heater of a kind of cylindrical coaxial resonant cavity and temperature-controlled process thereof - Google Patents

Abstract

The invention discloses a heating device for a cylindrical coaxial resonant cavity and a temperature control method thereof. The device includes a control unit, a temperature acquisition unit, and a power heating unit. The method includes temperature acquisition, temperature comparison, temperature statistics, and temperature adjustment. steps. The invention controls the heating power by changing the current flowing through the drain and source of the MOSFET tube to meet the requirements of a controllable and uniform heating process, which can effectively reduce the influence of the working temperature on the resonance frequency and improve the accuracy of the wet density detection of the material .

Description

A heating device for a cylindrical coaxial resonant cavity and a temperature control method thereof

technical field

The invention relates to the field of heating devices, in particular to a heating device for a cylindrical coaxial resonant cavity and a temperature control method thereof.

Background technique

In the process of using the resonant cavity method to detect the wet density of materials, the stability of the resonant frequency is crucial to the test accuracy; and due to the thermal expansion effect of the cavity material, the size of the resonant cavity is related to the experimental temperature and the thermal expansion coefficient of the material. Therefore, the cavity resonant frequency of the resonator will change due to the difference between the working temperature and the reference temperature. Therefore, in order to ensure the test accuracy, it is necessary to heat the resonant cavity and keep the temperature constant, and avoid sudden cooling and sudden heating during the heating process to maintain a uniform and controllable heating process.

The existing heating control circuit usually uses the on-off action of PWM wave to control the heating process. When PWM wave is simply used to control the heating power, the heating circuit is heated at full power when the PWM wave is high, and the heat is large; when the PWM wave is low, it does not heat at all, and the inertia of the control process is large, and the heating temperature cannot be continuously and accurately controlled. Keep it even.

Therefore, how to obtain a controllable uniform heating process is a technical problem to be solved by those skilled in the art in order to reduce the influence of the working temperature on the resonance frequency and improve the test accuracy.

SUMMARY OF THE INVENTION The object of the present invention is to provide a heating device for a cylindrical coaxial resonant cavity and its temperature control method, by continuously changing the current flowing through the drain and source of the MOSFET tube to control the heating power to meet the controllable, Uniform heating process requirements.

In order to achieve the above object, the technical scheme adopted in the present invention is:

A heating device for a cylindrical coaxial resonant cavity, characterized in that: it includes a control unit, a temperature acquisition unit, and a power heating unit, and the temperature acquisition unit and the power heating unit are respectively connected to the control unit;

The temperature acquisition unit is arranged in a slot on the cylindrical coaxial resonant cavity, and is in close thermal contact with the cylindrical coaxial resonant cavity;

The control unit includes a control voltage generation subunit and a filter adjustment subunit, wherein the control voltage generation subunit is composed of a main control chip and a DA conversion chip connected to the main control chip, and the filter adjustment subunit is a filter circuit composed of an operational amplifier, The proportional integral circuit is composed, the signal output by the temperature acquisition unit is connected to the main control chip, and the main control chip controls the DA conversion chip to generate a control voltage signal according to the signal output by the temperature acquisition unit, and the control voltage signal generated by the DA conversion chip is connected to the filter The adjustment sub-unit is converted into a power control voltage signal and connected to the power heating unit after being filtered by the filter circuit in the filter adjustment sub-unit and converted by the proportional integral circuit in sequence;

The power heating unit includes two power MOSFET tubes, the two power MOSFET tubes are distributed on the top and bottom of the cylindrical coaxial resonant cavity, and are in close thermal contact with the cylindrical coaxial resonant cavity respectively, and the two power MOSFET tubes are respectively Receive the power control voltage signal output by the filter adjustment sub-unit in the control unit, and control the width of the induction channel of the two power MOSFET tubes by the power control voltage signal to adjust the current between the drain and the source, and complete the heating power size control.

The heating device for a cylindrical coaxial resonant cavity is characterized in that: the temperature acquisition unit adopts a high-precision digital temperature-sensing integrated circuit, and the output of the temperature acquisition unit is connected to the control unit for control through a serial bus. The main control chip of the voltage generation sub-unit, and the temperature acquisition unit is arranged in the slot on the cylindrical coaxial resonant cavity through the heat conduction pad.

The heating device for a cylindrical coaxial resonant cavity is characterized in that: the filter adjustment subunit is composed of a filter circuit composed of an operational amplifier and a proportional integral circuit, wherein:

The filter amplifier circuit includes an operational amplifier U1. The control voltage signal generated by the DA conversion chip is sequentially connected to the inverting input terminal of the operational amplifier U1 through the series resistor R1 and resistor R2. The capacitor C1 is grounded between the resistor R1 and the resistor R2. The operational amplifier The non-inverting input terminal of U1 is grounded, and a resistor R3 is connected between the inverting input terminal and the output terminal of the operational amplifier U1;

The proportional-integral circuit includes operational amplifiers U2 and U3. The output terminal of the operational amplifier U1 is connected to the inverting input terminal of the operational amplifier U2 through a resistor R4, and the output terminal of the operational amplifier U1 is also connected to the inverting input terminal of the operational amplifier U3 through a resistor R5. , the non-inverting input terminal of the operational amplifier U2 is grounded, the capacitor C2 is connected between the inverting input terminal and the output terminal of the operational amplifier U2, the non-inverting input terminal of the operational amplifier U3 is grounded, and the inverting input terminal and the output terminal of the operational amplifier U3 are connected The capacitor C3, the output terminal of the operational amplifier U2 are respectively connected to the power heating unit through the resistor R6, and the output terminal of the operational amplifier U3 is connected to the power heating unit through the resistor R7, so as to output two power control voltage signals to the power heating unit.

The heating device for a cylindrical coaxial resonant cavity is characterized in that: the power heating unit includes two power MOSFET tubes T1 and T2, and the two power MOSFET tubes T1 and T2 are respectively coated with thermally conductive silicone grease and The upper screw is in close contact with the top and bottom of the cylindrical coaxial resonant cavity. The sources of the two power MOSFETs T1 and T2 are respectively grounded, and the drains are respectively connected to the power supply VCC. The gate of one of the power MOSFETs T1 passes through the resistor R8 and the source are respectively connected to the power control voltage signal output by one of the proportional integral circuits in the filter adjustment subunit through the resistor R9, and the gate of the other power MOSFET T2 is respectively connected to the filter adjustment through the resistor R10 and the source through the resistor R11 The power control voltage signal output by another channel of the proportional integral circuit in the subunit.

A temperature control method for a cylindrical coaxial resonant cavity, characterized in that: comprising the following steps:

(1), temperature acquisition step: measure the temperature of the heated cylindrical coaxial resonant cavity through the temperature acquisition unit;

(2) Temperature comparison step: compare the difference between the temperature of the cylindrical coaxial resonant cavity measured by the temperature acquisition unit and the target temperature and the temperature difference between two adjacent acquisitions through the main control chip in the control unit;

(3) Temperature statistics step: through the main control chip in the control unit, the difference between the temperature of the cylindrical coaxial resonant cavity collected each time and the target temperature is accumulated;

(4) Temperature adjustment step: when the temperature of the cylindrical coaxial resonant cavity is lower than the target temperature, the control unit calculates and generates a power control voltage signal to adjust the heating power.

Beneficial effects of the present invention:

The invention provides a heating circuit for a cylindrical coaxial resonant cavity and its temperature control method, which controls the heating power by changing the current flowing through the drain and source of the MOSFET tube to meet the controllable and uniform heating It can effectively reduce the influence of working temperature on resonance frequency and improve the accuracy of material wet density detection.

Description of drawings

FIG. 1 is a schematic block diagram of a heating circuit of the present invention.

FIG. 2 is a schematic block diagram of the control voltage generating subunit of the present invention.

FIG. 3 is a schematic block diagram of the filter adjustment subunit of the present invention.

Fig. 4 is a schematic block diagram of the power heating unit of the present invention.

Fig. 5 is a schematic diagram of the installation positions of the temperature acquisition unit and the power heating unit of the present invention.

Fig. 6 is a flow chart of the temperature control method of the present invention.

detailed description

As shown in Figures 1-5, a heating device for a cylindrical coaxial resonant cavity includes a control unit 102, a temperature acquisition unit 101, and a power heating unit 103, and the temperature acquisition unit 101 and the power heating unit 103 are respectively connected with the control unit unit 102 connection;

The temperature acquisition unit 101 is arranged in a slot on the cylindrical coaxial resonant cavity, and is in close thermal contact with the cylindrical coaxial resonant cavity;

The control unit 102 includes a control voltage generation subunit 201 and a filter adjustment subunit 202, wherein the control voltage generation subunit 201 is composed of a main control chip 301 and a DA conversion chip 302 connected to the main control chip 301, and the filter adjustment subunit 202 is composed of an operation A filter circuit composed of an amplifier and a proportional integral circuit are composed. The signal output by the temperature acquisition unit 101 is connected to the main control chip 301, and the main control chip 301 controls the DA conversion chip 302 to generate a control voltage signal according to the signal output by the temperature acquisition unit 101, and the DA conversion The control voltage signal generated by the chip 302 is connected to the filter adjustment subunit 202, and after being filtered by the filter circuit in the filter adjustment subunit 202 and transformed by the proportional integral circuit in turn, it is converted into a power control voltage signal and connected to the power heating unit 103;

The power heating unit 103 includes two power MOSFET tubes, the two power MOSFET tubes are distributed on the top and bottom of the cylindrical coaxial resonant cavity, and are in close thermal contact with the cylindrical coaxial resonant cavity respectively, and the two power MOSFET tubes respectively receive The power control voltage signal output by the filter adjustment sub-unit 202 in the control unit 102 controls the width of the induced channel of the two power MOSFET tubes by the power control voltage signal to adjust the current between the drain and the source to complete the heating Power size control.

The temperature acquisition unit 101 adopts a high-precision digital temperature-sensing integrated circuit. The output of the temperature acquisition unit 101 is connected to the main control chip of the control voltage generation subunit 201 in the control unit 102 through a serial bus, and the temperature acquisition unit 101 is set through a thermal pad. Slotted on the cylindrical coaxial resonant cavity.

The filter adjustment subunit 202 is composed of a filter circuit composed of an operational amplifier and a proportional-integral circuit, wherein:

The filter amplifier circuit includes an operational amplifier U1. The control voltage signal generated by the DA conversion chip is sequentially connected to the inverting input terminal of the operational amplifier U1 through the series resistor R1 and resistor R2. The capacitor C1 is grounded between the resistor R1 and the resistor R2. The operational amplifier The non-inverting input terminal of U1 is grounded, and a resistor R3 is connected between the inverting input terminal and the output terminal of the operational amplifier U1;

The proportional-integral circuit includes operational amplifiers U2 and U3. The output terminal of the operational amplifier U1 is connected to the inverting input terminal of the operational amplifier U2 through a resistor R4, and the output terminal of the operational amplifier U1 is also connected to the inverting input terminal of the operational amplifier U3 through a resistor R5. , the non-inverting input terminal of the operational amplifier U2 is grounded, the capacitor C2 is connected between the inverting input terminal and the output terminal of the operational amplifier U2, the non-inverting input terminal of the operational amplifier U3 is grounded, and the inverting input terminal and the output terminal of the operational amplifier U3 are connected The capacitor C3, the output terminal of the operational amplifier U2 are respectively connected to the power heating unit through the resistor R6, and the output terminal of the operational amplifier U3 is connected to the power heating unit through the resistor R7, so as to output two power control voltage signals to the power heating unit.

The power heating unit 103 includes two power MOSFET tubes T1 and T2. The two power MOSFET tubes T1 and T2 are respectively in close contact with the top and bottom of the cylindrical coaxial resonant cavity by applying heat-conducting silicone grease and screws. The two power MOSFET tubes The sources of the tubes T1 and T2 are respectively grounded, and the drains are respectively connected to the power supply VCC. The gate of one of the power MOSFET tubes T1 is respectively connected to one of the output circuits of the proportional integral circuit in the filter adjustment subunit through the resistor R8 and the source through the resistor R9. The power control voltage signal of the other power MOSFET tube T2 is respectively connected to the power control voltage signal output by the proportional integral circuit in the filter adjustment sub-unit through the resistor R10 and the source through the resistor R11.

As shown in Figure 6, a temperature control method of a cylindrical coaxial resonant cavity comprises the following steps:

(1), temperature acquisition step: measure the temperature of the heated cylindrical coaxial resonant cavity through the temperature acquisition unit;

(2) Temperature comparison step: compare the difference between the temperature of the cylindrical coaxial resonant cavity measured by the temperature acquisition unit and the target temperature and the temperature difference between two adjacent acquisitions through the main control chip in the control unit;

(3) Temperature statistics step: through the main control chip in the control unit, the difference between the temperature of the cylindrical coaxial resonant cavity collected each time and the target temperature is accumulated;

(4) Temperature adjustment step: when the temperature of the cylindrical coaxial resonant cavity is lower than the target temperature, the control unit calculates and generates a power control voltage signal to adjust the heating power.

Referring to FIG. 1 , the heating circuit of the present invention mainly includes a temperature acquisition unit 101 , a control unit 102 and a power heating unit 103 . The control unit 102 includes a control voltage generation subunit 201 and a filter adjustment subunit 202, which are connected to the temperature acquisition unit through a serial bus, receive the collected temperature value of the resonant cavity, and the control voltage generation subunit 201 generates a control voltage through calculation And through the filter adjustment sub-unit 202, the control voltage is adjusted by filter integration and output to the power heating unit 103 to complete the adjustment of the heating power.

Referring to FIG. 2 , the control voltage generation subunit 201 of the present invention is mainly composed of a main control chip 301 and a DA conversion chip 302 . The main control chip 301 receives the temperature value collected by the temperature acquisition unit 101 through the serial bus, calculates and outputs it to control the DA conversion chip 302, and the DA conversion chip 302 generates a control voltage signal.

Referring to FIG. 3 , the generated control voltage signal is connected to the filter adjustment subunit 202 , and after filtering, it is integrally adjusted to be a control voltage that can control the heating power of the MOSFET tube in the power heating unit 103 .

4, the power heating unit 103 of the present invention includes two power MOSFET tubes, and the power heating control voltage generated by the control unit 102 is connected to the gate of the power MOSFET tube, so that the width of the induction channel of the MOSFET tube can be adjusted, and then the MOSFET tube can be adjusted. The current flowing through the drain and source of the tube can complete the control of the heating power of the MOSFET tube.

In conjunction with Figure 5, the temperature acquisition unit 101 uses a high-precision digital temperature-sensing integrated circuit, which is in close contact with the resonant cavity through a thermal pad in the slot at the bottom of the resonant cavity, and is used to collect the temperature of the resonant cavity; in order to ensure that the resonant cavity The body is heated evenly, and two power MOSFET tubes are distributed in the upper and lower parts of the resonant cavity. They are in close contact with the resonant cavity by applying heat-conducting silicone grease and attaching screws.

Referring to FIG. 6 , the temperature control method in the present invention is mainly divided into four steps: a temperature collection step, a temperature comparison step, a temperature statistics step and a temperature adjustment step. The temperature acquisition step uses the temperature acquisition unit 101 to measure the temperature of the heated resonant cavity; the temperature comparison step is to compare the resonant cavity temperature measured by the temperature acquisition unit 101 with the main control chip 301 in the control unit 102 The difference between the target temperature and the temperature difference between two adjacent acquisitions; the temperature statistics step is to accumulate the difference between the resonant cavity temperature and the target temperature collected each time; the temperature adjustment step is the same as the above three steps. When the temperature of the cavity is lower than the target temperature, close to the target temperature or slightly above the target temperature, the control unit calculates and generates a power control voltage signal to adjust the heating power, and performs full-power, half-power, and micro-power heating on the resonant cavity And without heating.

Claims (2)

1. the heater of a cylindrical coaxial resonant cavity, it is characterised in that: include control unit, temperature acquisition list Unit, power heating unit, described temperature collecting cell and power heating unit are connected with control unit respectively；Described temperature is adopted Collection unit is located on cylindrical coaxial resonant cavity in fluting, and thermal conductive contact tight with cylindrical coaxial resonant cavity；

Described control unit includes controlling voltage generating subunit, filtering adjusts subelement, wherein controls voltage generating subunit Being made up of the DA conversion chip of main control chip, access main control chip, filtering adjusts the filtering that subelement is made up of operational amplifier Circuit, proportional integral circuit are constituted, and the signal of described temperature collecting cell output accesses main control chip, and main control chip is according to temperature The signal of collecting unit output, controls DA conversion chip and produces control voltage signal, the control voltage letter that DA conversion chip produces Number accessing filtering adjusts subelement, sequentially passes through filtering and adjusts filter circuit filtering, proportional integral circuit ratio in subelement and amass After dividing conversion, it is transformed to power control voltage signal access power heating unit；

Described power heating unit includes that two power MOSFET tubes, two power MOSFET tubes are distributed in cylindrical coaxial resonance Cavity top and bottom, and thermal conductive contact tight with cylindrical coaxial resonant cavity respectively, two power MOSFET tubes connect respectively Receive filtering in control unit and adjust the power control voltage signal of subelement output, power control voltage signal control two merits Rate MOSFET pipe is inducted the width of raceway groove, to adjust the size of electric current between drain electrode and source electrode, completes heating power size Control；

Described temperature collecting cell uses high-precision digital temperature-sensitive integrated circuit, and temperature collecting cell output is total by serial Line Access Control unit controls the main control chip of voltage generating subunit, and temperature collecting cell is arranged on circle by heat conductive pad On cylindrical coaxial resonant cavity in fluting；

Filter circuit, proportional integral circuit that described filtering adjustment subelement is made up of operational amplifier are constituted, wherein: filtering Amplifying circuit includes operational amplifier U1, and the control voltage signal that DA conversion chip produces sequentially passes through the resistance R1 of series connection, electricity Resistance R2 accesses the inverting input of operational amplifier U1, by electric capacity C1 ground connection between resistance R1 and resistance R2, operational amplifier The in-phase input end ground connection of U1, is connected to resistance R3 between inverting input and the output of operational amplifier U1；Proportional integral electricity Road includes operational amplifier U2, U3, and the output of operational amplifier U1 accesses the anti-phase defeated of operational amplifier U2 by resistance R4 Entering end, the output of operational amplifier U1 accesses the inverting input of operational amplifier U3, operational amplifier also by resistance R5 The in-phase input end ground connection of U2, accesses electric capacity C2, operational amplifier between inverting input and the output of operational amplifier U2 The in-phase input end ground connection of U3, accesses electric capacity C3, operational amplifier between inverting input and the output of operational amplifier U3 The output of U2 is respectively connected to power heating unit by the output of resistance R6, operational amplifier U3 by resistance R7, with to Power heating unit output two-way power control voltage signal；

Described power heating unit includes two power MOSFET tubes T1, T2, and two power MOSFET tubes T1, T2 are respectively by being coated with Smear heat-conducting silicone grease screwing and cylindrical coaxial resonant cavity top, the corresponding close contact in bottom, two power MOSFET tubes The source electrode of T1, T2 ground connection respectively, drain electrode is respectively connected to power supply VCC, and the grid of one of them power MOSFET tube T1 passes through resistance R8, source electrode are respectively connected to filtering by resistance R9 and adjust the power control electricity of a proportional integral circuit wherein road output in subelement Pressure signal, the grid of another power MOSFET tube T2 is respectively connected to filtering by resistance R10, source electrode by resistance R11 and adjusts The power control voltage signal of another road of proportional integral circuit output in subelement.

2. based on a temperature-controlled process for the heater of cylindrical coaxial resonant cavity described in claim 1, its feature It is: comprise the following steps:

(1), temperature acquisition step: measured the temperature of heated cylindrical coaxial resonant cavity by temperature collecting cell；

(2), temperature comparison step: by the cylindrical coaxial measured by main control chip C.T collecting unit in control unit Resonant cavity temperature and the difference of target temperature and the temperature gap of adjacent twice collection；

(3), temperature statistics step: by main control chip in control unit to each cylindrical coaxial resonant cavity temperature gathered Add up with the difference of target temperature；

(4), temperature adjustment steps: when the temperature of this cylindrical coaxial resonant cavity is less than this target temperature, single by controlling Unit calculates generation power control voltage signal and adjusts the size of heating power.