CN213688720U

CN213688720U - Temperature measuring device for numerical control machine tool

Info

Publication number: CN213688720U
Application number: CN202021917250.9U
Authority: CN
Inventors: 罗堪; 蔡聪; 李建兴; 杨睿宁; 沈亮
Original assignee: Saiyang Electromechanical Co ltd
Current assignee: Saiyang Electromechanical Co ltd
Priority date: 2020-09-05
Filing date: 2020-09-05
Publication date: 2021-07-13
Anticipated expiration: 2030-09-05

Abstract

The utility model discloses a temperature measuring device for a numerical control machine tool, which comprises an external interface, a power module, a control unit and an acquisition unit; the external interface is connected with an external power supply line, and the power supply line is connected with the power supply module; the power supply module is respectively connected with the control unit and the acquisition unit; the control unit comprises an RS485 chip, a dial switch and an MCU, wherein the dial switch is connected with the MCU, and the RS485 chip is connected with the MCU; the external interface is connected with a communication line, and the communication line is connected with an RS485 chip; the acquisition unit comprises an analog-to-digital converter, a constant current source, a platinum thermal resistor, a reference resistor and a filter circuit, wherein the constant current source is integrated in the analog-to-digital converter; the platinum thermal resistor is connected to the constant current source, and the reference resistor is connected with the platinum thermal resistor; the platinum thermal resistor and the reference resistor are respectively connected with the filter circuit; the filter circuit is connected with the input port of the analog-to-digital converter and is used for filtering high-frequency clutter on the voltage input into the analog-to-digital converter; the analog-to-digital converter is connected with the MCU. The utility model discloses measurement accuracy is high.

Description

Temperature measuring device for numerical control machine tool

Technical Field

The utility model relates to a temperature measurement field especially relates to a temperature measuring device for digit control machine tool.

Background

With the improvement of productivity, numerically controlled machine tools are applied more and more widely in factories and become main machining equipment. The numerical control machine tool belongs to precision machining equipment, and the influence of temperature to its machining precision is comparatively obvious. In order to maintain the accuracy of the machine tool, the temperature of the machine tool during operation must be monitored in real time.

The contact type temperature measuring methods commonly used in industry include thermocouple and thermal resistance temperature measurement. The temperature measurement of the thermal resistor is to measure the temperature according to the rule that the resistance of the conductor changes along with the temperature, and the most common temperature measurement is the temperature measurement of the platinum thermal resistor. The platinum thermal resistance temperature measurement is divided into two-wire system, three-wire system and four-wire system according to different schemes. The error of the two-wire system is partially from the lead wire resistor, and the longer the lead wire is, the larger the resistance value is, and the larger the error is. The influence of lead wire resistance can be eliminated theoretically in a three-wire system and a four-wire system, but the premise is that the resistance value of each lead wire is completely consistent, and the larger the difference value between the lead wire resistances is, the larger the final measurement error is.

At present, common platinum thermal resistance measuring circuits on the market generally measure multi-path platinum thermal resistance, an external constant current source mode is basically adopted, and the circuit structure is complex. The number of platinum thermistors required may vary from machine to machine. If a circuit for multi-path measurement is adopted, the method is not only not applicable to all machine tools, but also can cause waste and increase the manufacturing cost. Meanwhile, if the multiple platinum thermistors are connected into the same measuring device, the leads of some platinum thermistors are long, and are easily interfered by the outside, so that the measuring result is inaccurate.

Disclosure of Invention

The utility model discloses to prior art's not enough, provide a temperature measuring device for digit control machine tool that the circuit is simple, the interference killing feature is strong, measurement accuracy is high.

The utility model discloses a technical goal is realized to following technical scheme.

The improvement of a temperature measuring device for a numerical control machine tool is that: the device comprises an external interface, a power supply module, a control unit and an acquisition unit; the external interface is connected with an external power supply line, and the power supply line is connected with a power supply module; the power supply module is respectively connected with the control unit and the acquisition unit; the control unit comprises an RS485 chip, a dial switch and an MCU, wherein the dial switch is connected with the MCU, and the RS485 chip is connected with the MCU; the external interface is connected with an external communication line, and the communication line is connected with the RS485 chip; the acquisition unit comprises an analog-to-digital converter, a constant current source, a platinum thermal resistor, a reference resistor and a filter circuit, wherein the constant current source is integrated in the analog-to-digital converter; the platinum thermal resistor is connected to a constant current source, and the reference resistor is connected with the platinum thermal resistor; the platinum thermal resistor and the reference resistor are respectively connected with the filter circuit; the filter circuit is connected with an input port of the analog-to-digital converter and is used for filtering high-frequency clutter on the voltage input into the analog-to-digital converter; the analog-to-digital converter is connected with the MCU; the current of the constant current source flows through a voltage signal generated by the platinum thermal resistor and is input to a differential input port of the analog-to-digital converter, and the voltage signal generated by the current flowing through the reference resistor is used as an external reference voltage of the analog-to-digital converter.

Preferably, the MCU is an STM32F030C8T6 singlechip.

Preferably, the analog-to-digital converter adopts an AD7793 chip, two matched constant current sources are integrated in the analog-to-digital converter, and the platinum thermal resistor is PT100 or PT1000 of a three-wire system.

Compared with the prior art, the utility model, following positive effect has: the utility model discloses circuit structure is simple, and it adopts RS485 bus and external communication, and single device platinum resistance only all the way, can shorten platinum resistance's lead wire length, and the length of extension RS485 bus uses, and the interference killing feature is stronger, also can reduce the error that platinum resistance lead wire resistance mismatch brought. Meanwhile, the RS485 bus is adopted for communicating with the outside, and the dial switch is arranged for coding of the device, so that the temperature measuring devices can be conveniently connected in parallel for use. The utility model discloses a two way constant current source that match each other of adc self-contained are measured, and adopt the platinum resistance of three-wire system as temperature sensor, still establish ties reference resistance and platinum resistance, and the voltage signal who produces when passing through reference resistance with the current is as the outside reference voltage of adc, can effectively reduce the constant current source temperature and float and the measuring error that the platinum resistance lead wire brought. Meanwhile, a filter circuit is added in front of the differential signal input port and the reference voltage input port, so that the final measurement result is more stable.

Drawings

Fig. 1 is a schematic structural diagram of the present invention.

Fig. 2 is a circuit diagram of the middle collecting unit of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by a person of ordinary skill in the art without creative efforts belong to the protection scope of the present invention.

Fig. 1 shows a temperature measuring device for a numerical control machine tool, which comprises an external interface 1, a power module 2, a control unit 3 and an acquisition unit 7; the external interface 1 is connected with an external power supply line, and the power supply line is connected with the power supply module 2; the power module 2 is respectively connected with the control unit 3 and the acquisition unit 7. The power module 2 is used for providing the electric energy needed by the acquisition unit 7 and the control unit 3.

The control unit 3 comprises an RS485 chip 4, a dial switch 5 and an MCU6, wherein the dial switch 5 is used for coding in the embodiment, the RS485 chip 4 is used for converting the communication level between the MCU6 and the outside, the dial switch 5 is connected with the MCU6, and the RS485 chip 4 is connected with the MCU 6; external interface 1 inserts the external communication line, and the communication line links to each other with RS485 chip 4, and in this embodiment, MCU 6's model is STM32F030C8T6 singlechip.

The acquisition unit 7 comprises an analog-to-digital converter 8, a constant current source 9, a platinum thermal resistor 10, a reference resistor 11 and a filter circuit 12, wherein the constant current source 9 is integrated in the analog-to-digital converter 8 and can provide two paths of mutually matched constant current sources; the platinum thermal resistor 10 is connected to the constant current source 9, and the reference resistor 11 is connected with the platinum thermal resistor 10; the platinum thermal resistor 10 and the reference resistor 11 are respectively connected with the filter circuit 12; the filter circuit 12 is connected with the input port of the analog-to-digital converter 8 and is used for filtering high-frequency noise waves on the voltage input into the analog-to-digital converter 8; the analog-to-digital converter 8 is connected with the MCU 6; a voltage signal generated by the current of the constant current source 9 flowing through the platinum thermal resistor 10 is input to a differential input port of the analog-to-digital converter 8, and a voltage signal generated by the current flowing through the reference resistor 11 is used as an external reference voltage of the analog-to-digital converter 8. In this embodiment, the analog-to-digital converter 8 is an AD7793 chip, two matched constant current sources 9 are integrated therein, and the platinum thermistor 10 is a three-wire PT100 or PT 1000.

FIG. 2 is a circuit diagram of the acquisition unit 7, RTD is platinum thermistor 10, RL1, RL2 and RL3 are lead resistances of three-wire platinum thermistor, R_REFIs a reference resistor 11. R1, R2, C1, C2 and C3 form a low-pass RC filter for differential signals, which is used to filter the differential voltage signals input to the analog-to-digital converter 8. And the low-pass RC filter consisting of R3 and C4 is used for filtering the reference voltage signal input into the analog-to-digital converter 8. Two mutually matched constant current sources 9 of the analog-to-digital converter 8 are respectively input into the RL1 and the RL2, so that the measurement errors caused by the RL1 and the RL2 can be eliminated, and a voltage signal generated by the current of the IOUT1 flowing through the RTD is input into a differential input port of the analog-to-digital converter 8 after passing through the filter circuit 12. Two paths of current are converged on RL3 and then pass through R_REFFlows into the power ground and flows through R_REFThe voltage signal generated during the measurement is input to the external reference voltage port of the analog-to-digital converter 8 after passing through the filter circuit 12, and is used as the external reference voltage of the analog-to-digital converter 8, so that the measurement error caused by the temperature drift of the constant current source 9 can be basically eliminated. Meanwhile, the two matched constant current sources 9 can be exchanged inside the analog-to-digital converter 8, so that the measurement error caused by the mismatch of the constant current sources 9 can be eliminated.

In the description herein, references to the description of "one embodiment," "an example," "a specific example," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

The preferred embodiments of the present invention disclosed above are intended only to help illustrate the present invention. The preferred embodiments are not exhaustive and do not limit the invention to the precise embodiments disclosed. Obviously, many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, to thereby enable others skilled in the art to best understand the invention for and utilize the invention. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A temperature measuring device for digit control machine tool which characterized in that: comprises an external interface (1), a power module (2), a control unit (3) and a collection unit (7); the external interface (1) is connected with an external power supply line, and the power supply line is connected with the power supply module (2); the power module (2) is respectively connected with the control unit (3) and the acquisition unit (7);

the control unit (3) comprises an RS485 chip (4), a dial switch (5) and an MCU (6), wherein the dial switch (5) is connected with the MCU (6), and the RS485 chip (4) is connected with the MCU (6); the external interface (1) is connected with an external communication line, and the communication line is connected with the RS485 chip (4);

the acquisition unit (7) comprises an analog-to-digital converter (8), a constant current source (9), a platinum thermal resistor (10), a reference resistor (11) and a filter circuit (12), wherein the constant current source (9) is integrated in the analog-to-digital converter (8); the platinum thermal resistor (10) is connected to a constant current source (9), and the reference resistor (11) is connected with the platinum thermal resistor (10); the platinum thermal resistor (10) and the reference resistor (11) are respectively connected with the filter circuit (12); the filter circuit (12) is connected with an input port of the analog-to-digital converter (8) and is used for filtering high-frequency clutter on the voltage input into the analog-to-digital converter (8); the analog-to-digital converter (8) is connected with the MCU (6); the voltage signal generated by the current of the constant current source (9) flowing through the platinum thermal resistor (10) is input to the differential input port of the analog-digital converter (8), and the voltage signal generated by the current flowing through the reference resistor (11) is used as the external reference voltage of the analog-digital converter (8).

2. A temperature measuring apparatus for a numerical control machine tool according to claim 1, wherein: the model of the MCU (6) is an STM32F030C8T6 singlechip.

3. A temperature measuring apparatus for a numerical control machine tool according to claim 1 or 2, wherein: the analog-to-digital converter (8) adopts an AD7793 chip, two matched constant current sources (9) are integrated in the analog-to-digital converter, and the platinum thermal resistor (10) adopts a three-wire PT100 or PT 1000.