A high-precision RTD acquisition device adaptive to two-three-four-wire system

Abstract

The utility model discloses a two three four line system adaptive high accuracy RTD collection device, including control algorithm chip, high accuracy ADC, excitation source, IO control unit, RTD circuit and reference circuit, control algorithm chip is connected with excitation source, and is connected with high accuracy ADC, through the voltage data set that gathers under different circuit, automatically, accurately discerns the RTD actual wiring system of current access, and gathers the RTD circuit resistance value that has determined, real -time upload high accuracy temperature measurement value. Excitation source and IO control unit connection, can control the direction of current input and output, reference circuit is connected with RTD circuit, is used for improving the sampling accuracy based on three four line system method, is used for judging the wiring system of RTD circuit simultaneously. The utility model has the remarkable advantages of realizing the plug and play and high accuracy of RTD measurement, and greatly promotes the easy use, reliability and intelligent level of industrial field.

Description

Technical Field

[0001] This utility model belongs to the field of industrial control, specifically relating to an RTD acquisition device that automatically identifies wiring systems, requires no configuration, and has high precision. Background Technology

[0002] Industrial environments are complex, often containing two-, three-, and four-wire sensors and wiring. Traditional data acquisition devices are inflexible, typically supporting only one wiring method (or requiring manual switching). This leads to frequent configuration errors, reliance on manual settings that are prone to error and difficult to detect; low maintenance efficiency, requiring manual verification of wiring methods when troubleshooting; and a lack of flexibility, unable to adapt to changes in field wiring or mixed deployments.

[0003] In the complex and harsh environments of industrial sites, two-wire, three-wire, and four-wire RTD wiring methods each have significant and insurmountable drawbacks, mainly categorized into four aspects: accuracy, reliability, ease of use, and cost. Traditional two-wire RTD measurement equipment has simple wiring and relatively reliable operation, but it is only suitable for applications with extremely low accuracy requirements and very short leads, and is unsuitable for most industrial measurement and control scenarios. Three-wire systems add a third wire to the two-wire system, and by configuring different current directions, they can eliminate accuracy issues caused by lead resistance. However, in field construction, it is difficult to ensure that the lengths of the three leads, the crimping quality of the terminals, and the degree of oxidation are completely consistent, resulting in unequal lead resistances. Any slight difference will directly translate into temperature error. If one lead breaks or has poor contact, the traditional device may still output a seemingly reasonable temperature value (which is actually incorrect), and the system cannot self-diagnose or alarm, which is an extremely dangerous "silent failure." Three-wire systems offer a compromise between cost and accuracy, but their accuracy is greatly affected by the quality of field construction and line aging, and their reliability is questionable.

[0004] Four-wire systems use four conductors and employ the "Kelvin connection method," eliminating the influence of lead resistance in principle through independent current and voltage sensing lines. This is the most accurate connection method. However, it requires twice the amount of cable and terminals in the field, significantly increasing cabling and installation costs for large-scale applications. Wiring is more complex than two-wire and three-wire systems due to the two additional wires, increasing the workload and the probability of errors. Upgrading a three-wire system to four-wire often requires replacing sensors, cables, and data acquisition equipment, resulting in substantial costs and poor compatibility. While four-wire systems offer the highest accuracy, their high cost and complex compatibility issues limit their widespread adoption in industrial settings. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by providing an RTD acquisition device that can automatically and accurately identify the wiring configuration of the RTD circuit and switch to the optimal measurement mode, thereby achieving intelligent, high-precision, and high-reliability RTD acquisition.

[0006] To achieve the above objectives, this utility model provides a two-, three-, or four-wire adaptive high-precision RTD acquisition device. This high-precision RTD acquisition device includes a control algorithm chip, a high-precision ADC, an excitation source, an I / O control unit, an RTD circuit, and a reference circuit. The control algorithm chip is connected to both the excitation source and the high-precision ADC. The excitation source and the I / O control unit are connected. The reference circuit is connected to the RTD circuit. The high-precision ADC is connected to the RTD circuit. The I / O control module has a built-in multi-channel analog switching circuit. The excitation source outputs a constant current source, which, after being switched by the multi-channel analog switching circuit of the I / O control unit, is connected to the corresponding terminals of the RTD circuit through different loops for current output.

[0007] This invention adjusts the current output of the excitation source by controlling the algorithm chip, dynamically reconstructs the measurement circuit by the IO control module and connects it to a high-precision ADC, analyzes the voltage data sets collected under different circuits, identifies the actual wiring mode of the currently connected RTD, collects the RTD circuit resistance value, and uploads high-precision temperature measurement values ​​in real time.

[0008] Furthermore, the control algorithm chip uses the GD32E508ZET6 chip from the GD series; the excitation source uses a constant current source circuit composed of operational amplifiers and transistors; the high-precision ADC is a 24-bit analog-to-digital converter using the MS5193T chip; the multi-channel analog switching circuit uses a multi-channel analog switch CD4051BM; and the reference circuit uses a loop composed of multiple high-precision resistors. The RTD circuit, or RTD device, is a loop composed of external sensors.

[0009] Furthermore, the aforementioned high-precision ADC is connected to the E and F terminals of the RTD circuit, and the acquired signal voltage is input to the control algorithm chip. When the RTD circuit is a two-wire system, the constant current source output from the excitation source passes through the RTD circuit via the C output of the IO control unit, and then through the B input of the IO control unit. When the RTD circuit is a three-wire system, the constant current source output from the excitation source passes through the B and C outputs of the IO control unit, passes through the RTD circuit, and finally flows to the reference circuit. When the RTD circuit is a four-wire system, the constant current source output from the excitation source passes through the A and C outputs of the IO control unit, passes through the RTD circuit, and finally flows to the reference circuit.

[0010] This invention acquires the signal voltage of the RTD through a high-precision ADC, inputs it to the control algorithm chip for threshold judgment, thereby identifying the wiring pattern of the RTD circuit. Based on the wiring pattern of the RTD circuit, by switching multiple analog switches, a constant current source outputs current through different loops, providing multiple data acquisition methods for the corresponding algorithm.

[0011] This invention has the following advantages over the prior art: This utility model's high-precision RTD acquisition device can automatically, accurately, and reliably identify the wiring system of RTD sensors and switch to the optimal measurement mode without manual intervention. Combined with its internal high-precision ADC, it can effectively improve the sampling accuracy of temperature equipment measured on-site, display changes in on-site temperature in real time, and provide a stable and reliable environment for industry. Attached Figure Description

[0012] Figure 1 This is a block diagram of the overall circuit structure provided by this utility model; Figure 2 Flowcharts of different line type identification processes provided by this utility model; Figure 3 The schematic diagram of the adaptive high-precision device provided by this utility model. Detailed Implementation

[0013] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this utility model. All other embodiments obtained by those skilled in the art based on the described embodiments of this utility model without creative effort are within the scope of protection of this utility model. Unless otherwise defined, the technical or scientific terms used herein should have the ordinary meaning understood by those skilled in the art to which this utility model pertains.

[0014] The terms "first," "second," and similar words used in this utility model patent application specification and claims do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Similarly, unless the context clearly indicates otherwise, the singular forms of "an," "a," or "the," etc., do not indicate a quantity limitation, but rather indicate the presence of at least one. Terms such as "comprising" or "including" indicate that the element or object preceding "comprising" encompasses the features, integrals, steps, operations, elements, and / or components listed following "comprising" or "including," and do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components, and / or collections thereof. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0015] like Figure 1 The present invention is a two-, three-, and four-wire adaptive high-precision RTD acquisition device, which realizes adaptive identification of RTD devices with different wiring systems, and achieves high-precision sampling through a high-precision sampling circuit and a control algorithm chip; it includes a control algorithm chip, a high-precision ADC, an excitation source, an IO control unit, an RTD circuit, and a reference circuit.

[0016] The control algorithm chip is connected to the excitation source to adjust the current output, dynamically reconstruct the measurement circuit, assist in identifying the connection status of two-wire, three-wire and four-wire systems, and is connected to a high-precision ADC. By analyzing the voltage data sets collected under different circuits, it automatically and accurately identifies the actual wiring system of the currently connected RTD circuit, collects the resistance value of the determined RTD circuit, and uploads the high-precision temperature measurement value in real time.

[0017] The excitation source and IO control unit are connected to control the direction of current input and output; the reference circuit is connected to the RTD circuit to improve the sampling accuracy based on the three- or four-wire method, and also to determine the wiring system of the RTD circuit.

[0018] The IO control unit internally incorporates a circuit composed of multiple analog switching switches, which controls current loops. It can dynamically and rapidly input and output the excitation current source according to preset instructions, and output the corresponding current source by switching between different loops and the RTD circuit. In this embodiment, the loops switched in the IO control unit are defined as loop A, loop B, loop C, loop E, and loop F.

[0019] The following description, in conjunction with the embodiments shown in the accompanying drawings, provides a further detailed introduction to the high-precision RTD acquisition device with a two-, three-, or four-wire adaptive system disclosed in this utility model.

[0020] like Figure 3 As shown, the control algorithm chip performs default configuration of the excitation source and high-precision ADC, performs corresponding data interaction, configures the excitation source to output a constant current source, switches the current of loops A and C through the IO control unit, quickly collects a series of voltage data, and after receiving a valid voltage signal, adaptively determines the wiring method of the RTD device.

[0021] like Figure 2 As shown, after the control algorithm chip completes the setting of the excitation source, it outputs a constant current source. The current passes through the IO control unit, loop A outputs the current, passes through the RTD circuit and the reference circuit, and the high-precision ADC will collect the reference voltage Rf at the F terminal and input it to the control algorithm chip for judgment. If the Rf voltage is greater than the threshold set inside the circuit, the RTD circuit is considered to be a four-wire system. If the above conditions are not met, further output and judgment will be performed.

[0022] The control algorithm chip switches multiple analog switches to enable a constant current source to output current to loop C. After passing through the RTD circuit and the reference circuit, the high-precision ADC will sample the reference voltage Rf at terminal F for the second time. If the Rf voltage is greater than its set threshold, the RTD circuit is considered to be three-wire; otherwise, it is considered to be two-wire.

[0023] After determining the wiring configuration of the RTD circuit, the control algorithm chip automatically executes the corresponding precision measurement sequence and calculation algorithm based on the identified wiring configuration. If it is a four-wire system, the Kelvin measurement method is used to directly calculate the RTD resistance value. By controlling the output current of the A circuit, the high-precision ADC measures the voltage value at the E and F terminals. The reference circuit provides the full-scale value. Based on the low temperature drift and high precision characteristics of the external reference, the measured value can be output more accurately, fundamentally eliminating lead wire errors. If it is a three-wire system, the lead resistance compensation algorithm is activated. The output current of the B and C circuits is controlled, and the measurement results are dynamically corrected by measuring the voltage drop of the additional leads through the internal algorithm. In a two-wire system, the sampling loop from C to B uses a proportional measurement algorithm based on a reference resistor to minimize system errors, thereby ensuring the highest measurement accuracy under any connection condition.

[0024] This invention utilizes a control algorithm chip for intelligent identification and multi-loop data acquisition. Within milliseconds, it rapidly constructs and samples various physical measurement loops (two-wire, three-wire, and four-wire) sequentially, providing diverse data for subsequent algorithms and offering adaptive identification capabilities. The core objective is to effectively solve the long-standing problems of complex configuration and error susceptibility in RTD measurement through rational hardware design and intelligent software algorithms. This achieves "plug-and-play" high-precision measurement, significantly improving the system's usability, reliability, and intelligence.

Claims

1. A high-precision RTD acquisition device with two-, three-, and four-wire adaptive architecture, characterized in that, The high-precision RTD acquisition device includes a control algorithm chip, a high-precision ADC, an excitation source, an I / O control unit, an RTD circuit, and a reference circuit. The control algorithm chip is connected to both the excitation source and the high-precision ADC. The excitation source and the I / O control unit are connected. The reference circuit is connected to the RTD circuit. The high-precision ADC is connected to the RTD circuit. The I / O control unit has a built-in multi-channel analog switching circuit. The excitation source outputs a constant current source, which, after being switched by the multi-channel analog switching circuit of the I / O control unit, is connected to the corresponding terminals of the RTD circuit through different loops to output current.

2. The high-precision RTD acquisition device according to claim 1, characterized in that, The control algorithm chip uses the GD32E508ZET6 chip from the GD series; the excitation source uses a constant current source circuit composed of operational amplifiers and transistors; the high-precision ADC uses a 24-bit MS5193T chip; the multi-channel analog switching circuit uses a multi-channel analog switch CD4051BM; and the reference circuit uses a loop composed of multiple high-precision resistors.

3. The high-precision RTD acquisition device according to claim 2, characterized in that, The high-precision ADC is connected to the E and F terminals of the RTD circuit, and the acquired signal voltage is input to the control algorithm chip. When the RTD circuit is two-wire, the constant current source output by the excitation source passes through the RTD circuit via the C channel of the IO control unit, and then through the B channel to the IO control unit. When the RTD circuit is three-wire, the constant current source output by the excitation source passes through the B and C channels of the IO control unit, passes through the RTD circuit, and finally flows to the reference circuit. When the RTD circuit is a four-wire system, the constant current source output by the excitation source is output through the A and C paths of the IO control unit, passes through the RTD circuit, and finally flows to the reference circuit.

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