Collection system of card type temperature controller

Abstract

The utility model discloses an acquisition system of a card type temperature controller, which comprises a chip, an RTD sampling circuit, a reference voltage sampling circuit, a switch chip circuit and an RTD interface, the chip is respectively and electrically connected with the RTD sampling circuit, the reference voltage sampling circuit and the switch chip circuit, and the switch chip circuit is electrically connected with the RTD interface. According to the acquisition system of the card type temperature controller, through modular integrated design, multiple protection mechanisms and dynamic characteristic optimization, a temperature acquisition system with higher integration level and stronger anti-interference capability is constructed, a multi-channel control architecture and a standardized interface design are adopted, and improvement of current distribution flexibility and equipment expansibility is realized.

Description

TECHNICAL FIELD

[0001] The utility model relates to temperature control instrument technical field, specifically related to a card formula temperature control instrument's collection system. BACKGROUND

[0002] The collection system is the core basic part of the temperature control instrument, and in the traditional design, the current source and the reference resistance adopt a separate power supply circuit, which leads to the need for additional introduction of current sampling value for RTD resistance value calculation, the increase of formula complexity, the signal crosstalk caused by the parasitic capacitance of the switch during multi-channel switching, the influence on precision, the influence of long reference voltage establishment time on sampling rate, and the lack of effective ESD protection and signal integrity guarantee. UTILITY MODEL CONTENT

[0003] In view of the deficiencies in the background art, the technical problem to be solved by the utility model is to provide a card formula temperature control instrument's collection system with high integration, strong anti-interference ability and fast sampling rate.

[0004] To this end, the utility model is implemented by adopting the following technical scheme:

[0005] A card formula temperature control instrument's collection system, characterized by: including a chip, an RTD sampling circuit, a reference voltage sampling circuit, a switch chip circuit and an RTD interface, the chip is electrically connected with the RTD sampling circuit, the reference voltage sampling circuit and the switch chip circuit respectively, and the switch chip circuit is electrically connected with the RTD interface.

[0006] Further, the RTD sampling circuit comprises an RC filter circuit, an ESD protection circuit and a switch diode, the input end of the RC filter circuit is connected with the RTD interface, the output end is connected with the input end of the ESD protection circuit, the output end of the ESD protection circuit is connected with the anode of the switch diode, and the cathode of the switch diode is connected with the analog input end of the chip.

[0007] Further, the reference voltage sampling circuit comprises a REF RTD current source, a precision resistance and an RC filter network, one end of the REF RTD current source is connected with the precision resistance, the other end of the precision resistance is grounded, and the common end of the REF RTD current source and the precision resistance is connected with the reference voltage input end of the chip through the RC filter network.

[0008] Further, the switch chip circuit comprises an RS2252 type switch chip or an SGM4519XTS16G type switch chip, the switch chip is provided with A / B group control pins for controlling the switching of the current source channel (A IDAC / B IDAC), the reference channel (A REF / B REF) and the signal channel (A AIN / B AIN) respectively.

[0009] Further, the RTD interface supports four-way RTD access, including TC+, TC-, REF+ and REF- four physical interfaces, the TC+ and TC- are used for RTD signal transmission, and the REF+ and REF- are used for reference resistance connection.

[0010] Further, the chip is an HCT6931 chip, the HCT6931 chip is configured with double current sources IDAC0 and IDAC1, the output current gear of the IDAC0 and the IDAC1 is set to 500 mu A, the gain multiple is set to 32 times, and the data sampling rate is set to 25 Hz by default.

[0011] Further, the RC filter network of the reference voltage sampling circuit is composed of a common-mode capacitor C1 and a differential-mode capacitor C2, the C1 value range is 10nF~100nF, and the C2 value range is 1nF~10nF.

[0012] Further, the three-wire PT100 wiring mode of the RTD interface, when the RTD is grounded, the reference resistance is grounded through an independent channel, and an independent reference voltage sampling loop is formed.

[0013] After the above technical scheme, through modular integrated design, multiple protection mechanisms and dynamic characteristic optimization, a temperature collection system with higher integration and stronger anti-interference ability is constructed; through the multi-channel control architecture and the standardized interface design, the current distribution flexibility and the equipment expansibility are improved; with the parameter optimization configuration and the filter network improvement, the measurement accuracy is guaranteed, and low power consumption and high stability are considered; the three-wire PT100 wiring mode further reduces the influence of parasitic potential, so that the overall system can still maintain higher measurement accuracy and lower error rate in complex environments. BRIEF DESCRIPTION OF DRAWINGS

[0014] The utility model has the following drawings:

[0015] Figure 1 It is the structure schematic diagram of the utility model;

[0016] Figure 2 It is the structure schematic diagram of RTD sampling circuit in the utility model;

[0017] Figure 3 It is the structure schematic diagram of reference voltage sampling circuit in the utility model. DETAILED DESCRIPTION

[0018] In order to further illustrate the technical means and effects taken by the utility model to achieve the predetermined utility model purposes, the specific implementation, structure, features and effects according to the utility model are described in detail as follows in combination with the drawings and preferred embodiments.

[0019] With reference to the drawings, the card type temperature control instrument acquisition system provided by the utility model includes a chip, an RTD sampling circuit, a reference voltage sampling circuit, a switch chip circuit and an RTD interface, the chip is electrically connected with the RTD sampling circuit, the reference voltage sampling circuit and the switch chip circuit respectively, the switch chip circuit is electrically connected with the RTD interface, the RTD sampling circuit comprises an RC filter circuit, an ESD protection circuit and a switch diode, the RC filter circuit input end is connected with the RTD interface, and the RC filter circuit output end is connected with the ESD protection circuit input end, the ESD protection circuit output end is connected with the switch diode anode, the switch diode cathode is connected with the chip analog input end, the reference voltage sampling circuit comprises a REF_RTD current source, a precision resistor and an RC filter network, the REF_RTD current source output end is connected with one end of the precision resistor, the other end of the precision resistor is grounded, the common end of the REF_RTD current source and the precision resistor is connected with the chip reference voltage input end through the RC filter network, the switch chip circuit comprises an RS2252 type switch chip or an SGM4519XTS16G type switch chip, the switch chip is provided with A / B group control pins, and is respectively used for controlling the switching of a current source channel (A_IDAC / B_IDAC), a reference channel (A_REF / B_REF) and a signal channel (A_AIN / B_AIN), the RTD interface supports four-way RTD access, comprises four physical interfaces of TC+, TC-, REF+ and REF-, the TC+ and the TC- are used for RTD signal transmission, the REF+ and the REF- are used for reference resistance connection, the chip is an HCT6931 chip, the HCT6931 chip is provided with IDAC0 and IDAC1 double current sources, the output current gear of the IDAC0 and the IDAC1 is set as 500 mu A, the gain multiple is set as 32 times, the data sampling rate is set as 25 Hz by default, the RC filter network of the reference voltage sampling circuit is composed of a common mode capacitor C1 and a differential mode capacitor C2, the C1 value range is 10nF~100nF, the C2 value range is 1nF~10nF, the three-wire PT100 wiring mode of the RTD interface, when the RTD ground, the reference resistance is grounded through an independent channel, and an independent reference voltage sampling loop is formed.

[0020] In the embodiment, by modularly integrating the HCT6931 chip, the RTD sampling circuit, the reference voltage sampling circuit, the switch chip circuit and the RTD interface, physical isolation and electrical isolation of each functional unit are realized, signal crosstalk is avoided, the modular design supports independent upgrading and replacement of each functional module, facilitates subsequent product iteration and maintenance, the integrated structure makes the overall volume smaller and the space utilization higher; the HCT6931 chip communicates with the MCU through the SPI interface, receives current source configuration instructions (such as selecting 500 mu A gear for IDAC0), channel switching instructions (such as selecting the RTD channel CH1) and reference voltage source switching instructions (such as enabling the external reference), the MCU controls the A / B group pins of the switch chip to realize dynamic switching of the RTD signal, the reference resistance and the current source; the RC filter circuit can effectively suppress high-frequency noise above 20 MHz, making the signal-to-noise ratio larger, and the ESD protection circuit and the switching diode double protection make the ESD withstand voltage level higher; the RC filter network is composed of common-mode capacitor C1 and differential-mode capacitor C2, which shortens the reference voltage establishment time, and the precision resistance makes the reference voltage temperature drift smaller, and the independent ground channel design eliminates the ground bounce noise effect; the RS2252 type switch chip can realize 4-way RTD parallel switching, and the channel switching time is shorter; the TC+ / TC- signal line adopts differential shielded wire, which effectively suppresses common-mode interference; the IDAC0 / IDAC1 dual current source (500 mu A gear) makes the RTD self-heating effect lower; the reference resistance independent ground channel makes the compensation error smaller when the RTD is grounded.

[0021] Taking the three-wire PT100 as an example, through the IDAC0 and IDAC1 registers of the HCT6931 chip, the output of the dual current source is set to 500 mu A gear, the current source homologous output mode is enabled, it is ensured that IDAC0 and IDAC1 share the same reference voltage, the PGA (programmable gain amplifier) gain is set to 32 times, the ADC sampling rate is configured to the default 25 Hz, the reference resistance used is 3.9kΩ precision resistance, the external reference mode is selected, the REF+ pin is connected to the middle node of the 3.9kΩ reference resistance, the internal reference voltage source is closed, the external reference input is enabled, and the control instruction is sent to the RS2252 through the SPI bus: the A_IDAC / B_IDAC pin is set to high level, the IOUT0_CH1 and IOUT1_CH1 channels are selected, the A_AIN / B_AIN pin is set to high level, the AIN_P_CH1 and AIN_N_CH1 differential input channels are selected, and the A_REF / B_REF pin is set to high level, the REF_CH1 reference channel is selected.

[0022] Different resistance calculation formulas are adopted for different RTD wiring methods:

[0023] 2-wire RTD: Rsample resistance = AD conversion value / gain / 2^23 * Rreference sample resistance value;

[0024] 3-wire RTD_1: Rsample resistance = AD conversion value / gain / 2^23 * Rreference sample resistance value * 2 (reference resistance grounded);

[0025] 3-wire RTD_2: Rsample resistance = AD conversion value / gain / 2^23 * Rreference sample resistance value (RTD grounded);

[0026] 4-wire RTD: Rsample resistance = AD conversion value / gain / 2^23 * Rreference sample resistance value.

Claims

1. A card-based temperature control instrument acquisition system, characterized by: The chip is respectively connected with the RTD sampling circuit, the reference voltage sampling circuit and the switch chip circuit, and the switch chip circuit is connected with the RTD interface.

2. The card temperature controller collection system according to claim 1, characterized in that: The RTD sampling circuit comprises an RC filter circuit, an ESD protection circuit and a switch diode, the input end of the RC filter circuit is connected with the RTD interface, the output end is connected with the input end of the ESD protection circuit, the output end of the ESD protection circuit is connected with the anode of the switch diode, and the cathode of the switch diode is connected with the analog input end of the chip.

3. The data acquisition system for a card-type temperature controller according to claim 1, characterized in that: The reference voltage sampling circuit comprises a REF RTD current source, a precision resistor and an RC filter network, the output end of the REF RTD current source is connected with one end of the precision resistor, the other end of the precision resistor is grounded, and the common end of the REF RTD current source and the precision resistor is connected with the reference voltage input end of the chip through the RC filter network.

4. The card temperature controller collection system of claim 1, wherein: The switch chip circuit comprises an RS2252 type switch chip or an SGM4519XTS16G type switch chip, the switch chip is provided with A / B group control pins for controlling the switching of current source channels (A IDAC / B IDAC), reference channels (A REF / B REF) and signal channels (A AIN / B AIN).

5. The card temperature controller collection system of claim 1, wherein: The RTD interface supports four-way RTD access, comprises four physical interfaces of TC+, TC-, REF+ and REF-, the TC+ and the TC- are used for RTD signal transmission, and the REF+ and the REF- are used for reference resistance connection. ​ 6. The card temperature controller collection system of claim 1, wherein: The chip is an HCT6931 chip, the HCT6931 chip is provided with double current sources of IDAC0 and IDAC1, the output current gear of the IDAC0 and the IDAC1 is set to 500 mu A, the gain multiple is set to 32 times, and the data sampling rate is set to 25 Hz by default.

7. The card temperature controller collection system of claim 3, wherein: The RC filter network of the reference voltage sampling circuit is composed of a common mode capacitor C1 and a differential mode capacitor C2, the value range of the C1 is 10 nF to 100 nF, and the value range of the C2 is 1 nF to 10 nF.

8. The card temperature controller collection system of claim 5, wherein: The three-wire PT100 wiring mode of the RTD interface, when the RTD is grounded, the reference resistance is grounded through an independent channel, and an independent reference voltage sampling loop is formed.

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