Intrinsic safety type explosion-proof temperature and humidity recorder and temperature and humidity transmitter circuit and device

Abstract

The utility model discloses an intrinsic safety type explosion-proof temperature and humidity recorder and temperature and humidity transmitter circuit and device, and the circuit comprises a 3.7 V rechargeable lithium battery which carries out the voltage stabilization and boost, and provides two types of DC 3V and 5V power supplies needed by the circuit; a data line of the temperature and humidity sensor is connected with an I2C interface of the controller and is connected with the memory to collect and record temperature and humidity data; the flash memory in the controller encrypts and protects application programs and data; the USB interface is connected with a controller data signal line and the communication module to complete RS232 / 485 conversion and terminal data processing and provide a charging power supply; a thermal fusing temperature fuse is arranged in an output loop of the power supply, and a data terminal output loop is provided with increased safety circuits such as a self-recovery fuse and a transient suppression diode. The circuit is low in thermal power consumption and good in explosion-proof effect, meets the regulations and requirements of GB / T 3836.4, and provides a safe intelligent scheme for temperature and humidity measurement in the II-type explosive environment.

Description

Technical Field

[0001] The present application relates to the technical field of industrial temperature and humidity measurement, and in particular to an intrinsically safe explosion-proof temperature and humidity recorder and a temperature and humidity transmitter circuit and device. Background Art

[0002] In the process of modern industrial production management and control, safe production is particularly important. Therefore, when measuring instruments are used in places with certain dangers (such as military industry, chemical industry, bioengineering, mines, etc. containing flammable and explosive gases, liquids, dust, etc.), the measuring and controlling instruments must be guaranteed to have the potential of not igniting and detonating, so as to ensure a safe environment and production. At present:

[0003] 1) The main products on the market are explosion-proof temperature and humidity recorders and temperature and humidity transmitters. However, since explosion-proof instruments generally use external DC12-24V power supplies, there are strict explosion-proof requirements for the sealing ring of the wire entry, the gap sealing of the instrument structure, the number of thread turns of the instrument cover, the thread accuracy, and the window glass. In addition, the explosion-proof shell of the instrument is bulky and does not have a good cost-effectiveness. Users need to regularly inspect and calibrate during use, and cannot operate on site, which brings a lot of trouble and uneconomical process control in the production process. Ordinary temperature and humidity recorders and temperature and humidity transmitters do not have explosion-proof functions and identification.

[0004] 2) There is also an intrinsically safe product circulating in the market, which is mainly composed of temperature and humidity recorders and temperature and humidity transmitters. Generally, digital temperature and humidity sensors or discrete temperature and humidity sensors are used for temperature and humidity measurement. Their common feature is low power consumption (mA level), but there is no application of increased safety components and security measures, which is not enough for intrinsically safe explosion-proof instruments with working current ≧mA level. Although the national standard stipulates: ia level is under normal working conditions, and when there are one or two extreme faults in the circuit, the explosive gas mixture cannot be ignited, and the working current is limited to ≦100mA; ib level is under normal working conditions, and when there is a fault in the circuit, the explosive gas mixture cannot be ignited, and the working current is limited to ≦150mA. However, in actual applications, the market for intrinsically safe explosion-proof products with working currents of ia≦100mA and ib≦150mA is not optimistic, and the safety level is low; there are unpredictable hidden dangers.

[0005] 3) There is also an intrinsically safe circuit circulating on the market, which is mainly composed of temperature and humidity recorders and temperature and humidity transmitters. Their common characteristics are: the output signal is a 4-20mA analog signal, and an external DC24V power supply is required when the recorder (transmitter) is connected to the terminal. This requires the installation of a safety barrier (explosion-proof measure) at the connection point, which reduces safety characteristics and increases costs.

[0006] 4) According to the provisions of the national standard and the International Electrotechnical Commission (IEC) and the requirements of GB / T 3836.1-2021, GB / T3836.4-2021, and GB / T 4208-2008, the intrinsically safe electrical equipment (instruments) with lower working voltage and lower power consumption will have lower surface temperature rise and lower possibility of ignition and explosion under extremely harsh conditions in the application scenario, and will have higher explosion-proof grade, better safety and broader market prospects. The corresponding relationship is as follows:

[0007]

[0008] The highest level, T6, requires that the maximum surface temperature of electrical equipment (instruments) shall not exceed 85°C. At present, under extremely harsh conditions, one or two faults cause serious abnormalities in the V / I of the internal circuit. Due to the lack of safety enhancement measures, the space temperature of the instrument increases. Therefore, it is difficult for intrinsically safe explosion-proof temperature and humidity recorders and temperature and humidity transmitters to meet the T6 standard. There is still a gap in intrinsically safe explosion-proof temperature and humidity recorders and temperature and humidity transmitters with high explosion-proof levels.

[0009] The national standard stipulates that electrical equipment (instruments) installed in hazardous sites with explosive environments must clarify the following issues: whether they have been designed and manufactured in accordance with the requirements of GB / T 3836.1, GB / T 3836.4, and GB / T 4208; and whether they have been certified by explosion-proof testing agencies; the International Electrical Commission (IEC) stipulates that in Zone 0, the most dangerous hazardous location, only Ex ia high-level intrinsically safe explosion-proof technology can be used.

[0010] 5) As we all know, the application of thermal fuse technology in household appliances is very common, but it is rarely used in intrinsically safe explosion-proof instruments. After consulting, it was found that the thermal fuse was connected in series to the circuit that is most susceptible to temperature rise, which is the first application. It also involves the use of TVS transient suppression diodes and self-recovery fuses in series to establish a safety barrier on the circuit of RS232 and RS485 output communication interfaces, which effectively prevents the impact of transient (surge) voltage and current of the external circuit, and effectively controls and protects (prevents) the overall temperature increase of the instrument when the circuit fails suddenly.

[0011] In summary, it is an urgent task for instrument workers to develop an intelligent temperature and humidity measurement circuit and device that meets the requirements of intrinsically safe explosion-proof electrical equipment in terms of circuit and structure. Summary of the invention

[0012] The present application provides an intrinsically safe explosion-proof temperature and humidity recorder and a temperature and humidity transmitter circuit and device, which have the advantage that when working, the maximum surface temperature of the equipment is low, and a higher explosion-proof level can be achieved, meeting the requirements of high-level intrinsically safe explosion-proof instruments and meters.

[0013] On the one hand, the present application provides an intrinsically safe explosion-proof temperature and humidity recorder and a temperature and humidity transmitter circuit, comprising:

[0014] 3.7V rechargeable lithium battery, by stabilizing and boosting the output of the 3.7V rechargeable lithium battery, two working power supplies of DC3V and DC5V are provided, and a thermal fuse and / or a current limiting resistor are provided in the power output circuit;

[0015] MCU controller;

[0016] Temperature and humidity sensor, the data lines SDA and SCL of the temperature and humidity sensor are connected to the I 2 C interface;

[0017] An external memory, which is connected to the MCU controller to collect, record and display temperature and humidity data;

[0018] And LCD display.

[0019] Furthermore, the 3.7V rechargeable lithium battery is connected to a voltage stabilizing circuit and a voltage boosting circuit, the voltage stabilizing circuit outputs DC 3V as output VDD, the voltage boosting circuit outputs DC 5V as output VCC, and a thermal fuse is provided in the power output circuit, and its specification is RH-1A / 70-80°C.

[0020] Furthermore, the temperature and humidity sensor is an ENS210 temperature and humidity sensor, which integrates a relative humidity sensor and a high-precision temperature sensor and is packaged in a QFN4. The output includes a temperature and humidity sensor SDA and SCL data lines through the MCU controller I 2 C interface direct connection.

[0021] Furthermore, it also includes a USB interface, the data signal line in the USB interface is connected to the MCU controller, and the DC 5V+ / - power supply terminal in the USB interface is connected in parallel to two terminals of a 3.7V rechargeable lithium battery to charge the 3.7V rechargeable lithium battery.

[0022] Furthermore, it also includes an RS232 communication module; the RS232 communication module includes a single serial port chip CH340G, a signal conversion chip MAX232 and an RS232 port, the RS232 communication module connects the data signal line in the USB interface and the corresponding connection of the CH340G and MAX232A chips, completes the conversion of RS232 level signals, and is connected to an external terminal through the RS232 port;

[0023] In the RS232 communication module, a thermal fuse is provided in the power supply circuit, and a resettable fuse is connected in series to the signal output end of the signal conversion chip MAX232;

[0024] Furthermore, it also includes an RS485 communication module; the RS485 communication module includes a single serial port chip CH340G, a trigger inverter chip 74HC14H, a signal conversion chip MAX485 and an RS485 port; the RS485 communication module connects the data signal line in the USB interface and the corresponding connections of CH340G, 74HC14H, and MAX485, completes the conversion of RS485 differential signals, and is connected to an external terminal through the RS485 port;

[0025] In the RS485 communication module, a thermal fuse is provided in the power supply circuit, a resettable fuse is connected in series to the signal output A and B terminals of the signal conversion chip MAX485, a TVS transient suppression diode D2 is connected in parallel to the signal output A and B terminals of the signal conversion chip MAX485, and TVS transient suppression diodes D1 and D3 are connected in parallel to the signal output A and B terminals of the signal conversion chip MAX485 and the power supply VCC+ / - terminals, respectively.

[0026] Furthermore, it also includes a memory circuit, wherein the MCU controller is connected to a W25Q serial flash programmable memory to complete the collection, recording, storage and output of more than 48,000 points of resistance / temperature characteristic data;

[0027] The internal flash memory of the MCU controller encrypts and protects the application program and data to prevent access and attack by unauthorized parties.

[0028] Furthermore, it also includes a PVD low voltage detection circuit and / or a hardware low voltage detection circuit, and the PVD low voltage detection circuit is achieved by setting the PVD low voltage detection function end inside the MCU controller through software; the hardware low voltage detection circuit includes resistors R1, R2, R3, R4 and transistor N1, the voltage detection circuit is connected to the output VDD of the power supply, and is connected to the base of the transistor N1 after voltage division by resistors R3 and R4, the collector of the transistor N1 is connected to the output VDD of the power supply through resistor R2, and the voltage across the transistor N1 is connected to the resistor R1 as the output of the voltage detection circuit.

[0029] Furthermore, it also includes an LED alarm circuit and / or a sound alarm circuit, the LED alarm circuit includes an upper limit LED light and a lower limit LED light, the sound alarm circuit includes a buzzer, the buzzer is connected to a transistor N2, the base of the transistor N2 is connected to the MCU controller, and the buzzer is connected in parallel with an inductor L1.

[0030] On the other hand, the present application provides an intrinsically safe explosion-proof temperature and humidity recorder and temperature and humidity transmitter device, including a shell, a circuit board and a sensor probe rod, the circuit board is integrated with the intrinsically safe explosion-proof temperature and humidity recorder and temperature and humidity transmitter circuit as described in any one of the above items, the sensor probe rod includes an aluminum alloy extension tube and a stainless steel powder sintered waterproof protection tube, and the circuit board is insulated and connected to the sensor probe rod.

[0031] In summary, the beneficial effects of this application are:

[0032] 1. The intrinsically safe explosion-proof temperature and humidity recorder and temperature and humidity transmitter circuit provided by the present application is an explosion-proof circuit with lower operating voltage and lower power consumption. The circuit uses a main control MCU controller and additional specific function chips configured as needed, and applies multiple increased safety component protection (protection) technologies, especially the first application of thermal fuses in explosion-proof instruments and meters and the application of TVS transient suppression diodes and self-recovery fuses in series on the loop of RS232 and RS485 output communication interfaces to establish a safety barrier. The above circuit structure is simple, low cost, has good explosion-proof properties and good cost performance; through the above scheme, the maximum surface temperature of the equipment is low (≦85°C), and the highest explosion-proof level (T6) can be achieved;

[0033] 2. The intrinsically safe explosion-proof temperature and humidity recorder and temperature and humidity transmitter circuit provided in this application adopts battery and USB interface DC5V to provide charging guarantee;

[0034] 3. The intrinsically safe explosion-proof temperature and humidity recorder and temperature and humidity transmitter circuit provided by this application are intrinsically safe devices, which do not require a complex, bulky and heavy explosion-proof enclosure. When used in temperature and humidity recorders and temperature and humidity transmitters, they have the characteristics of simple structure, small size, light weight and low cost. According to the data, the cost ratio of establishing an intrinsically safe and explosion-proof switch sensor circuit is about 1:4 (see "Instrument intrinsically safe explosion-proof technology and its application" on the explosion-proof cloud platform);

[0035] 4. The intrinsically safe explosion-proof temperature and humidity recorder and temperature and humidity transmitter circuit provided in this application, when applied to the temperature and humidity recorder and temperature and humidity transmitter, can be maintained, calibrated and repaired on site under power supply; Note: This must be done with the charging power supply and the connection line of the data communication terminal disconnected;

[0036] 5. When the intrinsically safe explosion-proof temperature and humidity recorder and temperature and humidity transmitter circuit provided in this application are applied to the temperature and humidity recorder and temperature and humidity transmitter, damage, leakage, rust and other human factors of the instrument casing will not reduce the safety and reliability of the instrument;

[0037] 6. The intrinsically safe explosion-proof temperature and humidity recorder and temperature and humidity transmitter circuit provided by this application is a weak current technology and therefore will not cause harm to the human body;

[0038] 7. The intrinsically safe explosion-proof temperature and humidity recorder and temperature and humidity transmitter circuit provided in this application have a wide range of applications; the International Electrotechnical Commission (IEC) stipulates that intrinsically safe explosion-proof technology is the only explosion-proof system that can be applied to explosive hazardous locations in Zone 0 (also applicable to Zones 1 and 2). BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a schematic diagram of the overall principle structure of this application scheme;

[0040] Figure 2 It is the common circuit schematic diagram of MCU controller, LCD display, temperature and humidity sensor, etc. in this application scheme;

[0041] Figure 3 It is the schematic diagram of the external memory circuit in the present application scheme;

[0042] Figure 4 This is the schematic diagram of the DC3V power supply circuit in this application scheme;

[0043] Figure 5 This is the schematic diagram of the DC3V and DC5V power supply circuit in this application scheme;

[0044] Figure 6 It is the schematic diagram of the 232 signal conversion circuit in the present application scheme;

[0045] Figure 7 It is the schematic diagram of the 485 signal conversion circuit in the present application scheme;

[0046] Figure 8 It is a schematic diagram of a low voltage detection circuit in the present application scheme;

[0047] Fig. 9 It is the schematic diagram of the LED alarm circuit in this application scheme;

[0048] Fig.10 It is a schematic diagram of the sound alarm circuit in the present application scheme;

[0049] Fig.11 It is a schematic diagram of the outer shape design of the protective shell of the second, third and fourth embodiments of the present application;

[0050] Fig.12 It is a schematic diagram of the appearance of the solutions in Examples 3 and 4 of the present application, wherein the left side is the intrinsically safe explosion-proof intelligent temperature and humidity recorder-232 in Example 3, and the right side is the intrinsically safe explosion-proof intelligent temperature and humidity transmitter-485 in Example 4. DETAILED DESCRIPTION

[0051] The specific implementation of the present application is described in detail below with reference to the accompanying drawings.

[0052] Example 1: Reference Figure 1-8 , an intrinsically safe explosion-proof temperature and humidity recorder and temperature and humidity transmitter circuit, including a power supply, an MCU controller, a temperature and humidity sensor, an LCD display and a memory. The power supply is used to power the temperature and humidity sensor, the MCU controller, the LCD display and the memory. The temperature and humidity sensor is used to detect the temperature and humidity data in the environment and output it to the MCU controller.

[0053] The device also includes a communication module, which is connected to the data signal line of the MCU controller and completes RS232 / 485 conversion, and then connects to the external terminal through the RS232 / 485 port. The power supply supplies power to the communication module. The communication module completes the appropriate high and low level conversion of RS232 and RS485 through the conversion circuit, and connects to the external terminal through the RS232 and RS485 ports with BIT signals that can be read by the computer.

[0054] The communication module is a RS232 communication module or a RS485 communication module.

[0055] The RS232 communication module includes a single serial port chip CH340G, a signal conversion chip MAX232 and an RS232 port. The RS232 communication module connects the data signal line in the USB interface and the corresponding connection of the CH340G and MAX232A chips to complete the conversion of RS232 level signals and connects to an external terminal through the RS232 port;

[0056] In the RS232 communication module, a thermal fuse is provided in the power supply circuit, and a resettable fuse is connected in series to the signal output end of the signal conversion chip MAX232;

[0057] The RS485 communication module includes a single serial port chip CH340G, a trigger inverter chip 74HC14H, a signal conversion chip MAX485 and an RS485 port; the RS485 communication module connects the data signal line in the USB interface and the corresponding connections of CH340G, 74HC14H and MAX485, completes the conversion of RS485 differential signals, and is connected to an external terminal through the RS485 port;

[0058] In the RS485 communication module, a thermal fuse is provided in the power supply circuit, a resettable fuse is connected in series to the signal output A and B terminals of the signal conversion chip MAX485, a TVS transient suppression diode D2 is connected in parallel to the signal output A and B terminals of the signal conversion chip MAX485, and TVS transient suppression diodes D1 and D3 are connected in parallel to the signal output A and B terminals of the signal conversion chip MAX485 and the power supply VCC+ / - terminals, respectively.

[0059] The MCU controller is a 32-bit, high-speed, ultra-low power LQFP64 chip, and the memory is a W25Q serial flash programmable chip. The temperature and humidity sensor is a digital temperature and humidity sensor, specifically ENS210, which integrates a relative humidity sensor and a high-precision temperature sensor and is packaged in a QFN4. It outputs a temperature and humidity sensor SDA and SCL data lines and an MCU controller I 2 The MCU controller is directly connected to the C interface for digital A / D conversion. The MCU controller is connected to an oscillator to provide the operating frequency. The oscillator is an external high-speed 8-12M and low-speed 32.768KHz crystal. The LCD display is connected to the MCU controller SEG digital line and COM address line one by one to realize the detection (display) and recording of temperature and humidity data.

[0060] It also includes a battery, a voltage regulator circuit and a boost circuit. The battery is a 3.7V rechargeable lithium battery. The voltage regulator circuit includes a power regulator regulator 7130. The voltage regulator circuit outputs DC 3V as the output VDD. The output DC3V is used as the working power supply for the MCU controller, the memory and the digital temperature and humidity sensor. The boost circuit includes a power boost regulator 3146. The boost circuit outputs DC 5V as the output VCC. The 3.7V rechargeable lithium battery is boosted by the power boost regulator 3146 to output DC5V to the single serial port chip CH340G, the Schmitt trigger inverter chip 74HC14H and the signal conversion chip MAX232 / MAX485 in the communication module as the working power supply.

[0061] The output circuit of the power supply is equipped with a thermal fuse. The specification of the thermal fuse is RH-1A / 70-80℃, including RH-1A / 70℃, RH-1A / 75℃ and RH-1A / 80℃. When the circuit is applied on the circuit board, the thermal fuse (RH-1A / 70-80℃) is bonded to the copper surface of the circuit board with thermal conductive silicone. As we all know, the application of thermal fuse technology in household appliances is very common, but it is rarely used in intrinsically safe explosion-proof instruments. After consulting, it was found that the thermal fuse is used for the explosion-proof instrument circuit that is most susceptible to temperature rise, which is the first time.

[0062] The output VDD end of the power supply is provided with a current limiting resistor R12, and the resistance value is 100Ω.

[0063] The power supply voltage regulator 7130, current limiting resistor and thermal fuse in the power supply are used to stabilize voltage, limit current and control temperature rise.

[0064] It also includes a USB interface, which is connected to the MCU controller. The DC5V+ / - power line in the USB interface is connected in parallel to two ends of a 3.7V rechargeable lithium battery to provide charging guarantee for the rechargeable lithium battery and power the communication module.

[0065] The USB interface is also used for connection between the MCU controller and the communication module, as follows:

[0066] The DM- of the USB interface is connected to the MCU controller DM- (data negative signal / P44) and the single serial port CH340G chip DM (P6), and the USB interface DP+ is connected to the MCU controller DP+ (data positive signal / P45) and the single serial port CH340G chip DP+ (P5).

[0067] A thermal fuse is provided in the power supply circuit of the communication module, and its specifications and installation method on the circuit board are the same as above.

[0068] In the communication module, a resettable fuse PTC is connected in series at the signal output terminal.

[0069] In the communication module, a TVS transient suppression diode D2 is connected in series between the two signal output terminals, a TVS transient suppression diode D1 is provided between one signal output terminal and the power supply, and a TVS transient suppression diode D3 is provided between the other signal output terminal and the ground. Transient suppression diodes D1 and D3 can absorb the peak voltage in the circuit, thereby protecting the reliability of the entire output terminal.

[0070] The MCU controller RX / IO (PVD / P59) has a direct PVD (low voltage detection) function, which can select a suitable voltage value (for example, 2.8V). At this time, the LCD display shows "LOW BAT or battery default symbol", prompting the user to check the input / output of the working power circuit in time, so as to ensure that the equipment works in a relatively normal state.

[0071] In addition, a hardware circuit may also be used, including a low voltage detection circuit, wherein the low voltage detection circuit includes resistors R1, R2, R3, R4 and a transistor N1. The voltage detection circuit is connected to the output VDD of the power supply, and is connected to the base of the transistor N1 after voltage division by resistors R3 and R4. The collector of the transistor N1 is connected to the output VDD of the power supply through a resistor R2, and the voltage across the transistor N1 is connected to the resistor R1 as the output of the voltage detection circuit.

[0072] It also includes an LED alarm circuit and / or an audio alarm circuit, wherein the LED alarm circuit includes an upper limit LED lamp and a lower limit LED lamp, such as Fig. 9 As shown, the upper limit LED lamp is connected to the power supply at one end and the MCU controller at the other end, which is a positive potential LED lamp. The lower limit LED lamp is connected to the MCU controller at one end and grounded at the other end, which is a negative potential LED lamp. When the MCU controller TX / IO (PB6 / P58) is connected to the LED alarm circuit, according to the set upper and lower limit data (or alarm points), when the upper limit is reached, the positive potential LED lamp lights up, and when the lower limit data is reached, the negative potential LED lamp lights up, thereby completing the light flashing alarm indication function. The sound alarm circuit includes a buzzer, the buzzer is connected to a transistor N2, the base of the transistor N2 is connected to the MCU controller, and the buzzer is connected in parallel with an inductor L1.

[0073] When using sound alarm, the working current consumption will increase, which is not very safe for intrinsically safe explosion-proof instruments. Therefore, the LED alarm circuit is preferred, that is, the light flashing alarm indication function (the LED light-emitting tube should use high-brightness, low-power silicon carbide light-emitting tube).

[0074] It can be understood that the above intrinsically safe explosion-proof temperature and humidity recorder and temperature and humidity transmitter circuit can be applied to intrinsically safe explosion-proof temperature and humidity meters, intrinsically safe explosion-proof temperature and humidity recorders, intrinsically safe explosion-proof temperature and humidity transmitters and other equipment.

[0075] Therefore, in this embodiment, an intrinsically safe explosion-proof temperature and humidity recorder and temperature and humidity transmitter device is also provided, including a shell, a circuit board and a sensor probe rod, the circuit board is integrated with the intrinsically safe explosion-proof temperature and humidity recorder and temperature and humidity transmitter circuit as described in any one of the above items, the sensor probe rod includes an aluminum alloy extension tube and a stainless steel powder sintered waterproof protection tube, and the circuit board is insulated and connected to the sensor probe rod.

[0076] Example 2: Intrinsically safe explosion-proof temperature and humidity recorder

[0077] The recorder is based on the intrinsically safe explosion-proof temperature and humidity recorder and the temperature and humidity transmitter circuit design in the first embodiment, but does not include a communication module, and the power supply only outputs DC3V.

[0078] It is powered by a 3.7V rechargeable lithium battery, and the USB interface DC5V provides charging guarantee. It is stabilized by the power supply regulator 7130, and the output DC3V is used as the working power supply for the MCU controller, memory and digital temperature and humidity sensor, etc. The overall working current (MAX) is small (≦5mA). Therefore, the R12 current limiting resistor and the thermal fuse (RH-1A / 70-80℃) are connected in series to the output (OUT) circuit of the power supply regulator 7130, and bonded to the copper surface with thermal conductive silicone, which can effectively control the maximum surface temperature of the equipment to ≦85℃, so that the product can reach the highest explosion-proof level (T6).

[0079] Example 3: Intrinsically safe explosion-proof intelligent temperature and humidity recorder-232 (Note: the maximum transmission distance is 12-18 meters)

[0080] The recorder is based on the intrinsically safe explosion-proof temperature and humidity recorder and temperature and humidity transmitter circuit design in Example 1, wherein the communication module is used to convert the signal into an RS232 signal, including a single serial port chip CH340G and a signal conversion chip MAX232, and the communication interface is a DB9 / 232 interface for communicating with an external terminal.

[0081] The USB interface DM- is connected to the MCU controller DM- (data negative signal / P44) and the single serial port CH340G chip DM (P6), and the USB interface DP+ is connected to the MCU controller DP+ (data positive signal / P45) and the single serial port CH340G chip DP+ (P5); the single serial port CH340G chip TXD (send / P2) is connected to the signal conversion chip MAX232 / T1IN (P11), and the single serial port CH340G chip RXD (receive / P3) is connected to the signal conversion chip MAX232 / R1OUT (P12), the signal conversion chip MAX232 / T1OUT(P14) is connected in series with T050-110 resettable fuse (i.e., T050 or T110) to the DB9 / 232 interface; the signal conversion chip MAX232 / R1OUT(P14) is connected in series with T050-110 resettable fuse to the DB9 / 232 interface, and the serial port controller is connected to the 232 transceiver with RX and TX signal lines, and the transceiver is connected to the RS232 network bus through level conversion (TTL), and outputs digital signals in the form of high level 1 and low level 0 to connect to the computer, completing data reading, storage, printing and other processing.

[0082] refer to Figure 2-3 , Figure 5-6The circuit is powered by a 3.7V rechargeable lithium battery and the USB interface DC5V provides charging guarantee. It is stabilized by the power regulator 7130 and outputs DC3V for the MCU controller, memory and digital temperature and humidity sensor as the working power supply. The 3.7V rechargeable lithium battery is boosted by the power boost regulator 3146 and the output DC5V is used as the working power supply for the single serial port chip CH340G and the signal conversion chip MAX232. The overall working current (MAX) is within the controllable range (≦50mA). Therefore, a thermal fuse RH-1A / 70-80℃) is set on the output end (OUT) circuit of the power boost regulator 3146, and is bonded to the copper surface of the circuit board with thermal conductive silicone. A self-recovery fuse is connected in series to the output port 232 / TXD of the MAX232 signal conversion chip T1OUT (P14) and the output port 232 / RXD of R1IN (P13), which can effectively control the maximum surface temperature of the equipment to ≦85℃, so that the product can reach the highest explosion-proof level (T6).

[0083] Example 4: Intrinsically safe explosion-proof intelligent temperature and humidity transmitter-485 (Note: the maximum transmission distance is 1200-1800 meters)

[0084] The transmitter is based on the intrinsically safe explosion-proof temperature and humidity recorder and temperature and humidity transmitter circuit design in Example 1, wherein the communication module is used to convert the signal into an RS485 signal, including a single serial port chip CH340G, a Schmitt trigger inverter chip 74HC14H and a signal conversion chip MAX485, and the communication interface is an RS485 interface for communicating with an external terminal.

[0085] The USB interface DM- is connected to the MCU controller DM- (data negative signal / P44) and the single serial port CH340G chip DM- (P6), and the USB interface DP+ is connected to the MCU controller DP+ (data positive signal / P45) and the single serial port CH340G chip DP+ (P5); the single serial port CH340G chip TXD (send / P2) is connected to the Schmitt trigger inverter 74HC14H chip (1A / P1), and the single serial port CH340G chip RXD (receive / P3) is connected to the Schmitt trigger inverter 74HC14H chip (2Y, 3A / P4-5); the Schmitt trigger inverter 74HC14H chip Chip 6Y (P12 / TXD) is connected to the signal conversion chip MAX / 485 / RE-DE (P2-3), and the Schmitt trigger inverter 74HC14H chip 5Y (RXD) is connected to the signal conversion chip MAX / 485 / DI (P4); the serial port controller is connected to the 485 transceiver with RX and TX signal lines (TTL), and the transceiver transmits the differential signal through the cable through the differential line (A and B) and restores the differential signal to TTL signal at the receiving end and connects it to the RS485 network bus, outputs digital signal in the form of high level 1 and low level 0 to connect to the computer, and completes data reading, storage, printing and other processing.

[0086] refer to Figure 2-3 , Figure 5 , Figure 7 The circuit is powered by a 3.7V rechargeable lithium battery and the USB interface DC5V provides charging guarantee. It is stabilized by the power regulator 7130 and outputs DC3V for the MCU controller, W25Q memory and digital temperature and humidity sensor as the working power supply. The 3.7V rechargeable lithium battery is boosted by the power boost regulator 3146 and outputs DC5V for the single serial port chip CH340G, Schmitt trigger inverter chip 74HC14H and signal conversion chip MAX485 as the working power supply. The overall working current (MAX) is within the controllable range (≦50mA). Therefore, a thermal fuse (RH-1A / 70-80℃) is set on the output (OUT) circuit of the power boost regulator 3146, and is bonded to the copper surface of the circuit board with thermal conductive silicone, and a D2 / TVS transient suppression diode is connected in parallel at the output of the MAX485 signal conversion chip A (P6) and the output of the B (P7), and a self-recovery fuse (PTC) is connected in series at the two ends of D2 / TVS to correspond to the two ends of RS485 / A and B. The D1 / D3 / TVS tube can absorb the peak voltage in the circuit, thereby protecting the reliability of the entire machine at the output end. This effectively controls the maximum surface temperature of the device to ≦85℃, so that the product can reach the highest explosion-proof level (T6).

[0087] Design reference for the second, third or fourth embodiment Figure 11-12 ,in, Fig.12 In the figure, the left side is the intrinsically safe explosion-proof intelligent temperature and humidity recorder-232 in Example 3, and the right side is the intrinsically safe explosion-proof intelligent temperature and humidity transmitter-485 in Example 4.

[0088] Embodiment 5: Based on Embodiment 1, 2, 3 or 4, the application program and data are encrypted with the internal flash memory of the MCU controller to prevent access and attack by unauthorized parties. The data is checked and processed on the computer through the APP applet (host computer); the intrinsically safe explosion-proof temperature and humidity recorder in Embodiment 2 is checked and processed on the instrument manually. The MCU controller is connected to the W25Q serial flash programmable memory to complete the collection, recording and storage of temperature and humidity data. Specifically, the W25Q chip CS / chip select signal (P1) is connected to the MCU controller PA4 (P20), the W25Q chip MISO / output data (P2) is connected to the MCU controller PA6 (P22), the W25Q chip CLK / serial clock input signal (P6) is connected to the MCU controller PA5 (P21), and the W25Q chip MOS1 / input data (P5) is connected to the MCU controller PA7 (P23), completing the recording, storage and output of more than 48,000 resistance / temperature characteristic data under APP instructions.

[0089] Program download and debugging, refer to Figure 2 The MCU controller is a 32-bit, high-speed, ultra-low power MCU controller. The edited program can be connected to the SWD interface of the MCU controller through the DEBUG USB serial port interface of the development board. Specifically, the MCU controller SWDIO (PA13 / P46) is connected to USB / D-, and the MCU controller SWDCK (PA14 / P49) is connected to USB / D+ to complete the program download and debugging of the MCU controller.

[0090] Embodiment 6: Based on Embodiment 1, it further includes a reset circuit and a switch circuit. Specifically, Figure 2 , MCU controller NRST (P7) connects S5, R1, and C8. When the instrument freezes, press S5 to complete the instrument reset and wake-up function; MCU controller WKUP (PA0 / P14) connects S1 and R2 to GND in series, MCU controller WKUP (PB2 / P28) connects S2 and R3 to GND in series, MCU controller SEG (PC10 / P51) connects S3 and R4 to GND in series, and MCU controller SEG (PC11 / P52) connects S4 and R5 to GND in series to complete data setting, shifting, and reading.

[0091] Embodiment 7: Based on Embodiment 1, it also has an error correction function. The MCU controller has a large data storage capacity. The + / - system error of temperature and humidity generated during the measurement process can be added or subtracted through software settings, which can greatly increase the accuracy (precision) of the instrument and improve the added value of the product.

[0092] In each embodiment of the present application, the working voltage is DC3V and DC5V, and the maximum working current of the whole machine is within the range of ≦5-50mA. According to the national standard, "the intrinsic safety type ia level is that in normal working state, and when there are one or two extreme faults in the circuit, the explosive gas mixture cannot be ignited, and the working current is limited to ≦100mA; the ib level is that in normal working state, and when there is a fault in the circuit, the explosive gas mixture cannot be ignited, and the working current is limited to ≦150mA". Obviously, the present application meets the requirements of the intrinsic safety type ia on the working current. However, the larger the working current, the faster and greater the temperature rise when one or two extreme faults suddenly occur in the circuit. According to the national standard and the provisions of the International Electrotechnical Commission (IEC), the maximum surface temperature of the dial of T6-level electrical equipment (instruments) shall not exceed 85°C. Therefore, in the communication module of this application, a TVS transient suppression diode and a self-recovery fuse T050-110 are connected in series to the communication interface of RS485 and RS232 outputs to establish a safety barrier, which effectively prevents the transient (surge) voltage and current of the external circuit from rushing out, and effectively controls the maximum surface temperature of the device to ≦85°C, so that the product can reach the highest explosion-proof level (T6).

[0093] Embodiment 8, based on Embodiment 2, 3 or 4, the following process guarantees should be implemented:

[0094] ⑴ The design of the circuit board should comply with the provisions and requirements of the national standard GB / T 3836.1. Therefore, when wiring the circuit board, the spacing width between the lines should be increased to 0.25MM, so as to effectively control the CTI relative tracking index requirements of the PCB board.

[0095] ⑵The product shell should comply with the provisions and requirements of the national standard GB / T 3836.1: When the protective shell is pressed with ABS engineering plastics, its surface insulation resistance should be ≦1GΩ. For this reason, after comparative tests, 757 / ABS+0.25% Mingcheng Tianrun antistatic agent (colorless transparent liquid) is used for pressing. The product is tested by a national professional explosion-proof testing agency, and the surface insulation resistance of its shell is: ≦427.3KΩ, which meets the national standard requirements.

[0096] ⑶ The circuit board should be treated with three-conformal paint for insulation: The circuit board is sprayed with three-conformal paint when it leaves the factory, but after COB bonding and welding of some other parts, the insulation performance of the PCB surface is damaged. Therefore, before the final assembly of the product, an additional process must be added to spray the connection surface of the PCB board and any other welding points with three-conformal paint for more than two times. This effectively protects the circuits and welding points on the surface of the PCB board from oxidation, corrosion and failures caused by damage.

[0097] ⑷ When used in external temperature and humidity sensors, during the assembly process (wire-mounted or armored threaded interface), the sensor probe (aluminum alloy extension tube + stainless steel powder unsintered waterproof protection tube) and the circuit board should be isolated and connected to protect the sensor probe from unexpected external potential influences.

[0098] Compared with the temperature and humidity recorders and temperature and humidity transmitters available on the market, the temperature and humidity recorder-232 and the temperature and humidity transmitter-485 in the embodiments of the present application have better explosion-proof effects, as follows:

[0099]

[0100] The above is only a preferred implementation of the present application. It should be pointed out that a person skilled in the art can make several modifications and improvements without departing from the inventive concept of the present application, and these all fall within the scope of protection of the present application.

Claims

1. Intrinsically safe explosion-proof temperature and humidity recorder and temperature and humidity transmitter circuit, characterized in that: include: 3.7V rechargeable lithium battery, by stabilizing and boosting the output of the 3.7V rechargeable lithium battery, two working power supplies of DC3V and DC5V are provided, and a thermal fuse and / or a current limiting resistor are provided in the power output circuit; MCU controller; Temperature and humidity sensor, the data lines SDA and SCL of the temperature and humidity sensor are connected to the I 2 C interface; An external memory, which is connected to the MCU controller to collect, record and display temperature and humidity data; And LCD display.

2. The intrinsically safe explosion-proof temperature and humidity recorder and temperature and humidity transmitter circuit according to claim 1 is characterized in that: The 3.7V rechargeable lithium battery is connected to a voltage stabilizing circuit and a voltage boosting circuit. The voltage stabilizing circuit outputs DC 3V as output VDD, and the voltage boosting circuit outputs DC 5V as output VCC. A thermal fuse is provided in the power output circuit, and its specification is RH-1A / 70-80°C.

3. The intrinsically safe explosion-proof temperature and humidity recorder and temperature and humidity transmitter circuit according to claim 1, characterized in that: The temperature and humidity sensor is the ENS210 temperature and humidity sensor, which integrates a relative humidity sensor and a high-precision temperature sensor and is packaged in a QFN4 package. It outputs a temperature and humidity sensor SDA and SCL data lines through the MCU controller I 2 C interface direct connection.

4. The intrinsically safe explosion-proof temperature and humidity recorder and temperature and humidity transmitter circuit according to any one of claims 1 to 3, characterized in that: It also includes a USB interface, a data signal line in the USB interface is connected to the MCU controller, and a DC 5V+ / - power supply terminal in the USB interface is connected in parallel to two terminals of a 3.7V rechargeable lithium battery to charge the 3.7V rechargeable lithium battery.

5. The intrinsically safe explosion-proof temperature and humidity recorder and temperature and humidity transmitter circuit according to claim 4, characterized in that: It also includes an RS232 communication module; the RS232 communication module includes a single serial port chip CH340G, a signal conversion chip MAX232 and an RS232 port, the RS232 communication module connects the data signal line in the USB interface and the corresponding connection of the CH340G and MAX232A chips, completes the conversion of RS232 level signals, and is connected to an external terminal through the RS232 port; In the RS232 communication module, a thermal fuse is provided in the power supply circuit, and a resettable fuse is connected in series to the signal output end of the signal conversion chip MAX232.

6. The intrinsically safe explosion-proof temperature and humidity recorder and temperature and humidity transmitter circuit according to claim 4, characterized in that: It also includes an RS485 communication module; the RS485 communication module includes a single serial port chip CH340G, a trigger inverter chip 74HC14H, a signal conversion chip MAX485 and an RS485 port; the RS485 communication module connects the data signal line in the USB interface and the corresponding connections of CH340G, 74HC14H and MAX485 to complete the conversion of RS485 differential signals, and is connected to an external terminal through the RS485 port; In the RS485 communication module, a thermal fuse is provided in the power supply circuit, a resettable fuse is connected in series to the signal output A and B terminals of the signal conversion chip MAX485, a TVS transient suppression diode D2 is connected in parallel to the signal output A and B terminals of the signal conversion chip MAX485, and TVS transient suppression diodes D1 and D3 are connected in parallel to the signal output A and B terminals of the signal conversion chip MAX485 and the power supply VCC+ / - terminals, respectively.

7. The intrinsically safe explosion-proof temperature and humidity recorder and temperature and humidity transmitter circuit according to claim 1, characterized in that: It also includes a memory circuit, wherein the MCU controller is connected to a W25Q serial flash programmable memory to complete the collection, recording, storage and output of more than 48,000 points of resistance / temperature characteristic data; The internal flash memory of the MCU controller encrypts and protects the application program and data to prevent access and attack by unauthorized parties.

8. The intrinsically safe explosion-proof temperature and humidity recorder and temperature and humidity transmitter circuit according to claim 1, characterized in that: It also includes a hardware low voltage detection circuit, which includes resistors R1, R2, R3, R4 and a transistor N1. The voltage detection circuit is connected to the output VDD of the power supply, and is connected to the base of the transistor N1 after voltage division by resistors R3 and R4. The collector of the transistor N1 is connected to the output VDD of the power supply through a resistor R2, and the voltage across the transistor N1 is connected to the resistor R1 as the output of the voltage detection circuit.

9. The intrinsically safe explosion-proof temperature and humidity recorder and temperature and humidity transmitter circuit according to claim 1, characterized in that: It also includes an LED alarm circuit and / or a sound alarm circuit, the LED alarm circuit includes an upper limit LED lamp and a lower limit LED lamp, the sound alarm circuit includes a buzzer, the buzzer is connected to a transistor N2, the base of the transistor N2 is connected to the MCU controller, and the buzzer is connected in parallel with an inductor L1.

10. Intrinsically safe explosion-proof temperature and humidity recorder and temperature and humidity transmitter device, characterized in that: It comprises a shell, a circuit board and a sensor probe rod, the circuit board is integrated with the intrinsically safe explosion-proof temperature and humidity recorder and the temperature and humidity transmitter circuit as described in any one of claims 1 to 9, the sensor probe rod comprises an aluminum alloy extension tube and a stainless steel powder sintered waterproof protection tube, and the circuit board is insulated and connected to the sensor probe rod.

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