Thermocouple transmitter capable of switching measuring range and signal output

Abstract

The utility model relates to a thermocouple transmitter capable of switching measuring range and signal output, which comprises an outer shell formed by buckling an upper shell and a lower shell up and down, and a circuit board is arranged in the upper shell. A first thermocouple signal input terminal, a second thermocouple signal input terminal, a third thermocouple signal input terminal and a fourth thermocouple signal input terminal are arranged at the left end of the circuit board; the right end of the circuit board is provided with a first analog quantity signal output terminal, a second analog quantity signal output terminal, a first power supply input terminal and a second power supply input terminal, the rear end of the circuit board is provided with a communication interface, a first indicating lamp and a second indicating lamp, and the circuit board is also provided with a first dial switch and a second dial switch. According to the utility model, the temperature can be measured by accessing the thermocouple, and the input signal measuring range and the output signal can be changed through the dial switch or the communication interface.

Description

TECHNICAL FIELD

[0001] The utility model relates to thermocouple transmitter technical field especially relates to a thermocouple transmitter of switchable range and signal output. BACKGROUND

[0002] Thermocouple transmitter is a commonly used temperature measuring instrument, and its temperature measuring principle is to convert temperature signals into thermoelectric potential signals through a thermocouple, and the thermoelectric potential is converted into standard electric signals through a transmitting circuit.Thermocouple transmitter has many advantages such as simple structure, convenient manufacturing, wide measuring range, high precision, small inertia and output signal convenient for remote transmission, and is widely used.At present, most thermocouple transmitters have the following defects:

[0003] (1) Most thermocouple transmitters can only be fixed range, and users cannot change the range according to the actual measured temperature.

[0004] (2) Most thermocouple transmitters can only correspond to one kind of thermocouple, and do not support different kinds of thermocouples. Users cannot adjust the corresponding thermocouple model of the transmitter according to the existing thermocouple types on site.

[0005] (3) Most thermocouple transmitters have fixed output signals, and users cannot adjust the output signals of the transmitters according to the receiving equipment in the rear stage. SUMMARY

[0006] The utility model discloses a thermocouple transmitter of switchable range and signal output, which overcomes the above-mentioned problems.

[0007] The utility model discloses a thermocouple transmitter of switchable range and signal output, which overcomes the above-mentioned problems.

[0008] A thermocouple transmitter of switchable range and signal output, which comprises an outer shell composed of an upper shell and a lower shell buckled up and down, a circuit board is arranged in the upper shell, a first thermocouple signal input terminal, a second thermocouple signal input terminal, a third thermocouple signal input terminal and a fourth thermocouple signal input terminal are arranged at the left end of the circuit board, a first analog signal output terminal, a second analog signal output terminal, a first power input terminal and a second power input terminal are arranged at the right end of the circuit board, a communication interface, a first indicator light and a second indicator light are arranged at the rear end of the circuit board, and a first dial switch and a second dial switch are also arranged on the circuit board.

[0009] The circuit board is also provided with a power input circuit, a power isolation conversion circuit, a thermocouple signal sampling circuit, a dial switch circuit, an analog signal output circuit and a single-chip microcomputer circuit, the single-chip microcomputer circuit is connected with the power input circuit, the analog signal output circuit, a communication interface and the dial switch circuit respectively, the power input circuit is connected with the power isolation conversion circuit, and the thermocouple signal is connected to the single-chip microcomputer circuit through the thermocouple signal sampling circuit; the power input circuit reduces the input power and stabilizes the voltage required by the thermocouple transmitter, the analog output circuit converts the thermocouple signal into an analog output signal of a corresponding size according to the size of the thermocouple signal, and finally transmits the signal to the outside through the first analog signal output terminal and the second analog signal output terminal; the thermocouple signal is converted into a voltage signal by the thermocouple signal collection signal on the circuit board and is transmitted to the single-chip microcomputer circuit.

[0010] The thermocouple signal sampling circuit comprises a chip IC6, a chip U8 and TVS tubes TVS2, TVS3 and TVS4, the chip U8 converts the thermocouple signal into a digital signal and transmits the digital signal to the single-chip microcomputer circuit, the TVS tubes TVS2, TVS3 and TVS4 are connected in parallel, the TVS tube TVS2 is connected in parallel with a capacitor C49, the TVS tube TVS3 is connected in parallel with a capacitor C52, and the TVS tube TVS4 is connected in parallel with a capacitor C53.

[0011] The analog voltage AVDD end and the digital voltage DVDD end of the chip U8 are connected with two ends of a resistor R68 respectively, one end of the resistor R68 is connected with the parallel capacitor C54 and C56, and the other end of the resistor R68 is connected with the parallel capacitor C55 and C57; the analog circuit ground AVSS end and the digital circuit ground DVSS end of the chip U8 are connected with two ends of a resistor R74 respectively; the chip U8 is also connected with resistors R70, R71, R72 and R73 respectively.

[0012] Further, the rear end of the lower shell is provided with a flip cover, the flip cover corresponds to the position of the communication interface, the single-chip microcomputer circuit on the circuit board detects the state of the first dial switch and the second dial switch or opens the flip cover to set different ranges of the thermocouple transmitter, analog signal outputs and corresponding thermocouple types through the communication interface.

[0013] Further, the TVS tube TVS2 is also connected with resistors R62, R63 and R64 respectively, the resistor R6 is connected with a capacitor C48 and a signal positive input end, the capacitor C49 is also connected with a capacitor C50 in parallel, and the capacitor C50 is arranged at the signal positive input end and a signal negative input end; the TVS tube TVS3 is also connected with one end of resistors R65 and R66 respectively, a capacitor C51 is arranged between the other ends of the resistors R65 and R66, and the capacitor C51 is connected with the capacitor C52 in parallel.

[0014] Further, the power input circuit comprises a power chip IC4, the power chip IC4 is connected with the parallelly connected pressure resistance RV1, TVS tube TVS1, capacitor C20 and capacitor C21, one end of the pressure resistance RV1 and the TVS tube TVS1 is connected through inductor L3, the other end is connected through inductor L5, one end of the TVS tube TVS1 is connected with diode D7, the diode D7 is connected with capacitor C20 through fuse F1.

[0015] Further, the power isolation conversion circuit comprises chip U6 and transformer T1, the chip U6 is connected with resistor R31 and resistor R31 respectively, the resistor R31 is connected to MOS tube Q4 through capacitor C24, the resistor R32 is connected to MOS tube Q6 through capacitor C27, MOS tube Q4 is connected with MOS tube Q5, MOS tube Q6 is connected with MOS tube Q7, MOS tube Q4, Q5, Q6 and Q7 convert the direct current power into alternating current power, and the isolation conversion is carried out through transformer T1; the transformer T1 is connected with diode D10, D12, D13 and D15 respectively, the diode D10 and D12 are connected with capacitor C25, C26 and voltage stabilizing tube D11 respectively, the diode D13 and D15 are connected with capacitor C29, C30 and voltage stabilizing tube D14 respectively.

[0016] Further, the dial switch circuit comprises dial switch SW1 and dial switch SW2, the dial switch SW1 and the dial switch SW2 are used for detecting input state, the pins 1-8 of the dial switch SW1 are connected with pull-up resistor R44, R47, R49, R51, R53, R55, R57 and R59 respectively, the pins 1-10 of the dial switch SW2 are connected with pull-up resistor R44, R46, R48, R50, R52, R54, R56, R58, R60 and R61 respectively.

[0017] Further, the analog signal output circuit comprises photoelectric coupler U5, chip U4, chip IC2A, chip IC2B, chip IC3A, chip IC3B, optical coupling relay U1 and U3, the photoelectric coupler U5 is connected with chip U4 through resistor R11, the resistor R11 is connected with resistor R8 and voltage stabilizing tube D4 respectively, the chip U4 is connected with series connected resistor R13, R14 and R15, capacitor C12 is connected between resistor R13 and R14, the capacitor C12 is connected with capacitor C14, capacitor C14 is connected to resistor R15, the resistor R15 is connected with chip IC2B, the chip IC2B is connected with capacitor C7 in parallel, the chip IC2B is connected with chip IC3A through resistor R18, the chip IC3A is connected with triode Q3 through resistor R19, the triode Q3 is connected with resistor R12 and resistor R22 respectively, resistor R12 is also connected with chip IC3B and resistor R66, the chip IC3B is connected with triode Q2 through resistor R7, the triode Q2 is connected with triode Q1.

[0018] Further, the voltage input terminal Vin is connected with the chip IC2A, the chip IC2A is connected with the parallel resistance R16 and R20, and is also connected with the resistance R17, and the resistance R16, R17, R20 and the chip IC2A form a voltage output circuit.

[0019] Further, the signal input terminal S21 is connected with the diode D3, the diode D3 is connected with the parallel inductor L1 and L2, the inductor L1 and L2 are connected with the capacitor C10 between one end and the capacitor C9 between the other end, and the capacitor C9 is connected with the diode D5 and the TVS tube D6 in parallel.

[0020] Further, the single-chip microcomputer circuit comprises a chip IC5, a chip U7, a voltage transformer PT1, an indicator lamp LED1 and an interface J1, the chip IC5 calculates a thermocouple signal into a corresponding temperature value and transmits the temperature value to an analog quantity output circuit through a PWM signal, the chip IC5 also receives a code switch state, realizes setting of different temperature ranges and output signals, and the chip U7 stores a temperature table corresponding to the thermocouple; the voltage transformer PT1 is connected with a resistance R40 and is responsible for measuring a temperature on a board; the indicator lamp LED1 is connected with resistances R42 and R43 respectively and is an indicator lamp circuit and is used for indicating a running state and an alarm state of the transmitter; and the interface J1 is a program burning port of the chip IC5.

[0021] Compared with the prior art, the thermocouple transmitter has the beneficial effects that:

[0022] The utility model provides a can switch range and signal output's thermocouple transmitter, including thermocouple signal acquisition circuit, single-chip microcomputer circuit, analog quantity output circuit and power supply circuit, can measure temperature through accessing thermocouple, can change input signal range and output signal through code switch or communication interface simultaneously.

[0023] The utility model supports measuring different temperature ranges, and a user can change an input signal range through a code switch or a communication interface; the utility model supports accessing different types of thermocouples, and a user can adjust a corresponding thermocouple model of the transmitter through a code switch or a communication interface; and a user can adjust an output signal of the transmitter according to a post-stage acquisition device through a code switch or a communication interface. DRAWINGS

[0024] Figure 1 It is a structural schematic diagram of the utility model.

[0025] Figure 2 It is a principle block diagram of the utility model.

[0026] Figure 3 It is a circuit principle diagram of the power input circuit of the utility model.

[0027] Figure 4 The circuit principle diagram of the power isolation conversion circuit of the utility model.

[0028] Figure 5 The circuit principle diagram of the thermocouple signal sampling circuit of the utility model.

[0029] Figure 6 The circuit principle diagram of the dial switch circuit of the utility model.

[0030] Figure 7 The circuit principle diagram of the analog signal output circuit of the utility model.

[0031] Figure 8 The circuit principle diagram of the single-chip microcomputer circuit of the utility model.

[0032] Among them:

[0033] The upper shell 1, the circuit board 2, the communication interface 3, the first indicator lamp 4, the second indicator lamp 5, the first thermocouple signal input terminal 6, the second thermocouple signal input terminal 7, the third thermocouple signal input terminal 8, the fourth thermocouple signal input terminal 9, the flip cover 10, the lower shell 11, the first analog signal output terminal 12, the second analog signal output terminal 13, the first power input terminal 14, the second power input terminal 15, the first dial switch 16, the second dial switch 17. Specific embodiments

[0034] In order to better understand the technical scheme of the utility model, the following will be combined with relevant drawings to make detailed description. It should be understood that the following specific examples are not used to limit the specific implementation of the technical scheme of the utility model, and they are only the implementation of the technical scheme of the utility model. It should be pointed out that the description of the position relationship of each component in this paper, such as A component above B component, is based on the relative position of each component in the drawing, and is not used to limit the actual position relationship of each component. Example 1

[0035] Referring to Figures 1-8 , Figure 1The structure schematic diagram of the utility model is drawn. As shown in the figure, the utility model relates to a thermocouple transmitter capable of switching range and signal output, which comprises an outer shell composed of an upper shell 1 and a lower shell 11 buckled up and down, a circuit board 2 is arranged in the upper shell 1, the left end of the circuit board 2 is provided with a first thermocouple signal input terminal 6, a second thermocouple signal input terminal 7, a third thermocouple signal input terminal 8 and a fourth thermocouple signal input terminal 9, the right end of the circuit board 2 is provided with a first analog signal output terminal 12, a second analog signal output terminal 13, a first power input terminal 14 and a second power input terminal 15, the rear end of the circuit board 2 is provided with a communication interface 3, a first indicator lamp 4 and a second indicator lamp 5, and the circuit board 2 is also provided with a first dial switch 16 and a second dial switch 17.

[0036] The rear end of the lower shell 11 is provided with a flip cover 10, the flip cover 10 corresponds to the position of the communication interface 3, and the different ranges and analog signal outputs of the thermocouple transmitter and the corresponding thermocouple types can be set by opening the flip cover 10 through the communication interface 3.

[0037] Participate Figure 2 , Figure 2 The utility model is the principle block diagram. As shown in the figure, the circuit board 2 is also provided with a power input circuit, a power isolation conversion circuit, a thermocouple signal sampling circuit, a dial switch circuit, an analog signal output circuit and a single-chip microcomputer circuit, the single-chip microcomputer circuit is connected with the power input circuit, the analog signal output circuit, the communication interface and the dial switch circuit respectively, the power input circuit is connected with the analog signal output circuit, the thermocouple signal is connected to the single-chip microcomputer circuit through the thermocouple signal sampling circuit on the circuit board, the input power is reduced and stabilized into the voltage required by the thermocouple transmitter by the power input circuit, the analog output circuit is converted into the analog output signal of the corresponding size according to the thermocouple signal size, and finally the external transmission is carried out through the first analog signal output terminal 12 and the second analog signal output terminal 13.

[0038] The thermocouple signal is converted into the voltage signal by the thermocouple signal acquisition signal on the circuit board 2, and is transmitted to the single-chip microcomputer circuit, the single-chip microcomputer circuit on the circuit board 2 detects the state of the first dial switch 16 and the second dial switch 17, or the different ranges and analog signal outputs of the thermocouple transmitter and the corresponding thermocouple types are set by opening the flip cover 10 through the communication interface 3.

[0039] Participate Figure 3 , Figure 3The utility model discloses a power input circuit's circuit schematic diagram. As shown in the figure, the power input circuit is the power circuit of DC 20~35V input, including power chip IC4, power chip IC4 connects the parallel pressure -sensitive resistance RV1, TVS pipe TVS1, capacitor C20 and capacitor C21, one end of pressure -sensitive resistance RV1, TVS pipe TVS1 is connected through inductance L3, and the other end is connected through inductance L5, one end of TVS pipe TVS1 is connected diode D7, and diode D7 is connected capacitor C20 through fuse F1. Pressure -sensitive resistance RV1, TVS pipe TVS1, inductance L3, inductance L5 constitute the protection of power input EMC, diode D7 plays the role of anti-reverse connection, fuse F1 is current -limiting protection, capacitor C20, C21 play the role of filtering, and power chip IC4 realizes the conversion of output voltage.

[0040] participate Figure 4 , Figure 4 The utility model discloses a power isolation conversion circuit's circuit schematic diagram. As shown in the figure, the power isolation conversion circuit includes chip U6 and transformer T1, chip U6 is connected resistance R31 and resistance R31 respectively, resistance R31 is connected to MOS pipe Q4 through capacitor C24, resistance R32 is connected to MOS pipe Q6 through capacitor C27, MOS pipe Q4 connects MOS pipe Q5, MOS pipe Q6 connects MOS pipe Q7, and MOS pipe Q4, Q5, Q6 and Q7 convert direct current power into alternating current power and isolate and convert through transformer T1;Transformer T1 is connected diode D10, D12, D13 and D15 respectively, diode D10 and D12 are connected capacitor C25, C26 and voltage stabilizing pipe D11 respectively, diode D13 and D15 are connected capacitor C29, C30 and voltage stabilizing pipe D14 respectively. Diode D10 and D12 play the role of rectification, voltage stabilizing pipe D11 plays the role of clamping, capacitor C25 and C26 are filtering, diode D13 and D15 play the role of rectification, voltage stabilizing pipe D14 plays the role of clamping, and capacitor C29 and C30 are filtering.

[0041] participate Figure 5 , Figure 5 The utility model discloses a thermocouple signal sampling circuit's circuit schematic diagram. As shown in the figure, the thermocouple signal sampling circuit includes chip IC6, chip U8 and TVS pipe TVS2, TVS3 and TVS4, and chip U8 converts thermocouple signal into digital signal and transmits to single-chip microcomputer circuit;TVS pipe TVS2, TVS3 and TVS4 are connected in parallel, TVS pipe TVS2 is connected in parallel with capacitor C49, TVS pipe TVS3 is connected in parallel with capacitor C52, and TVS pipe TVS4 is connected in parallel with capacitor C53;

[0042] The TVS tube TVS2 is connected with the positive output end and the negative output end of the transformer for the control circuit power supply respectively, one end of the TVS tube TVS3 and the TVS4 is connected with the positive output end of the transformer, and the other end is connected with the analog ground;

[0043] The TVS tube TVS2 is further connected with resistors R62, R63 and R64 respectively, the resistor R6 is connected with the capacitor C48 and the signal positive input end, the capacitor C49 is further connected with the capacitor C50 in parallel, and the capacitor C50 is arranged at the signal positive input end and the signal negative input end; the TVS tube TVS3 is further connected with one end of the resistors R65 and R66 respectively, and the capacitor C51 is arranged between the other ends of the resistors R65 and R66 and connected, and the capacitor C51 is connected with the capacitor C52 in parallel.

[0044] The pin 1 of the chip IC6 is connected with the resistor R67, and the pin 2 is connected with the digital ground.

[0045] The analog voltage AVDD end and the digital voltage DVDD end of the chip U8 are connected with two ends of the resistor R68 respectively, one end of the resistor R68 is connected with the capacitors C54 and C56 in parallel, and the other end is connected with the capacitors C55 and C57 in parallel; the analog circuit ground AVSS end and the digital circuit ground DVSS end of the chip U8 are connected with two ends of the resistor R74 respectively; the chip U8 is further connected with the resistors R70, R71, R72 and R73 respectively.

[0046] The TVS tubes TVS2, TVS3 and TVS4 are for thermocouple signal clamping effect, the capacitors C49, C52 and C53 are for high frequency absorption effect, the resistors R62 and R64 provide reference level for the thermocouple signal; the resistors R63, R65 and the capacitors C48, C51 are for filtering effect.

[0047] The resistors R70, R71, R72 and R73 are pull-up resistors of the chip U8; the capacitors C54, C55, C56 and C57 are power filter capacitors of the chip U8; the resistors R68 and R74 isolate the digital power supply and the analog power supply of the chip U8, and form single-point connection.

[0048] Participate Figure 6 , Figure 6 It is the circuit principle diagram of the dial switch circuit of the utility model. As shown in the figure, the dial switch circuit comprises dial switches SW1 and SW2, and the dial switches SW1 and SW2 are used for detecting input states, pins 1-8 of the dial switch SW1 are connected with pull-up resistors R44, R47, R49, R51, R53, R55, R57 and R59 respectively, and pins 1-10 of the dial switch SW2 are connected with pull-up resistors R44, R46, R48, R50, R52, R54, R56, R58, R60 and R61 respectively.

[0049] join Figure 7 , Figure 7 This is a schematic diagram of the analog signal output circuit of the present invention. As shown in the figure, the analog signal output circuit includes a photocoupler U5, a chip U4, a chip IC2A, a chip IC2B, a chip IC3A, a chip IC3B, and optocoupler relays U1 and U3. The photocoupler U5 is connected to the chip U4 via a resistor R11. The resistor R11 is respectively connected to the resistor R8 and the voltage regulator D4. The chip U4 is connected to the series resistors R13, R14, and R15. The capacitor C12 is connected between the resistors R13 and R14. The capacitor C12 is connected to the capacitor C1. 4. Capacitor C14 is connected to resistor R15, the resistor R15 is connected to chip IC2B, the chip IC2B is connected to capacitor C7 in parallel, the chip IC2B is connected to chip IC3A via resistor R18, the chip IC3A is connected to transistor Q3 via resistor R19, transistor Q3 is connected to resistor R12 and resistor R22 respectively, resistor R12 is also connected to chip IC3B and resistor R66, the chip IC3B is connected to transistor Q2 via resistor R7, and the transistor Q2 is connected to transistor Q1. U5 isolates and transmits the PWM wave signal. Resistors R8, R11 and Zener diode D4 stabilize the amplitude of the isolated PWM wave signal. Chip U4 performs waveform shaping on the PWM wave signal. The circuit composed of resistors R13, R14, R15, capacitors C12, C14, C7 and chip IC2B outputs a voltage signal of corresponding size according to the duty cycle of the PWM wave. Chips IC3A, IC3B, resistors R19, R22, R66, transistors Q1, Q2 and diode D2 form a current output circuit. Optocoupler relays U1 and U3 switch the current and voltage output circuits.

[0050] The voltage input terminal Vin is connected to the chip IC2A, the chip IC2A is connected to the resistors R16 and R20 connected in parallel, and is also connected to the resistor R17. The resistors R16, R17, R20 and the chip IC2A constitute a voltage output circuit.

[0051] Signal input terminal S21 is connected to diode D3, which is connected to parallel inductors L1 and L2. Capacitor C10 is connected between one end of inductors L1 and L2, and capacitor C9 is connected between the other ends. Capacitor C9 is connected in parallel with diode D5 and TVS diode D6. Diode D3 provides reverse polarity protection, while capacitors C10, C9, inductors L1 and L2 filter out high-frequency interference signals. Diode D5 and TVS diode D6 provide clamping.

[0052] join Figure 8 , Figure 8The circuit principle diagram of the single-chip microcomputer circuit is shown in the figure, and the single-chip microcomputer circuit comprises a chip IC5, a chip U7, a voltage transformer PT1, an indicator lamp LED1 and an interface J1, the chip IC5 calculates a thermocouple signal into a corresponding temperature value, and transmits the temperature value to an analog output circuit through a PWM signal, the chip IC5 also receives a code switch state, realizes setting of different temperature ranges and output signals, the chip U7 stores a temperature table corresponding to the thermocouple, the voltage transformer PT1 is connected with a resistor R40 and is responsible for measuring a temperature on a board, the indicator lamp LED1 is connected with resistors R42 and R43 respectively and is a lamp circuit for indicating a transmitter operating state and an alarm state, and the interface J1 is a program burning port of the chip IC5.

[0053] Working principle:

[0054] The thermocouple transmitter with switchable ranges and signal outputs disclosed by the utility model is centrally installed with a thermocouple signal acquisition circuit, a single-chip microcomputer circuit, an analog output circuit and a power supply circuit in two housings, can measure temperature through two-wire, three-wire and four-wire thermocouples, and can change input signal ranges and output signals through code switches or communication interfaces.

[0055] The installation mode is as follows:

[0056] The communication interface 3, the first indicator lamp 4, the second indicator lamp 5, the first thermocouple signal input terminal 6, the second thermocouple signal input terminal 7, the third thermocouple signal input terminal 8, the fourth thermocouple signal input terminal 9, the first analog signal output terminal 12, the second analog signal output terminal 13, the first power input terminal 14, the second power input terminal 15, the first code switch 16 and the second code switch 17 are welded on the circuit board 2, and the circuit board 2 is installed in the lower housing 11. The flip cover 10 is installed in the lower housing 11, then the upper housing 1 is connected with the lower housing 11 through buckling, and two code switches on the circuit board 2 can be exposed through the opening in the upper housing 1.

[0057] The first power input terminal 14 and the second power input terminal 15 are power input terminals of the thermocouple transmitter, a power circuit on the circuit board 2 steps down the input power and stabilizes the voltage required by the thermocouple transmitter. The first analog signal output terminal 12 and the second analog signal output terminal 13 are output terminals of the analog signal, an analog output circuit on the circuit board 2 converts the thermocouple signal into an analog output signal of a corresponding size according to the size of the thermocouple signal, and finally transmits the analog output signal to the outside through the first analog signal output terminal 12 and the second analog signal output terminal 13. The first thermocouple signal input terminal 6, the second thermocouple signal input terminal 7, the third thermocouple signal input terminal 8 and the fourth thermocouple signal input terminal 9 are input terminals of the thermocouple signal, the thermocouple signal is converted into a voltage signal by a thermocouple signal collection circuit on the circuit board 2, and the voltage signal is transmitted to the single-chip microcomputer circuit. The single-chip microcomputer circuit on the circuit board 2 detects the state of the first DIP switch 16 and the second DIP switch 17, or sets different ranges of the thermocouple transmitter, analog signal outputs and corresponding thermocouple types through the communication interface 3 when the flip cover 10 is opened.

[0058] The above is only a specific application example of the present application, and does not constitute any limitation on the protection scope of the present application. Any technical solution formed by equivalent transformation or equivalent replacement falls within the protection scope of the present application.

Claims

1. A thermocouple transmitter switchable between ranges and signal outputs, characterized by: The application relates to a thermocouple transmitter, which comprises an outer shell composed of an upper shell (1) and a lower shell (11), a circuit board (2) arranged in the upper shell (1), a first thermocouple signal input terminal (6), a second thermocouple signal input terminal (7), a third thermocouple signal input terminal (8) and a fourth thermocouple signal input terminal (9) arranged at the left end of the circuit board (2), a first analog signal output terminal (12), a second analog signal output terminal (13), a first power input terminal (14) and a second power input terminal (15) arranged at the right end of the circuit board (2), a communication interface (3), a first indicator lamp (4) and a second indicator lamp (5) arranged at the rear end of the circuit board (2), and a first dial switch (16) and a second dial switch (17) arranged on the circuit board (2). The circuit board (2) is further provided with a power input circuit, a power isolation conversion circuit, a thermocouple signal sampling circuit, a dial switch circuit, an analog signal output circuit and a single-chip microcomputer circuit, the single-chip microcomputer circuit is connected with the power input circuit, the analog signal output circuit, the communication interface and the dial switch circuit respectively, the power input circuit is connected with the power isolation conversion circuit, the thermocouple signal is connected to the single-chip microcomputer circuit through the thermocouple signal sampling circuit, the power input circuit reduces the input power and stabilizes the voltage required by the thermocouple transmitter, the analog output circuit converts the thermocouple signal into an analog output signal of corresponding size, and finally the first analog signal output terminal (12) and the second analog signal output terminal (13) are used for external transmission. The thermocouple signal is converted into a voltage signal by the thermocouple signal sampling circuit on the circuit board (2) and is transmitted to the single-chip microcomputer circuit, the thermocouple signal sampling circuit comprises a chip IC6, a chip U8 and TVS tubes TVS2, TVS3 and TVS4, the chip U8 converts the thermocouple signal into a digital signal and transmits the digital signal to the single-chip microcomputer circuit, the TVS tubes TVS2, TVS3 and TVS4 are connected in parallel, the TVS tube TVS2 is connected in parallel with a capacitor C49, the TVS tube TVS3 is connected in parallel with a capacitor C52, and the TVS tube TVS4 is connected in parallel with a capacitor C53. An analog voltage AVDD end and a digital voltage DVDD end of the chip U8 are connected with two ends of a resistor R68 respectively, one end of the resistor R68 is connected with a capacitor C54 and a capacitor C56 connected in parallel, and the other end of the resistor R68 is connected with a capacitor C55 and a capacitor C57 connected in parallel, an analog circuit ground AVSS end and a digital circuit ground DVSS end of the chip U8 are connected with two ends of a resistor R74 respectively, and the chip U8 is further connected with resistors R70, R71, R72 and R73 respectively.

2. The thermocouple transmitter of claim 1, wherein: A flip cover (10) is arranged at the rear end of the lower shell (11), the flip cover (10) corresponds to the position of the communication interface (3), the single-chip microcomputer circuit on the circuit board (2) detects the state of the first dial switch (16) and the second dial switch (17) or opens the flip cover (10) to set different ranges of the thermocouple transmitter, analog signal outputs and corresponding thermocouple types through the communication interface (3).

3. The thermocouple transmitter of claim 1, wherein: The TVS tube TVS2 is also connected with resistors R62, R63 and R64 respectively, the resistor R6 connects the capacitor C48 and the signal positive input end, the capacitor C49 is also connected with the capacitor C50 in parallel, and the capacitor C50 is arranged at the signal positive input end and the signal negative input end; the TVS tube TVS3 is also connected with one end of resistors R65 and R66, and the capacitor C51 is arranged between the other ends of the resistors R65 and R66, and the capacitor C51 is connected with the capacitor C52 in parallel.

4. The thermocouple transmitter of claim 1, wherein: The power input circuit comprises a power chip IC4, and the power chip IC4 is connected with the parallelly connected pressure sensitive resistor RV1, TVS tube TVS1, capacitor C20 and capacitor C21, one end of the pressure sensitive resistor RV1 and the TVS tube TVS1 is connected through the inductor L3, and the other end is connected through the inductor L5, one end of the TVS tube TVS1 is connected with the diode D7, and the diode D7 is connected with the capacitor C20 through the fuse F1.

5. The thermocouple transmitter of claim 1, wherein: The power isolation conversion circuit comprises a chip U6 and a transformer T1, the chip U6 is connected with resistors R31 and R31 respectively, the resistor R31 is connected to the MOS tube Q4 through the capacitor C24, the resistor R32 is connected to the MOS tube Q6 through the capacitor C27, the MOS tube Q4 is connected with the MOS tube Q5, the MOS tube Q6 is connected with the MOS tube Q7, the MOS tubes Q4, Q5, Q6 and Q7 inversely convert the direct current power into alternating current power, and the alternating current power is isolated and converted through the transformer T1; the transformer T1 is connected with diodes D10, D12, D13 and D15 respectively, the diodes D10 and D12 are connected with capacitors C25, C26 and voltage stabilizing tube D11 respectively, and the diodes D13 and D15 are connected with capacitors C29, C30 and voltage stabilizing tube D14 respectively.

6. The thermocouple transmitter of claim 1, wherein: The dial switch circuit comprises dial switches SW1 and SW2, and the dial switches SW1 and SW2 are used for detecting input states, pins 1-8 of the dial switch SW1 are connected with pull-up resistors R44, R47, R49, R51, R53, R55, R57 and R59 respectively, and pins 1-10 of the dial switch SW2 are connected with pull-up resistors R44, R46, R48, R50, R52, R54, R56, R58, R60 and R61 respectively.

7. The thermocouple transmitter of claim 1, wherein: The analog signal output circuit comprises an optoelectronic coupler U5, a chip U4, a chip IC2A, a chip IC2B, a chip IC3A, a chip IC3B, optoelectronic coupler relays U1 and U3, the optoelectronic coupler U5 is connected with the chip U4 through a resistor R11, the resistor R11 is connected with a resistor R8 and a stabilizing tube D4 respectively, the chip U4 is connected with resistors R13, R14 and R15 in series, a capacitor C12 is connected between the resistors R13 and R14, the capacitor C12 is connected with a capacitor C14, the capacitor C14 is connected to the resistor R15, the resistor R15 is connected with the chip IC2B, the chip IC2B is connected with the capacitor C7 in parallel, the chip IC2B is connected with the chip IC3A through a resistor R18, the chip IC3A is connected with a transistor Q3 through a resistor R19, the transistor Q3 is connected with a resistor R12 and a resistor R22 respectively, the resistor R12 is also connected with the chip IC3B and a resistor R66, the chip IC3B is connected with a transistor Q2 through a resistor R7, and the transistor Q2 is connected with a transistor Q1.

8. The thermocouple transmitter of claim 1, wherein: A voltage input terminal Vin is connected with a chip IC2A, the chip IC2A is connected with resistors R16 and R20 in parallel and also connected with a resistor R17, and the resistors R16, R17, R20 and the chip IC2A constitute a voltage output circuit.

9. The thermocouple transmitter of claim 1, wherein: A signal input terminal S21 is connected with a diode D3, the diode D3 is connected with inductors L1 and L2 in parallel, a capacitor C10 is connected between one end of the inductors L1 and L2, and a capacitor C9 is connected between the other end of the inductors L1 and L2, the capacitor C9 is connected with a diode D5 and a TVS tube D6 in parallel.

10. The thermocouple transmitter of claim 1, wherein: The single-chip microcomputer circuit comprises a chip IC5, a chip U7, a voltage transformer PT1, an indicating lamp LED1 and an interface J1, the chip IC5 calculates a thermocouple signal into a corresponding temperature value and transmits the temperature value to the analog signal output circuit through a PWM signal, the chip IC5 also receives a state of a code switch to realize setting of different temperature ranges and output signals, the chip U7 stores a temperature table corresponding to the thermocouple; the voltage transformer PT1 is connected with a resistor R40 and is responsible for measuring a temperature on a board; the indicating lamp LED1 is connected with resistors R42 and R43 respectively and is an indicating lamp circuit for indicating a running state and an alarm state of the transmitter; the interface J1 is a program burning port of the chip IC5.

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