CN218068643U - Transmitter for extremely low temperature measurement - Google Patents
Transmitter for extremely low temperature measurement Download PDFInfo
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- CN218068643U CN218068643U CN202222726991.4U CN202222726991U CN218068643U CN 218068643 U CN218068643 U CN 218068643U CN 202222726991 U CN202222726991 U CN 202222726991U CN 218068643 U CN218068643 U CN 218068643U
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Abstract
The utility model relates to a temperature transmitter, in particular to a transmitter for extremely low temperature measurement, which comprises a MCU control unit, an AD conversion circuit, an external device communication circuit, a temperature data conversion circuit and a nixie tube display circuit; the AD conversion circuit is used for receiving an analog voltage signal output by the PT1000 temperature sensor, performing AD conversion on the analog voltage signal after filtering to obtain a digital voltage signal, and outputting a current signal source to the PT1000 temperature sensor to obtain a reference voltage; the MCU control unit is used for receiving the digital voltage signal and the reference voltage sent by the AD conversion circuit and outputting a temperature detection result by combining the digital voltage signal and the reference voltage; the utility model provides a technical scheme can effectively overcome the changer that adopts PT1000 temperature sensor that prior art exists and detect the precision lower under the extremely low temperature condition, can not convert the temperature testing result into the defect of the current signal output of corresponding size.
Description
Technical Field
The utility model relates to a temperature transmitter, concretely relates to be used for extremely low temperature measuring changer.
Background
The PT1000 temperature sensor is a temperature sensor which is manufactured by utilizing a certain functional relation between the resistance value of an internal resistor and the temperature, and is widely used for temperature measurement in a medium temperature range (-200 ℃ -650 ℃) due to high measurement accuracy, large measurement range, good reproducibility and stability and the like. The PT1000 thermal resistor is a widely applied temperature measuring element, and has incomparable advantages including high precision, high stability, strong anti-interference capability and the like of any other temperature sensor in the range of-200 to 170 ℃.
Although the PT1000 thermal resistor can show better stability under the condition of low temperature, the PT1000 thermal resistor has strict temperature and resistance linear relation only above 70K temperature and cannot accurately measure the extremely low temperature between 4K and 70K. Since the resistance of the PT1000 thermal resistor has a non-linear relationship with temperature under very low temperature conditions, a non-linear correction is required. The nonlinear correction is divided into analog circuit correction and microprocessor digital correction, and the analog circuit correction has a plurality of existing circuits, the precision of which is not high and is easily affected by interference factors such as temperature drift. In addition, factors affecting the detection accuracy of the PT1000 temperature sensor under extremely low temperature conditions also include the wiring method and signal quality.
SUMMERY OF THE UTILITY MODEL
Technical problem to be solved
To the above-mentioned shortcoming that prior art exists, the utility model provides a be used for extremely low temperature measuring changer can effectively overcome the changer that adopts PT1000 temperature sensor that prior art exists and detect the precision lower under extremely low temperature condition, can not convert the temperature measurement result into the defect of the current signal output of corresponding size.
(II) technical scheme
In order to achieve the above purpose, the utility model discloses a following technical scheme realizes:
a transmitter for measuring extremely low temperature comprises an MCU control unit, an AD conversion circuit, an external equipment communication circuit, a temperature data conversion circuit and a nixie tube display circuit;
the AD conversion circuit is used for receiving an analog voltage signal output by the PT1000 temperature sensor, filtering the analog voltage signal, performing AD conversion to obtain a digital voltage signal, and outputting a current signal source to the PT1000 temperature sensor to obtain a reference voltage;
the MCU control unit is used for receiving the digital voltage signal and the reference voltage sent by the AD conversion circuit and outputting a temperature detection result by combining the digital voltage signal and the reference voltage;
an external device communication circuit for communicating with an external device;
the temperature data conversion circuit is used for converting the temperature detection result into a current signal with a corresponding magnitude and outputting the current signal;
and the nixie tube display circuit converts the temperature detection result into a display signal and controls the nixie tube to display.
Preferably, the AD conversion circuit includes an AD conversion chip U13, a first filter circuit, a reference voltage generating resistor R25, and a second filter circuit;
the first filter circuit is connected between the PT1000 temperature sensor and the AD conversion chip U13 and is used for filtering analog voltage signals output by the PT1000 temperature sensor;
the AD conversion chip U13 is used for performing AD conversion on the filtered analog voltage signal to obtain a digital voltage signal and outputting a current signal source to the PT1000 temperature sensor;
the reference voltage generating resistor R25 is connected with the PT1000 temperature sensor and used for generating reference voltage under the action of a current signal source;
and a second filter circuit connected between the reference voltage generating resistor R25 and the AD conversion chip U13, for filtering the reference voltage generated by the reference voltage generating resistor R25.
Preferably, the first filter circuit comprises a resistor R17, a resistor R21, a capacitor C36, a capacitor C37 and a capacitor C38, wherein the resistor R17 and the resistor R21 are connected between the PT1000 temperature sensor and a detection signal input pin of the AD conversion chip U13;
one end of the capacitor C36 is grounded, and the other end of the capacitor C36 is connected between the resistor R17 and a detection signal input pin of the AD conversion chip U13;
one end of the capacitor C37 is connected between the resistor R17 and a detection signal input pin of the AD conversion chip U13, and the other end of the capacitor C37 is connected between the resistor R21 and a detection signal input pin of the AD conversion chip U13;
one end of the capacitor C38 is connected to the resistor R21 and the detection signal input pin of the AD conversion chip U13, and the other end is grounded.
Preferably, the second filter circuit comprises a resistor R24, a resistor R26, a capacitor C39, a capacitor C44 and a capacitor C45, wherein the resistor R24 and the resistor R26 are both connected between the reference voltage generating resistor R25 and a reference voltage input pin of the AD conversion chip U13;
one end of the capacitor C39 is grounded, and the other end of the capacitor C39 is connected between the resistor R24 and a reference voltage input pin of the AD conversion chip U13;
one end of the capacitor C44 is connected between the resistor R24 and a reference voltage input pin of the AD conversion chip U13, and the other end of the capacitor C44 is connected between the resistor R26 and the reference voltage input pin of the AD conversion chip U13;
one end of the capacitor C45 is connected to the resistor R26 and a reference voltage input pin of the AD conversion chip U13, and the other end of the capacitor C is grounded.
Preferably, a four-wire wiring is adopted between the PT1000 temperature sensor and the AD conversion chip U13.
Preferably, the external device communication circuit comprises an RS485 isolation transceiver U15 and a protection circuit;
the RS485 isolation transceiver U15 is used for isolating the serial port signal and converting the serial port signal into an RS485 level;
and the protection circuit is used for performing electromagnetic compatibility protection.
Preferably, the protection circuit includes a TVS tube D11, a TVS tube D13, a TVS tube D14, a self-healing fuse R27, a self-healing fuse R28, and a gas discharge tube D12, where the TVS tube D11, the TVS tube D13, and the TVS tube D14 are sequentially connected, the TVS tube D11 is connected with the TVS tube D14, and an output pin of the RS485 isolation transceiver U15 is respectively connected between the TVS tube D11 and the TVS tube D13, and between the TVS tube D13 and the TVS tube D14;
connect self-resuming fuse R27 between TVS pipe D11 and TVS pipe D13, connect self-resuming fuse R28 between TVS pipe D13 and TVS pipe D14, connect gas discharge tube D12 between self-resuming fuse R27, the self-resuming fuse R28.
Preferably, the temperature data conversion circuit converts the temperature detection result into a current signal output of 4-20 mA.
Preferably, the nixie tube display circuit comprises a display chip U7 and a nixie tube U6, wherein the display chip U7 displays and processes the temperature detection result and converts the temperature detection result into a display signal to control the nixie tube U6 to display.
(III) advantageous effects
Compared with the prior art, the utility model provides a be used for extremely low temperature measuring changer has following beneficial effect:
1) The four-wire system wiring and constant current source power supply mode with stronger anti-jamming capability is adopted for high-precision temperature measurement, the four-wire system wiring is adopted between the PT1000 temperature sensor and the AD conversion chip U13, only one constant current source is output by the AD conversion chip U13, the influence of the internal resistance of the lead can be completely eliminated, and the length and the material consistency of the lead are not required to be obtained;
2) The analog voltage signal output by the PT1000 temperature sensor is filtered by the first filter circuit, the reference voltage generated by the reference voltage generating resistor R25 is filtered by the second filter circuit, the signal quality of the analog voltage signal and the reference voltage signal can be effectively improved, and the AD conversion chip U13 carries out AD conversion on the filtered analog voltage signal to obtain a digital voltage signal, so that the MCU control unit can output an accurate temperature detection result by combining the digital voltage signal and the reference voltage;
3) Utilize temperature data converting circuit can convert the temperature measurement result into the current signal output of corresponding size for PLC can be according to current signal size discernment temperature measurement result, and the PLC of being convenient for accomplishes control work better.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below. It is obvious that the drawings in the following description are only some embodiments of the invention, and that for a person skilled in the art, other drawings can be derived from them without inventive effort.
Fig. 1 is an electrical schematic block diagram of the present invention;
fig. 2 is a circuit diagram of the AD conversion circuit of the present invention;
fig. 3 is a circuit diagram of the communication circuit of the external device according to the present invention;
fig. 4 is a circuit diagram of the medium temperature data conversion circuit of the present invention;
fig. 5 is a circuit diagram of a nixie tube display circuit of the present invention;
fig. 6 is a diagram of the utility model.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the drawings in the embodiments of the present invention are combined below to clearly and completely describe the technical solutions in the embodiments of the present invention. It is to be understood that the embodiments described are only some of the embodiments of the present invention, and not all of them. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative efforts belong to the protection scope of the present invention.
A transmitter for measuring extremely low temperature is disclosed, as shown in figure 1, comprising an MCU control unit, an AD conversion circuit, an external device communication circuit, a temperature data conversion circuit and a nixie tube display circuit;
the AD conversion circuit is used for receiving an analog voltage signal output by the PT1000 temperature sensor, performing AD conversion on the analog voltage signal after filtering to obtain a digital voltage signal, and outputting a current signal source to the PT1000 temperature sensor to obtain a reference voltage;
the MCU control unit is used for receiving the digital voltage signal and the reference voltage sent by the AD conversion circuit and outputting a temperature detection result by combining the digital voltage signal and the reference voltage;
an external device communication circuit for communicating with an external device;
the temperature data conversion circuit is used for converting the temperature detection result into a current signal with a corresponding magnitude and outputting the current signal;
and the nixie tube display circuit converts the temperature detection result into a display signal and controls the nixie tube to display.
(1) As shown in fig. 2, the AD conversion circuit includes an AD conversion chip U13, a first filter circuit, a reference voltage generating resistor R25, and a second filter circuit;
the first filter circuit is connected between the PT1000 temperature sensor and the AD conversion chip U13 and is used for filtering an analog voltage signal output by the PT1000 temperature sensor;
the AD conversion chip U13 is used for performing AD conversion on the filtered analog voltage signal to obtain a digital voltage signal and outputting a current signal source (250 muA constant current source) to the PT1000 temperature sensor;
the reference voltage generating resistor R25 is connected with the PT1000 temperature sensor and used for generating reference voltage under the action of a current signal source;
and a second filter circuit connected between the reference voltage generating resistor R25 and the AD conversion chip U13, for filtering the reference voltage generated by the reference voltage generating resistor R25.
1) The first filter circuit comprises a resistor R17, a resistor R21, a capacitor C36, a capacitor C37 and a capacitor C38, wherein the resistor R17 and the resistor R21 are connected between the PT1000 temperature sensor and a detection signal input pin of the AD conversion chip U13;
one end of the capacitor C36 is grounded, and the other end of the capacitor C36 is connected between the resistor R17 and a detection signal input pin of the AD conversion chip U13;
one end of the capacitor C37 is connected between the resistor R17 and the detection signal input pin of the AD conversion chip U13, and the other end of the capacitor C37 is connected between the resistor R21 and the detection signal input pin of the AD conversion chip U13;
one end of the capacitor C38 is connected to the resistor R21 and the detection signal input pin of the AD conversion chip U13, and the other end is grounded.
2) The second filter circuit comprises a resistor R24, a resistor R26, a capacitor C39, a capacitor C44 and a capacitor C45, wherein the resistor R24 and the resistor R26 are connected between a reference voltage generating resistor R25 and a reference voltage input pin of the AD conversion chip U13;
one end of the capacitor C39 is grounded, and the other end of the capacitor C39 is connected between the resistor R24 and a reference voltage input pin of the AD conversion chip U13;
one end of the capacitor C44 is connected between the resistor R24 and the reference voltage input pin of the AD conversion chip U13, and the other end of the capacitor C44 is connected between the resistor R26 and the reference voltage input pin of the AD conversion chip U13;
one end of the capacitor C45 is connected to the resistor R26 and the reference voltage input pin of the AD conversion chip U13, and the other end is grounded.
3) And a four-wire wiring is adopted between the PT1000 temperature sensor and the AD conversion chip U13.
As shown in fig. 2, AIN3 and AIN01 are connected to one end of the PT1000 temperature sensor, AIN11 and REF are connected to the other end of the PT1000 temperature sensor, and a current signal source (250 μ a constant current source) output from the AD conversion chip U13 flows through the PT1000 temperature sensor via AIN3 and then through the reference voltage generating resistor R25, thereby generating a reference voltage between REFP0 and REFN 0.
According to the technical scheme, the high-precision temperature measurement is carried out by adopting a four-wire system wiring and constant current source power supply mode with higher anti-interference capability, the four-wire system wiring is adopted between the PT1000 temperature sensor and the AD conversion chip U13, only the AD conversion chip U13 is required to output one constant current source, the influence of the internal resistance of the lead can be completely eliminated, and the length of the lead and the material are not required to be consistent.
According to the technical scheme, the analog voltage signal output by the PT1000 temperature sensor is filtered by the first filter circuit, the reference voltage generated by the reference voltage generating resistor R25 is filtered by the second filter circuit, the signal quality of the analog voltage signal and the reference voltage signal can be effectively improved, the AD conversion chip U13 performs AD conversion on the filtered analog voltage signal to obtain a digital voltage signal, and the MCU control unit can output an accurate temperature detection result by combining the digital voltage signal and the reference voltage.
(2) As shown in fig. 3, the external device communication circuit includes an RS485 isolation transceiver U15 and a protection circuit;
the RS485 isolation transceiver U15 is used for isolating the serial port signal and converting the serial port signal into an RS485 level;
and the protection circuit is used for performing electromagnetic compatibility protection.
The protection circuit comprises a TVS tube D11, a TVS tube D13, a TVS tube D14, a self-recovery fuse R27, a self-recovery fuse R28 and a gas discharge tube D12, wherein the TVS tube D11, the TVS tube D13 and the TVS tube D14 are sequentially connected, the TVS tube D11 is connected with the TVS tube D14, and an output pin of an RS485 isolation transceiver U15 is respectively connected between the TVS tube D11 and the TVS tube D13 and between the TVS tube D13 and the TVS tube D14;
connect self-resuming fuse R27 between TVS pipe D11 and TVS pipe D13, connect self-resuming fuse R28 between TVS pipe D13 and TVS pipe D14, connect gas discharge tube D12 between self-resuming fuse R27, the self-resuming fuse R28.
As shown in fig. 3, serial port signals RS485_ RX, RX485_ TX, and RS485_ DR are isolated by an RS485 isolation transceiver U15, converted into an RS485 level, and output as an RS485 signal through a protection circuit.
(3) As shown in fig. 4, the temperature data conversion circuit converts the temperature detection result into a current signal of 4-20mA for output, so that the PLC can recognize the temperature detection result according to the magnitude of the current signal, and the PLC can complete the control work better.
(4) As shown in fig. 5, the nixie tube display circuit includes a display chip U7 and a nixie tube U6, and the display chip U7 converts the temperature detection result into a display signal after performing display processing on the temperature detection result, and controls the nixie tube U6 to display the temperature detection result.
The above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; although the present invention has been described in detail with reference to the foregoing embodiments, it should be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; such modifications and substitutions do not depart from the spirit and scope of the present invention in its corresponding aspects.
Claims (9)
1. A transmitter for very low temperature measurement, characterized by: the device comprises an MCU control unit, an AD conversion circuit, an external equipment communication circuit, a temperature data conversion circuit and a nixie tube display circuit;
the AD conversion circuit is used for receiving an analog voltage signal output by the PT1000 temperature sensor, performing AD conversion on the analog voltage signal after filtering to obtain a digital voltage signal, and outputting a current signal source to the PT1000 temperature sensor to obtain a reference voltage;
the MCU control unit is used for receiving the digital voltage signal and the reference voltage sent by the AD conversion circuit and outputting a temperature detection result by combining the digital voltage signal and the reference voltage;
an external device communication circuit for communicating with an external device;
the temperature data conversion circuit converts the temperature detection result into a current signal with a corresponding magnitude and outputs the current signal;
and the nixie tube display circuit converts the temperature detection result into a display signal and controls the nixie tube to display.
2. Transmitter for very low temperature measurements according to claim 1, characterized in that: the AD conversion circuit comprises an AD conversion chip U13, a first filter circuit, a reference voltage generation resistor R25 and a second filter circuit;
the first filter circuit is connected between the PT1000 temperature sensor and the AD conversion chip U13 and is used for filtering an analog voltage signal output by the PT1000 temperature sensor;
the AD conversion chip U13 is used for performing AD conversion on the filtered analog voltage signal to obtain a digital voltage signal and outputting a current signal source to the PT1000 temperature sensor;
the reference voltage generating resistor R25 is connected with the PT1000 temperature sensor and used for generating reference voltage under the action of a current signal source;
and a second filter circuit connected between the reference voltage generating resistor R25 and the AD conversion chip U13, for filtering the reference voltage generated by the reference voltage generating resistor R25.
3. Transmitter for very low temperature measurements according to claim 2, characterized in that: the first filter circuit comprises a resistor R17, a resistor R21, a capacitor C36, a capacitor C37 and a capacitor C38, wherein the resistor R17 and the resistor R21 are connected between a PT1000 temperature sensor and a detection signal input pin of an AD conversion chip U13;
one end of the capacitor C36 is grounded, and the other end of the capacitor C36 is connected between the resistor R17 and a detection signal input pin of the AD conversion chip U13;
one end of the capacitor C37 is connected between the resistor R17 and a detection signal input pin of the AD conversion chip U13, and the other end of the capacitor C37 is connected between the resistor R21 and a detection signal input pin of the AD conversion chip U13;
one end of the capacitor C38 is connected to the resistor R21 and the detection signal input pin of the AD conversion chip U13, and the other end is grounded.
4. Transmitter for very low temperature measurements according to claim 2, characterized in that: the second filter circuit comprises a resistor R24, a resistor R26, a capacitor C39, a capacitor C44 and a capacitor C45, wherein the resistor R24 and the resistor R26 are connected between a reference voltage generating resistor R25 and a reference voltage input pin of an AD conversion chip U13;
one end of the capacitor C39 is grounded, and the other end of the capacitor C39 is connected between the resistor R24 and a reference voltage input pin of the AD conversion chip U13;
one end of the capacitor C44 is connected between the resistor R24 and a reference voltage input pin of the AD conversion chip U13, and the other end of the capacitor C44 is connected between the resistor R26 and the reference voltage input pin of the AD conversion chip U13;
one end of the capacitor C45 is connected to the resistor R26 and a reference voltage input pin of the AD conversion chip U13, and the other end of the capacitor C is grounded.
5. Transmitter for very low temperature measurements according to claim 2, characterized in that: and a four-wire wiring is adopted between the PT1000 temperature sensor and the AD conversion chip U13.
6. Transmitter for very low temperature measurement according to claim 1, characterized in that: the external equipment communication circuit comprises an RS485 isolation transceiver U15 and a protection circuit;
the RS485 isolation transceiver U15 is used for isolating the serial port signal and converting the serial port signal into an RS485 level;
and the protection circuit is used for performing electromagnetic compatibility protection.
7. Transmitter for very low temperature measurements according to claim 6, characterized in that: the protection circuit comprises a TVS tube D11, a TVS tube D13, a TVS tube D14, a self-recovery fuse R27, a self-recovery fuse R28 and a gas discharge tube D12, wherein the TVS tube D11, the TVS tube D13 and the TVS tube D14 are sequentially connected, the TVS tube D11 is connected with the TVS tube D14, and an output pin of the RS485 isolation transceiver U15 is respectively connected between the TVS tube D11 and the TVS tube D13 and between the TVS tube D13 and the TVS tube D14;
connect self-resuming fuse R27 between TVS pipe D11 and TVS pipe D13, connect self-resuming fuse R28 between TVS pipe D13 and TVS pipe D14, connect gas discharge tube D12 between self-resuming fuse R27, the self-resuming fuse R28.
8. Transmitter for very low temperature measurements according to claim 1, characterized in that: and the temperature data conversion circuit converts the temperature detection result into a current signal of 4-20mA for output.
9. Transmitter for very low temperature measurements according to claim 1, characterized in that: the nixie tube display circuit comprises a display chip U7 and a nixie tube U6, the display chip U7 displays and processes a temperature detection result and then converts the temperature detection result into a display signal, and the nixie tube U6 is controlled to display.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202222726991.4U CN218068643U (en) | 2022-10-17 | 2022-10-17 | Transmitter for extremely low temperature measurement |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202222726991.4U CN218068643U (en) | 2022-10-17 | 2022-10-17 | Transmitter for extremely low temperature measurement |
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| Publication Number | Publication Date |
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| CN218068643U true CN218068643U (en) | 2022-12-16 |
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| CN202222726991.4U Active CN218068643U (en) | 2022-10-17 | 2022-10-17 | Transmitter for extremely low temperature measurement |
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