CN113655075B - Microwave transmission type online detection system for trace moisture in oil and detection method thereof - Google Patents
Microwave transmission type online detection system for trace moisture in oil and detection method thereof Download PDFInfo
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Abstract
A microwave transmission type on-line detection system for trace moisture in oil and a detection method thereof comprise an equipment shell, a detection system circuit board and a sample detection module; the equipment shell comprises an upper shell and a lower shell and is used for fixing the detection system circuit board and the lithium battery; the detection system circuit board comprises a power module, a data processing module, a signal acquisition module, a microwave module and the like, and the lithium battery is connected with the power module of the detection system circuit board; the sample detection module is connected with the detection system circuit board; the invention uses a microwave transmission method to detect trace moisture in oil, has no same application in the field of trace moisture detection, and realizes non-contact online detection; the invention has small volume, can be charged circularly, has simple operation mode and high trace moisture detection precision; the invention can measure the water content below 0.02 percent in the oil, and the detection mode of microwave transmission ensures that the oil product is not polluted, does not generate detection waste liquid, does not corrode detection equipment, and has wide application prospect.
Description
Technical Field
The invention relates to the technical field of trace moisture detection, in particular to a microwave transmission type on-line detection system and a detection method for trace moisture in oil.
Background
At present, the attention on trace moisture in oil is increasingly paid in industrial production, the trace moisture in the oil not only affects the quality of the oil, but also may cause production accidents, for example, quenching oil is a common cooling medium in the quenching process of metal parts, as the service life increases, moisture can be mixed into the quenching oil to cause the quality of the oil to be poor and to lose efficacy, under a high-temperature environment, the moisture contained in the quenching oil can also bring fire hazard, because the moisture in the quenching oil can boil and expand at a high temperature, the quenching oil overflows from a quenching bath, and if the overflowing quenching oil meets a high-temperature object, a fire hazard can be caused. Generally, the water content in quenching oil needs to be controlled below 0.03%, attention needs to be paid when the water content in the quenching oil is more than 0.02%, at present, equipment capable of detecting trace water in the oil is divided into an off-line type and an on-line type, off-line type measurement needs detection personnel to perform a series of complex operations, a lot of chemical reagents are used, and the biggest problem of off-line type measurement is that the waiting time is long, the measurement result is not real-time, and real-time monitoring of an industrial field cannot be realized; the online measuring equipment has the advantages of simple operation and real-time result display. Patent document No. 202011168084.1 discloses a remote crude oil water content measuring device and a measuring method thereof based on a microwave transmission method. According to the method, the detection of the water content in the crude oil is realized by a method for detecting the microwave loss value, the detection result can be uploaded to a cloud end, and online and non-contact detection is realized, but the method also has the defects that the detection precision is not high enough, the water content below 0.1% in the oil cannot be detected, the condition that the water content exceeds the standard cannot be warned, and the equipment volume is not small enough. The existing online trace moisture detection equipment is in contact detection, and some equipment also needs additional chemical reagents, so that oil products are polluted, equipment sensors are corroded, and waste liquid generated by detection needs special treatment. Therefore, an online detection device for trace moisture in oil, which can realize non-contact measurement, is needed, and can ensure the real-time performance of the detection result, the quality of the oil product and the service life of the device.
Disclosure of Invention
In order to overcome the defects in the prior art, the invention aims to provide a microwave transmission type high-precision online detection system and a detection method thereof for trace moisture in oil, which can realize non-contact measurement, ensure the real-time performance of a detection result, ensure the quality of an oil product and prolong the service life of equipment.
In order to achieve the purpose, the technical scheme provided by the invention is as follows:
the utility model provides a microwave transmission type high accuracy on-line measuring system of trace moisture in oil, include that upper casing 1 and lower casing 2 lock joint the equipment shell 20 that forms together, equipment shell 20 internally mounted has lithium cell 40 and detecting system circuit board 30 to and with detecting system circuit board 30 signal connection and lie in the outside sample detection module 90 of equipment shell 20, wherein detecting system circuit board 30 passes through the locating hole and installs inside upper casing 1, lithium cell 40 installs inside lower casing 2, lithium cell 40 provides 12V's direct current electric energy for detecting system circuit board 30.
The detection system circuit board 30 comprises a power supply module 50, a data processing module 60, a signal acquisition module 70 and a microwave module 80; the input end of the power supply module 50 is connected with the lithium battery 40, and the output end of the power supply module 50 is connected with the data processing module 60, the signal acquisition module 70 and the microwave module 80 for power supply; the data processing module 60 is connected with the signal acquisition module 70 and receives the data sent by the signal acquisition module 70 to calculate the trace moisture, and meanwhile, the data processing module 60 displays the trace moisture calculation result in real time; the signal acquisition module 70 is connected with the microwave module 80 to receive the voltage signal of the microwave module 80 and output a digital signal to the data processing module 60 through signal conversion; the microwave module 80 is connected to the sample detection module 90, and detects the attenuation of the microwave signal power by transmitting and receiving the microwave signal, and converts the power values of the transmitting end and the receiving end into corresponding voltage values respectively, and outputs the voltage values to the signal acquisition module 70.
The sample detection module 90 comprises a transmitting terminal antenna 901, a receiving terminal antenna 903 and a sample test container 902, wherein the transmitting terminal antenna 901 receives microwave signals generated by the microwave module 80 and emits the microwave signals to the air, the receiving terminal antenna 903 receives the microwave signals emitted by the transmitting terminal antenna 901 and transmits the microwave signals to the microwave module 80, the microwave signals penetrate through a sample to be tested in the sample test container 902 to be subjected to power attenuation, the sample test container 902 is used for placing an oil sample to be tested and fixing the volume of the sample to be tested, and the transmitting terminal antenna 901 and the receiving terminal antenna 903 are respectively installed at two ends of the sample test container 902.
The data processing module 60 comprises a singlechip minimum system 601, a display screen module 602, a debugging serial port 603 and a function key 604;
the single chip microcomputer minimum system 601 is used for receiving 16-bit data sent by the signal acquisition module, wherein the 16-bit data is a group of digital signals converted from analog voltage signals acquired by the microwave module by the signal acquisition module; meanwhile, the singlechip minimum system calculates the 16-bit data through an internal trace moisture calculation program to obtain trace moisture information of the tested sample and sends the trace moisture information to a display screen module; the single chip microcomputer minimum system also selects program functions and debugs and programs through the function keys and the debugging serial port;
the display screen module 602 is used for dynamically displaying the value of the trace moisture of the tested sample, the residual electric quantity information of the lithium battery and the warning information;
the debugging serial port 603 is used for connecting the detection system circuit board with an external upper computer, performing program debugging and program programming and sending data of the detection system circuit board to the upper computer;
the function key 604 is used for selecting a function of a program in the minimum system 601 of the single chip microcomputer, and realizing a function of displaying a numerical value, recording a curve, warning and detecting the excessive moisture and debugging the program.
The signal acquisition module 70 includes a first operational amplifier 701, a second operational amplifier 702, a subtractor 703 and an ADC chip 704;
the first operational amplifier 701 is used for performing adjustable multiple amplification on the output voltage of the first logarithmic detector 805 to enable the output voltage of the first operational amplifier 701 to be just 3.3V, and the output voltage of the first operational amplifier 701 is used as a reference value in the trace moisture calculation process, namely an unattenuated microwave power value;
the second operational amplifier 702 is configured to perform adjustable multiple amplification on the output voltage of the second logarithmic detector 809, so that the output voltage of the second operational amplifier 702 is 3.3V when the sample to be tested is not loaded in the sample testing container, that is, the difference between the output voltages of the first operational amplifier 701 and the second operational amplifier 702 is substantially 0;
a subtractor 703 for subtracting the output voltages of the first operational amplifier 701 and the second operational amplifier 702, amplifying the subtracted voltage by 100 times and outputting the amplified voltage to the ADC chip 704;
and the ADC chip 704 is configured to acquire a voltage signal output by the subtractor 703, convert the voltage signal into a corresponding 16-bit digital signal, and send data to the minimum system of the single chip microcomputer through an SPI protocol.
The microwave module 80 comprises a voltage-controlled oscillator 801, a variable gain amplifier 802, a first band-pass filter 803, a first directional coupler 804, a first logarithmic detector 805, a strip line isolator 806, a second band-pass filter 807, a second directional coupler 808, a second logarithmic detector 809, a negative voltage power supply 810 and a precision adjustable resistor 811; and the voltage-controlled oscillator 801 is used for generating a 10GHz microwave signal.
The variable gain amplifier 802 is configured to amplify or attenuate the microwave signal output by the voltage controlled oscillator 801 by a controllable gain to achieve the purpose of controlling the transmission power. The gain control voltage of the variable gain amplifier 802 is provided by a negative voltage power supply and is precisely adjusted through a precisely adjustable resistor to realize the change between-3.3V and-1V, and the gain value of the variable gain amplifier is changed between-2 dB and 16 dB.
The first band pass filter 803 is used for band pass filtering the transmitting end microwave signal to reduce harmonic noise of the microwave signal.
And the first directional coupler 804 is used for coupling the microwave signal power on the transmission line of the transmitting end, and the microwave signal power obtained by coupling reflects the value of the microwave signal power of the transmitting end.
And a first logarithmic detector 805 for detecting the power of the microwave signal output by the first directional coupler 804 and outputting a corresponding direct current voltage to reflect the power of the microwave signal received by the first directional coupler.
The strip line isolator 806 is used to isolate the reflected signal at the transmitting end, so that the reflected signal cannot return to the first directional coupler 804.
A second band-pass filter 807 for band-pass filtering the receiving-end microwave signal.
And a second directional coupler 808 for coupling the microwave signal power on the transmission line of the receiving end.
And a second logarithmic detector 809 for detecting the power of the microwave signal output by the second directional coupler 807 and outputting a corresponding dc voltage to reflect the power of the microwave signal received by the second directional coupler.
The negative voltage power supply 810 is used to generate a-3.3V dc voltage to provide a negative voltage to the gain control terminal and the gate control terminal of the variable gain amplifier 802.
The precision adjustable resistor 811 is used to form a series voltage divider circuit to make the voltage output to the gain control terminal of the variable gain amplifier 802 vary from-3.3V to-1V.
The upper shell 1 and the lower shell 2 of the equipment shell are of asymmetric structures, the matching surface of the upper shell 1 and the lower shell 2 is buckled in an internal-external staggered mode, and the upper shell 1 and the lower shell 2 are fixed through screws.
The upper shell 1 is used for fixing a detection system circuit board and reserving an opening for a structural member of the detection system circuit board, the opening of the upper shell 1 comprises a display screen module opening 3, a function key opening 4, a microwave module transmitting end opening 9 and a microwave module receiving end opening 10, and the upper shell also comprises a detection system circuit board fixing hole 5, an anti-reverse installation structure 6 and an upper shell and lower shell mounting hole 7;
The first band-pass filter 803 and the second band-pass filter 807 are microstrip line devices, the 3dB bandwidth of the microstrip line devices is 9GHz-11 GHz, the center frequency of the microstrip line devices is 10GHz, the insertion loss at 10GHz is 0.7dB, the first band-pass filter 803 and the second band-pass filter 807 adopt a mode of combining a step impedance line and a parallel coupling line, and the structure is as follows: the input port 1001, the first impedance-step resonator 1002, the interdigital parallel coupling line 1003, the second impedance-step resonator 1004, and the output port 1005 are connected in this order, the input port of the first band-pass filter 803 is connected to the variable gain amplifier 802, and the output port is connected to the first directional coupler 804. The input port of the second band-pass filter 807 is connected to the receiving-end antenna 903, and the output port is connected to the second directional coupler 808.
The signal acquisition module 70 utilizes the output voltage of the first logarithmic detector 805 and the output voltage of the second logarithmic detector 809 in the microwave module as the signal processing and acquisition object, the output voltage of the first logarithmic detector 805 and the output voltage of the second logarithmic detector 809 are respectively amplified by the first operational amplifier 701 and the second operational amplifier 702, when no sample to be tested is added, the output voltage of the first operational amplifier 701 and the output voltage of the second operational amplifier 702 are equal, when a sample to be tested containing water is added, the output voltage of the second logarithmic detector 809 is attenuated, so that the output voltage of the second operational amplifier 702 is also reduced, at the moment, the output voltage of the first operational amplifier 701 and the output voltage of the second operational amplifier 702 are also reducedThe output voltage of 701 and the output voltage of the second operational amplifier 702 are different, and the difference is made by a subtracter 703, and the difference is amplified by 100 times and then input to an ADC chip 704 for voltage acquisition, wherein the relation between the output voltage of the subtracter 703 and the input voltage is V OUT ＝100*(V IN+ -V IN- ) In which V is OUT The voltage, V, input to the ADC chip 704 for the subtractor 703 IN+ Is the output voltage, V, of the first operational amplifier 701 IN- The ADC acquisition value of the ADC chip 704 for voltage acquisition for the output voltage of the second operational amplifier 702 has a range of 0-65535, if (V) IN+ -V IN- ) If Δ V is recorded, the relationship between the ADC acquisition value data and the voltage difference Δ V is
The invention also provides a detection method of the microwave transmission type high-precision online detection system for trace moisture in oil, which comprises the following steps:
the method comprises the steps of adding a tested oil product into a sample testing container 902, enabling the oil level height to reach a scale mark in the sample testing container 902, then starting a power switch of a detection system, generating a microwave signal with the frequency of 10GHz after the system is powered on, transmitting and receiving the microwave signal through a transmitting end antenna 901 and a receiving end antenna 903 to enable the microwave signal to be attenuated when the microwave signal transmits through the tested oil product, respectively detecting a transmitter and a receiver of a microwave module 80 through a first logarithmic detector 805 and a second logarithmic detector 809 to obtain a microwave signal power value transmitted by the transmitting end antenna 901 and a microwave signal power value received by the receiving end antenna 903 and output corresponding direct current voltage signals, amplifying the voltage signals corresponding to the microwave signal power values of the transmitter and the receiver through a first operational amplifier 701 and a second operational amplifier 702 to achieve the effect that the microwave signal is not attenuated when the microwave signal is not attenuated, gradually reducing the output voltage of the second operational amplifier 702, namely the microwave signal power voltage of the receiver microwave signal power when the microwave signal is attenuated, substituting the two voltage signals into a subtractor 703 circuit to achieve the effect that the micro-power attenuation data is obtained by further amplifying the micro-micro attenuation data, and finally displaying the micro-level of the micro-based on the micro-detection and the micro-quantity acquired by an ADC chip 602 to obtain the micro-based on the micro-scale detection.
The innovation points of the invention are as follows:
(1) The method for detecting trace moisture in oil by using microwave transmission is not applied in the field of trace moisture detection, and non-contact on-line detection is realized.
(2) By adopting an integrated circuit design method, the detection system has a small volume, the detection precision is hardly influenced, the operation steps are simple, and the detection result is displayed in real time.
(3) The difference value of detection voltage signals of the transmitter and the receiver is amplified by 100 times by adopting the subtracter circuit, the numerical value of the difference value of the two paths of voltages is further amplified under the condition that the voltage acquisition precision is not changed, the detection sensitivity of the system is improved by 100 times, and the detection sensitivity is improved on the premise that the cost is hardly increased.
(4) The voltage signal is subjected to proportion and subtraction operation by using a hardware circuit, the precision and reliability are higher compared with the signal processing by using a software program, the digital signal output by the ADC chip directly reflects the power attenuation value of the microwave signal, the anti-interference performance is higher than that of the output analog signal, the occupation of an I/O port of the single chip microcomputer is reduced, and meanwhile, the detection error caused by the asynchronous acquisition of multi-path voltage by the single chip microcomputer is avoided.
Drawings
FIG. 1 is an overall system block diagram of the present invention.
FIG. 2 is a system block diagram of the main functional circuits and modules of the present invention.
Fig. 3 is an isometric view of a housing of the apparatus of the present invention.
FIG. 4 is a front view of a sample detection module of the present invention.
Fig. 5 is a front view of the structure of the first band pass filter and the second band pass filter of the present invention.
Fig. 6 is a circuit schematic of the voltage controlled oscillator of the present invention.
Fig. 7 is a circuit schematic of the variable gain amplifier of the present invention.
FIG. 8 is a schematic circuit diagram of a first logarithmic detector and a second logarithmic detector of the present invention.
Fig. 9 is a circuit schematic of a first operational amplifier of the present invention.
Fig. 10 is a circuit schematic of a second operational amplifier of the present invention.
Fig. 11 is a circuit schematic of the subtractor of the present invention.
Fig. 12 is a circuit schematic of an ADC chip of the present invention.
Fig. 13 is a circuit schematic diagram of the minimum system of the single chip microcomputer.
Fig. 14 is a schematic circuit diagram of a display panel module of the present invention.
FIG. 15 is a graph comparing the results of actual tests of the present invention with calibration functions.
Fig. 16 shows system information and trace moisture information displayed on the display panel module according to the present invention.
Wherein: 1-an upper housing; 2-a lower housing; 3-display screen module opening; 4-function key opening; 5-detecting a system circuit board fixing hole; 6-anti-reverse installation structure; 7-upper and lower housing mounting holes; 8-power switch opening; 9-microwave module emission end opening; 10-microwave module receiving end opening; 11-lithium battery charging opening; 901-a transmitting end antenna; 902-a specimen test container; 903-receiving end antenna; 1001-input port; 1002-a first step impedance resonator; 1003-interdigital parallel coupling lines; 1004-a second step-impedance resonator; 1005-output port.
Detailed Description
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following description will be made with reference to the accompanying drawings. It is obvious that the drawings in the following description are only some examples of the invention, and that for a person skilled in the art, other drawings and embodiments can be derived from them without inventive effort.
For the sake of simplicity, the drawings only show schematically the parts relevant to the invention, and they do not represent the actual structure as a product. Moreover, in the interest of brevity and understanding, only one of the components having the same structure or function is illustrated schematically or designated in some of the figures. In this document, "one" means not only "only one" but also a case of "more than one".
In the context of the present disclosure, when a layer/element is referred to as being "on" another layer/element, it can be directly on the other layer/element or intervening layers/elements may be present. In addition, if a layer/element is "on" another layer/element in one orientation, then that layer/element may be "under" the other layer/element when the orientation is reversed.
It should be noted that the terms "first," "second," and the like in the description and claims of the present invention and in the drawings described above are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the invention described herein are capable of operation in sequences other than those illustrated or described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.
As shown in figure 1, a microwave transmission type high-precision online detection system for trace moisture in oil comprises an upper shell 1 and a lower shell 2 which are buckled together to form an equipment shell 20, wherein a lithium battery 40 and a detection system circuit board 30 are arranged in the equipment shell 20, the detection system circuit board 30 is in signal connection with the detection system circuit board 30 and is located outside the equipment shell 20, the detection system circuit board 30 is arranged in the upper shell 1 through a positioning hole, the lithium battery 40 is arranged in the lower shell 2, the lithium battery 40 provides 12V direct current electric energy for the detection system circuit board 30, and the normal work of the detection system circuit board is ensured, and the lithium battery can be charged circularly. As shown in fig. 2, 3 and 4, the detection system circuit board 30 is fixed to the detection system circuit board fixing holes 5 of the upper case 1 by screws through fixing holes at four corners thereof, the lithium battery 40 is fixed to the inside of the lower case 2, and the upper case 1 and the lower case 2 are fixed by screws through the upper and lower case mounting holes 7.
The detection system circuit board 30 is used for generating a microwave signal with a frequency of 10GHz, transmitting and receiving the microwave signal, converting the power of the microwave signal into a voltage signal, amplifying and collecting the voltage signal, then calculating the collected voltage signal to obtain a trace moisture result, and finally displaying trace moisture information to a user; comprises a power supply module 50, a data processing module 60, a signal acquisition module 70 and a microwave module 80; the input end of the power supply module 50 is connected with the lithium battery 40, and the output end of the power supply module 50 is connected with the data processing module 60, the signal acquisition module 70 and the microwave module 80 for supplying power; the power module 50 is configured to step down the 12V voltage of the lithium battery 40, convert the voltage into 3.3V, 3.4V, 5V, 5.4V and other voltages required by each chip module on the detection system circuit board 30, and electrically connect with each chip module through a wire to provide electric energy; the data processing module 60 is connected with the signal acquisition module 70 and receives the data sent by the signal acquisition module 70 to calculate the trace moisture, and meanwhile, the data processing module 60 displays the trace moisture calculation result in real time; the signal acquisition module 70 is connected with the microwave module 80 to receive the voltage signal of the microwave module 80 and output a digital signal to the data processing module 60 through signal conversion; the microwave module 80 is connected to the sample detection module 90, and detects the attenuation of the microwave signal power by transmitting and receiving the microwave signal, and converts the power values of the transmitting end and the receiving end into corresponding voltage values respectively and outputs the voltage values to the signal acquisition module 70;
the sample detection module 90 is used for placing the oil to be detected and transmitting and receiving microwave signals generated by the microwave module 80, and comprises a transmitting terminal antenna 901, a receiving terminal antenna 903 and a sample test container 902, wherein the transmitting terminal antenna 901 receives the microwave signals generated by the microwave module 80 and transmits the microwave signals to the air, the receiving terminal antenna 903 receives the microwave signals transmitted by the transmitting terminal antenna 901 and transmits the microwave signals to the microwave module 80, the microwave signals transmit through the sample to be detected in the sample test container 902 to be subjected to power attenuation, the sample test container 902 is used for placing the oil sample to be detected and fixing the volume of the sample to be detected, and the transmitting terminal antenna 901 and the receiving terminal antenna 903 are respectively installed at two ends of the sample test container 902.
The data processing module 60 is configured to receive voltage data converted from the microwave signal power, then calculate voltage difference information between the transmitting end and the receiving end to obtain a trace moisture result, and finally display the trace moisture information to a user, where the trace moisture result includes a minimum system 601 of a single chip microcomputer, a display module 602, a debugging serial port 603, and a function key 604;
the minimum system 601 of the single chip microcomputer is used for receiving 16-bit data sent by the signal acquisition module, wherein the 16-bit data is a group of digital signals converted from analog voltage signals acquired by the microwave module by the signal acquisition module; meanwhile, the single chip microcomputer minimum system calculates the 16-bit data through an internal trace moisture calculation program to obtain trace moisture information of the tested sample and sends the trace moisture information to a display screen module; the single chip microcomputer minimum system also selects program functions and debugs and programs through the function keys and the debugging serial port;
the display screen module 602 is used for dynamically displaying the value of the trace moisture of the tested sample, the residual electric quantity information of the lithium battery and the warning information;
the debugging serial port 603 is used for connecting the detection system circuit board with an external upper computer, debugging programs, programming programs and sending data of the detection system circuit board to the upper computer;
the function key 604 is used for selecting a function of a program in the minimum system 601 of the single chip microcomputer, and realizing a function of displaying a numerical value, recording a curve, warning and detecting the excessive moisture and debugging the program.
As shown in fig. 2, 13 and 14, the first type power supply pins (6, 17, 32, 33, 39, 52, 62, 72, 84, 95, 108, 121, 131, 144) of the microcontroller chip (U10) in the one-chip minimum system 601 are connected with 3.3V voltage (F103 _ 3.3V), and the second type power supply pins (16, 30, 31, 38, 51, 61, 71, 83, 94, 107, 120, 130, 143) are connected with ground (DGND). The clock input pin (23) is connected with a first pin (1) of the crystal oscillator (Y1), and the clock output pin (24) is connected with a second pin (2) of the crystal oscillator (Y1).
The first type data pins (56, 58, 59, 60, 63, 64, 65, 66, 67, 68, 77, 78, 79, 85, 86, 114, 115, 118, 119, 127) of the display screen module of the microcontroller chip (U10) are connected with the first type data pins (1, 2, 3, 4, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21) of the interface (P1) of the display screen module 602.
The second data pins (21, 22, 47, 48, 49) of the display screen module of the microcontroller chip (U10) are connected with the second data pins (29, 30, 31, 33, 34) of the display screen module 602 interface (P1).
And a display screen backlight control pin (46) of the microcontroller chip (U10) is connected with a backlight control pin (23) of the display screen module 602 interface (P1).
The first type debugging serial port pins (103, 109, 110, 133 and 134) and the second type debugging serial ports (101 and 102) of the microcontroller chip (U10) are connected with a debugging serial port 603.
Function key pins (26, 27, 28) of the microcontroller chip (U10) are connected to a function key module 604.
A voltage difference data receiving pin (75) of the microcontroller chip (U10) is connected with a data output pin (ADC _ SDO) of the ADC chip 704, and an SPI clock pin (74) is connected with a clock input pin (ADC _ SCK) of the ADC chip 704.
The battery charge detection pin (44) of the microcontroller chip (U10) is connected to a resistor series divider network (DIAN _ LIANG) at the input of the power module 50.
Specifically, as shown in fig. 2, the minimum system 601 of the single chip microcomputer realizes the following functions:
receiving operation information: the function keys 604 may send operating information of the user to the scm minimal system 601, including interface menu selection, trace detection function confirmation, and microcontroller chip reset. A microcontroller chip in the minimum system 601 of the single chip microcomputer can receive the operation information and execute corresponding functions;
receiving microwave signal power difference values ADC acquisition data of a transmitting end and a receiving end: the microwave signal power difference value ADC acquisition data of the transmitting end and the receiving end is 16-bit data which represents a microwave signal power attenuation value and is sent by an ADC chip 704, a microcontroller chip in the single chip microcomputer minimum system 601 receives the microwave signal power difference value data of the transmitting end and the receiving end through an SPI protocol, and the 16-bit binary data is converted into corresponding decimal data for calculating a trace moisture result;
calculating a trace moisture result: the micro-moisture result is a calculation result of a relational expression of ADC (analog to digital converter) acquired data and micro-moisture, the micro-controller chip receives 16-bit data sent by the ADC chip 704 and substitutes the 16-bit data into the relational expression of the ADC acquired data and the micro-moisture to obtain a micro-moisture detection result, and the relational expression of the ADC acquired data and the micro-moisture is a mathematical expression obtained through a pre-micro-moisture calibration experiment;
displaying system information: the system information comprises lithium battery electric quantity information, environment temperature information, trace moisture detection information, a trace moisture curve and moisture overproof warning information, and the microcontroller chip sends the system information to the display screen module 602 through a data interface to display the system information to users.
The signal acquisition module 70 is a signal acquisition module 70, configured to amplify and acquire the voltage signal converted from the microwave signal power, convert an analog signal into a digital signal, and send voltage data composed of the digital signal to the data processing module 60, and includes a first operational amplifier 701, a second operational amplifier 702, a subtractor 703, and an ADC chip 704;
the first operational amplifier 701 is used for performing adjustable multiple amplification on the output voltage of the first logarithmic detector 805 to enable the output voltage of the first operational amplifier 701 to be just 3.3V, and the output voltage of the first operational amplifier 701 is used as a reference value in the trace moisture calculation process, namely an unattenuated microwave power value;
specifically, as shown in fig. 2 and 9, the first power supply pin (5) of the first operational amplifier 701 (U14) is connected to the 3.4V voltage (ADC _ 3.4V), the second power supply pin (2) is connected to the ground (AGND), the non-inverting input pin (3) is connected to the detection voltage (FA _ SHE) output by the first logarithmic detector 805 (U8), and the output pin (1) outputs the amplified transmission terminal voltage (FA _ SHE _ 2) as the reference value for the calculation of the trace moisture result. The inverting input pin (4) is connected with a series voltage division network consisting of a precision adjustable resistor (R58) and a resistor (R52), the input end of the series voltage division network is connected with the output pin (1), and the other end of the series voltage division network is grounded (AGND).
The second operational amplifier 702 is configured to amplify the output voltage of the second logarithmic detector 809 by an adjustable multiple, so that the output voltage of the second operational amplifier 702 is 3.3V when the sample to be tested is not loaded in the sample testing container, that is, the difference between the output voltages of the first operational amplifier 701 and the second operational amplifier 702 is substantially 0;
specifically, as shown in fig. 2 and 10, the first power supply pin (5) of the second operational amplifier 702 (U15) is connected to the 3.4V voltage (ADC _ 3.4V), the second power supply pin (2) is connected to the ground (AGND), the non-inverting input pin (3) is connected to the detection voltage (JIE _ SHOU) output from the second logarithmic detector 809 (U9), and the output pin (1) outputs the amplified reception-side voltage (JIE _ SHOU _ 2) as a comparison value calculated from the trace moisture result. The inverting input pin (4) is connected with a series voltage division network consisting of a precision adjustable resistor (R57) and a resistor (R53), the input end of the series voltage division network is connected with the output pin (1), and the other end of the series voltage division network is grounded (AGND).
A subtractor 703 for subtracting the output voltages of the first operational amplifier 701 and the second operational amplifier 702, amplifying the subtracted voltage by 100 times, and outputting the amplified voltage to the ADC chip 704;
specifically, as shown in fig. 2 and 11, the first power supply pin (5) of the subtractor 703 (U17) is connected to the voltage of 3.4V (ADC _ 3.4V), the second power supply pin (2) is connected to ground (AGND), the non-inverting input pin (3) is connected to a series voltage-dividing network composed of a resistor (R62) and a resistor (R64), an input end of the series voltage-dividing network is connected to the transmitting terminal voltage (FA _ SHE _ 2) output by the first operational amplifier 701, and the other end is connected to ground (AGND). The inverting input pin (4) is connected with a series voltage division network consisting of a resistor (R63) and a resistor (R59), the input end of the series voltage division network is connected with the receiving end voltage (JIE _ SHOU _ 2) output by the second operational amplifier 702, and the other end of the series voltage division network is connected with the output pin (1). The subtractor 703 subtracts the transmitting terminal voltage (FA _ SHE _ 2) from the receiving terminal voltage (JIE _ SHOU _ 2) and amplifies the voltage difference by 100 times to output it to the ADC chip 704.
And the ADC chip 704 is configured to acquire a voltage signal output by the subtractor 703, convert the voltage signal into a corresponding 16-bit digital signal, and send data to the minimum system of the single chip microcomputer through an SPI protocol.
Specifically, as shown in fig. 2 and 12, the first power pin (1) of the ADC chip 704 (U18) is connected to a 3.4V voltage (ADC _ 3.4V), the first type power pins (3, 7) and the chip select pin (4) Are Grounded (AGND), the voltage input pin (2) is connected to a differential voltage filtered by a low pass filter composed of a resistor (R61) and a capacitor (C95), the data output pin (5) outputs a 16-bit data signal (ADC _ SDO) converted from the differential voltage, and the clock input pin (6) inputs an SPI communication protocol clock signal (ADC _ SCK).
The 16-bit data signal is binary number corresponding to decimal number from 0 to 65535, the conversion method from analog signal to digital signal is that the proportional relation obtained by dividing the input voltage of the voltage input pin (2) by the reference voltage (ADC _ 3.4V) is multiplied by 65535, the obtained data is the 16-bit digital signal corresponding to the analog signal, and finally the 16-bit data is sequentially output from high bit to low bit at the data output pin (5) according to the falling edge of the clock signal of the clock input pin (6).
The microwave module 80 is configured to generate a microwave signal with a frequency of 10GHz, filter and detect the power of the microwave signal, convert the power of the microwave signal into a voltage signal, and output the voltage signal to the signal acquisition module 70, where the microwave module 80 respectively outputs voltages converted from the powers of the microwave signals at the transmitting end and the receiving end to compare the two paths of signals, so as to obtain an attenuation value of the power of the microwave signal after passing through the oil product to be measured; the device comprises a voltage-controlled oscillator 801, a variable gain amplifier 802, a first band-pass filter 803, a first directional coupler 804, a first logarithmic detector 805, a strip line isolator 806, a second band-pass filter 807, a second directional coupler 808, a second logarithmic detector 809, a negative voltage power supply 810 and a precision adjustable resistor 811; the voltage-controlled oscillator 801 is used for generating a 10GHz microwave signal, the frequency of the microwave signal and the tuning voltage input to the voltage-controlled oscillator 801 have a corresponding relation, the corresponding relation refers to a curve of the relation between the output frequency and the tuning voltage given in a chip data manual of the voltage-controlled oscillator, and the range of the input tuning voltage can be selected according to the curve.
Specifically, as shown in fig. 2 and fig. 6, a first power pin (21) of a voltage-controlled oscillator 801 (U3) is connected to a voltage of 5V (HMC 512_ 5V), the first power pin (6, 7) is floating, the second power pin (5, 11) and the pins without electrical property (1, 2, 3, 8, 9, 10, 13, 14, 15, 16, 17, 18, 20, 22, 23, 24, 25, 26, 27, 28, 30, 31, 32) are both grounded (RFGND), a tuning voltage input pin (29) is connected to a voltage divided by a precision adjustable resistor (R7) and filtered by a low-pass filter composed of a resistor (R6) and capacitors (C98, C2), and at this time, the voltage-controlled oscillator 801 (U3) generates a 10GHz microwave signal and outputs the microwave signal through a radio frequency output pin (19).
The variable gain amplifier 802 is configured to amplify or attenuate the microwave signal output by the voltage controlled oscillator 801 by a controllable gain, so as to control the transmission power. The gain control voltage of the variable gain amplifier 802 is provided by a negative voltage power supply and is precisely adjusted through a precisely adjustable resistor to realize the change between-3.3V and-1V, and the gain value of the variable gain amplifier is changed between-2 dB and 16 dB.
Specifically, as shown in fig. 2 and 7, the first type power supply pins (19, 24) of the variable gain amplifier 802 (U7) are connected to a 5V voltage (HMC 996_ 5V), the second type power supply pins (3, 5, 14, 16) and the pins without electrical property (1, 2, 6, 8, 10, 11, 13, 17, 18, 20, 21, 22, 23) are all grounded (RFGND), the first gate control pin (7) and the second gate control pin (12) are connected to a series voltage division network composed of a resistor (R29) and a precision adjustable resistor (R30), the gain control pin (9) is connected to a series voltage division network composed of a precision adjustable resistor 811 (R32) and a resistor (R31), the radio frequency input pin (4) receives a microwave signal generated by the voltage controlled oscillator 801 (U3), and the radio frequency output pin (15) outputs a microwave signal after gain.
The first band pass filter 803 is used for band pass filtering the transmitting end microwave signal to reduce harmonic noise of the microwave signal.
And the first directional coupler 804 is used for coupling the microwave signal power on the transmission line of the transmitting end, and the microwave signal power obtained by coupling reflects the value of the microwave signal power of the transmitting end.
The first logarithmic detector 805 is configured to detect the power of the microwave signal output by the first directional coupler 804 and output a corresponding dc voltage to reflect the power of the microwave signal received by the first directional coupler, and further reflect the power of the microwave signal transmitted by the transmitting terminal.
Specifically, as shown in fig. 2 and 8, the first type power supply pins (13, 14, 15, 16) of the first logarithmic detector 805 (U8) are connected to a voltage of 3.3V (HMC 948 — 3.3V), the second type power supply pins (3, 6, 7) and the non-device attribute pins (1, 4, 5, 8, 9, 10, 12) are grounded (RFGND), the radio frequency input pin (2) receives a part of microwave power coupled from the microwave signal transmission path by the first directional coupler 804, and the detection output pin (11) is connected to a low pass filter composed of a resistor (R28) and a capacitor (C43) and then outputs a detection voltage (FA _ SHE).
The detection voltage output by the first logarithmic detector 805 (U8) and the microwave power received by the radio frequency input pin (2) are in a linear relation between-40 dBm and 0dBm, and the larger the received microwave power is, the larger the output detection voltage is, the variation range of the detection voltage (FA _ SHE) is from 1.1V to 1.7V.
The strip line isolator 806 is configured to isolate the reflected signal at the transmitting end, so that the reflected signal cannot return to the first directional coupler 804, and further ensure that the first logarithmic detector is not interfered by the reflected signal.
The second band pass filter 807 is used to perform band pass filtering on the microwave signal at the receiving end, so that the microwave signal is more pure.
And the second directional coupler 808 is configured to couple microwave signal power on the transmission line of the receiving end, where the microwave signal power obtained through coupling reflects a numerical value of the microwave signal power of the receiving end.
The second logarithmic detector 809 is configured to detect the power of the microwave signal output by the second directional coupler 807 and output a corresponding dc voltage to reflect the power of the microwave signal received by the second directional coupler, further reflect the power of the microwave signal received by the receiving end.
Specifically, as shown in fig. 2 and 8, the first type power supply pins (13, 14, 15, 16) of the second logarithmic detector 809 (U9) are connected to the 3.3V voltage (HMC 948_ 3.3V), the second type power supply pins (3, 6, 7) and the non-electrical-device-attribute pins (1, 4, 5, 8, 9, 10, 12) are all grounded (RFGND), the radio-frequency input pin (2) receives a portion of microwave power coupled from the microwave signal transmission path by the second directional coupler 808, and the detection output pin (11) is connected to the low-pass filter composed of the resistor (R28) and the capacitor (C44) to output the detection voltage (JIE _ SHOU).
The detection voltage output by the second logarithmic detector 809 (U9) is linear with the microwave power received by the rf input pin (2) between-40 dBm and 0dBm, and the detection voltage output is larger as the received microwave power is larger, the variation range of the detection voltage (JIE _ SHOU) is 1.1V to 1.7V.
The negative voltage power supply 810 is used to generate a-3.3V dc voltage to provide a negative voltage to the gain control terminal and the gate control terminal of the variable gain amplifier 802.
The precision adjustable resistor 811 is used to form a series voltage divider circuit to make the voltage output to the gain control terminal of the variable gain amplifier 802 vary from-3.3V to-1V.
Specifically, the input voltage of the gain control pin (9) of the variable gain amplifier 802 (U7) can be adjusted to change between-3.3V and-1V by the series voltage division network formed by the precise adjustable resistor 811 (R32) and the resistor (R31), so that the gain value of the variable gain amplifier 802 (U7) on the microwave signal changes between-2 dB and 16dB, and the adjustment of the microwave signal power is realized.
The upper shell 1 and the lower shell 2 of the equipment shell are of asymmetric structures, the matching surfaces of the upper shell 1 and the lower shell 2 are buckled in an internal-external staggered mode, and when the assembling positions of the upper shell 1 and the lower shell 2 are incorrect, the anti-reverse structure can prevent the equipment shell from being well matched. The upper shell 1 and the lower shell 2 are fixed by screws.
The upper shell 1 is used for fixing a detection system circuit board and reserving an opening for a structural member of the detection system circuit board, the opening of the upper shell 1 comprises a display screen module opening 3, a function key opening 4, a microwave module transmitting end opening 9 and a microwave module receiving end opening 10, and the upper shell also comprises a detection system circuit board fixing hole 5, an anti-reverse installation structure 6 and an upper shell and lower shell mounting hole 7;
The signal acquisition module 70 utilizes a first log detector 805 and a second log detector in a microwave moduleThe output voltage of the detector 809 is used as a signal processing and collecting object, the output voltages of the first logarithmic detector 805 and the second logarithmic detector 809 are respectively amplified by the first operational amplifier 701 and the second operational amplifier 702, when no sample to be tested is added, the output voltages of the first operational amplifier 701 and the second operational amplifier 702 are equal, when a sample to be tested containing water is added, the output voltage of the second logarithmic detector 809 is attenuated, the output voltage of the second operational amplifier 702 is also reduced, at the moment, the output voltage of the first operational amplifier 701 and the output voltage of the second operational amplifier 702 are different, the difference is made by the subtracter 703 and amplified by 100 times, the difference is input into the ADC chip 704 for voltage collection, and the relation between the output voltage and the input voltage of the subtracter 703 is V OUT ＝100*(V IN+ -V IN- ) In which V is OUT The voltage, V, input to the ADC chip 704 for the subtractor 703 IN+ Is the output voltage, V, of the first operational amplifier 701 IN- The ADC acquisition value of the ADC chip 704 for voltage acquisition for the output voltage of the second operational amplifier 702 has a range of 0-65535, if (V) IN+ -V IN- ) If Δ V is recorded, the relationship between the ADC acquisition value data and the voltage difference Δ V is
The invention also provides a detection method of the microwave transmission type high-precision online detection system for trace moisture in oil, which comprises the following steps:
the method comprises the steps of adding a tested oil product into a sample testing container 902, enabling the oil level height to reach a scale mark in the sample testing container 902, then starting a power switch of a detection system, generating a microwave signal with the frequency of 10GHz after the system is powered on, transmitting and receiving the microwave signal through a transmitting end antenna 901 and a receiving end antenna 903 to enable the microwave signal to be attenuated when the microwave signal transmits through the tested oil product, respectively detecting a transmitter and a receiver of a microwave module 80 through a first logarithmic detector 805 and a second logarithmic detector 809 to obtain a microwave signal power value transmitted by the transmitting end antenna 901 and a microwave signal power value received by the receiving end antenna 903 and output corresponding direct current voltage signals, amplifying the voltage signals corresponding to the microwave signal power values of the transmitter and the receiver through a first operational amplifier 701 and a second operational amplifier 702 to achieve the effect that the microwave signal is not attenuated when the microwave signal is not attenuated, gradually reducing the output voltage of the second operational amplifier 702, namely the microwave signal power voltage of the receiver microwave signal power when the microwave signal is attenuated, substituting the two voltage signals into a subtractor 703 circuit to achieve the effect that the micro-power attenuation data is obtained by further amplifying the micro-micro attenuation data, and finally displaying the micro-level of the micro-based on the micro-detection and the micro-quantity acquired by an ADC chip 602 to obtain the micro-based on the micro-scale detection.
Based on the foregoing embodiments, as shown in fig. 1, 2, 15 and 16, the following describes an application of the present invention:
firstly, configuring a standard sample with the moisture content of 0%, 0.003%, 0.005%, 0.006%, 0.01%, 0.012%, 0.014%, 0.016%, 0.018%, and 0.02% for detection test, placing the standard sample into a sample test container 902, starting a detection system power supply, refreshing the moisture detection result every 3500ms by a data processing module 60 through a display screen module 602 of the data processing module, and comparing an actual test result with a trace moisture detection function built in the data processing module 60, wherein the ADC acquisition value with the moisture content of 0% is 0, the ADC acquisition value with the moisture content of 0.003% is 367, the ADC acquisition value with the moisture content of 0.005% is 573, the ADC acquisition value with the moisture content of 0.006% is 1085, the ADC acquisition value with the moisture content of 0.01% is 1088, the ADC acquisition value with the moisture content of 0.012% is 4043, the ADC acquisition value with the moisture content of 0.014% is 52%, the ADC acquisition value with the moisture content of 0.016% is 1800.01%, the ADC acquisition error of 293% is 246%, and the ADC acquisition error of the ADC acquisition value of 0.02% is 246%, and the moisture content of the invention is found by the inventionThe interval is +/-10%, the interval between 0.01% and 0.02% is +/-2%, the resolution requirement of the trace moisture detection of the quenching oil is 0.01%, and the detection error of the method is +/-0.001%, so that the accuracy of a detection result is not influenced, and the high-precision trace moisture detection can be realized. The relational expression of the water content and the ADC acquisition value has four parameters of a =0.0121, b =8.674e-6, c = -0.01188, d = -7.095e-4, and the expression form is f (x) = ae b*x +ce d*x Where x represents the ADC acquisition value.
The invention has the advantages that:
(1) The whole size of the detection system is small, and the size of the equipment shell is 150mm multiplied by 90mm multiplied by 40mm; the lithium battery can be charged and used circularly, and can move flexibly without the limitation of a power line; the operation mode is simple, and the trace moisture detection result can be obtained in real time;
(2) The weak attenuation of microwave power is amplified by 100 times by adopting a subtractor circuit, a voltage signal is acquired by a 16-bit precision ADC chip, so that a detection system can sense a voltage difference value of 0.02mV between two detection voltages of a transmitter and a receiver, and meanwhile, the sensitivity and the precision of the detection system are improved by using a low-noise power supply and an optimized circuit topology design, the detection precision of trace moisture is +/-0.001%, and moisture below 0.02% can be detected;
(3) The detection mode of microwave transmission ensures that the oil product is not polluted, does not generate detection waste liquid, also ensures that a detection system is not corroded, and can be popularized to the measurement of trace moisture of various oil products.
Claims (2)
1. A microwave transmission type high-precision online detection system for trace moisture in oil comprises an upper shell (1) and a lower shell (2) which are buckled together to form an equipment shell (20), and is characterized in that a lithium battery (40) and a detection system circuit board (30) are mounted inside the equipment shell (20), and a sample detection module (90) is connected with the detection system circuit board (30) in a signal mode and located outside the equipment shell (20), wherein the detection system circuit board (30) is mounted inside the upper shell (1) through a positioning hole, the lithium battery (40) is mounted inside the lower shell (2), and the lithium battery (40) provides 12V direct current electric energy for the detection system circuit board (30);
the detection system circuit board (30) comprises a power supply module (50), a data processing module (60), a signal acquisition module (70) and a microwave module (80); the input end of the power supply module (50) is connected with the lithium battery (40), and the output end of the power supply module (50) is connected with the data processing module (60), the signal acquisition module (70) and the microwave module (80) for supplying power; the data processing module (60) is connected with the signal acquisition module (70) and receives data sent by the signal acquisition module (70) to calculate the trace moisture, and meanwhile, the data processing module (60) displays the calculation result of the trace moisture in real time; the signal acquisition module (70) is connected with the microwave module (80) to receive the voltage signal of the microwave module (80) and output a digital signal through signal conversion to be sent to the data processing module (60); the microwave module (80) is connected with the sample detection module (90), detects the attenuation of the microwave signal power by transmitting and receiving microwave signals, converts the power values of a transmitting end and a receiving end into corresponding voltage values respectively and outputs the voltage values to the signal acquisition module (70);
the sample detection module (90) comprises a transmitting end antenna (901), a receiving end antenna (903) and a sample test container (902), wherein the transmitting end antenna (901) receives microwave signals generated by a microwave module (80) and emits the microwave signals to the air, the receiving end antenna (903) receives the microwave signals emitted by the transmitting end antenna (901) and transmits the microwave signals to the microwave module (80), the microwave signals penetrate through a sample to be tested in the sample test container (902) to be subjected to power attenuation, the sample test container (902) is used for placing a sample to be tested and fixing the volume of the sample to be tested, and the transmitting end antenna (901) and the receiving end antenna (903) are respectively installed at two ends of the sample test container (902);
the data processing module (60) comprises a singlechip minimum system (601), a display screen module (602), a debugging serial port (603) and a function key (604);
the single chip microcomputer minimum system (601) is used for receiving 16-bit data sent by the signal acquisition module, and the 16-bit data is a group of digital signals converted from analog voltage signals acquired by the microwave module by the signal acquisition module; meanwhile, the single chip microcomputer minimum system calculates the 16-bit data through an internal trace moisture calculation program to obtain trace moisture information of the tested sample and sends the trace moisture information to a display screen module; the single chip microcomputer minimum system also selects program functions and debugs and programs through the function keys and the debugging serial port;
the display screen module (602) is used for dynamically displaying the value of the trace moisture of the tested sample, the residual electric quantity information of the lithium battery and the warning information;
the debugging serial port (603) is used for connecting the detection system circuit board with an external upper computer, carrying out program debugging and program programming and sending the data of the detection system circuit board to the upper computer;
the function key (604) is used for selecting the function of a program in the singlechip minimum system (601), and realizing the functions of displaying numerical values, recording curves, warning and detecting the excessive water content and debugging the program;
the signal acquisition module (70) comprises a first operational amplifier (701), a second operational amplifier (702), a subtracter (703) and an ADC chip (704);
the first operational amplifier (701) is used for amplifying the output voltage of the first logarithmic detector (805) by adjustable times, so that the output voltage of the first operational amplifier (701) is just 3.3V, and the output voltage of the first operational amplifier (701) is used as a reference value in the trace moisture calculation process, namely an unattenuated microwave power value;
the second operational amplifier (702) is used for amplifying the output voltage of the second logarithmic detector (809) by adjustable times, so that the output voltage of the second operational amplifier (702) is 3.3V when the sample to be tested is not loaded in the sample testing container, namely the difference value of the output voltages of the first operational amplifier (701) and the second operational amplifier (702) is 0;
a subtractor 703 for subtracting the output voltages of the first operational amplifier 701 and the second operational amplifier 702, amplifying the subtracted voltage by 100 times, and outputting the amplified voltage to an ADC chip 704;
the ADC chip (704) is used for collecting the voltage signal output by the subtracter (703), converting the voltage signal into a corresponding 16-bit digital signal and sending data to the single chip microcomputer minimum system through an SPI protocol;
the microwave module (80) comprises a voltage-controlled oscillator (801), a variable gain amplifier (802), a first band-pass filter (803), a first directional coupler (804), a first logarithmic detector (805), a strip line isolator (806), a second band-pass filter (807), a second directional coupler (808), a second logarithmic detector (809), a negative voltage power supply (810) and a precision adjustable resistor (811);
a voltage controlled oscillator (801) for generating a 10GHz microwave signal;
the variable gain amplifier (802) is used for amplifying or attenuating the microwave signal output by the voltage-controlled oscillator (801) by controllable gain so as to achieve the purpose of controlling the transmitting power; the gain control voltage of the variable gain amplifier (802) is provided by a negative voltage power supply and is precisely adjusted through a precise adjustable resistor to realize the change between-3.3V and-1V, and the gain value of the variable gain amplifier is changed between-2 dB and 16 dB;
a first band pass filter (803) for band pass filtering the transmitting end microwave signal to reduce harmonic noise of the microwave signal;
the first directional coupler (804) is used for coupling the microwave signal power on the transmission line of the transmitting end, and the microwave signal power obtained by coupling reflects the value of the microwave signal power of the transmitting end;
the first logarithmic detector (805) is used for detecting the microwave signal power output by the first directional coupler (804) and outputting corresponding direct-current voltage to reflect the power of the microwave signal received by the first directional coupler;
a strip line isolator (806) for isolating the reflected signal at the transmitting end from returning to the first directional coupler (804);
a second band-pass filter (807) for band-pass filtering the receiving-end microwave signal;
a second directional coupler (808) for coupling the microwave signal power on the transmission line of the receiving end;
the second logarithmic detector (809) is used for detecting the power of the microwave signal output by the second directional coupler (808) and outputting a corresponding direct-current voltage so as to reflect the power of the microwave signal received by the second directional coupler;
a negative voltage source (810) for generating a-3.3V DC voltage to provide a negative voltage to the gain control terminal and the gate control terminal of the variable gain amplifier (802);
the precision adjustable resistor (811) is used for forming a series voltage division circuit and enabling the voltage output to the gain control end of the variable gain amplifier (802) to change from-3.3V to-1V;
the first band-pass filter (803) and the second band-pass filter (807) are microstrip line devices, the 3dB bandwidth of the microstrip line devices is 9GHz-11 GHz, the center frequency of the microstrip line devices is 10GHz, the insertion loss at 10GHz is 0.7dB, the first band-pass filter (803) and the second band-pass filter (807) are structurally combined by adopting a step impedance line and a parallel coupling line, and the microstrip line devices are structurally characterized in that: an input port (1001), a first step impedance resonator (1002), an interdigital parallel coupling line (1003), a second step impedance resonator (1004) and an output port (1005) are sequentially connected, the input port of a first band-pass filter (803) is connected with a variable gain amplifier (802), the output port is connected with a first directional coupler (804), the input port of a second band-pass filter (807) is connected with a receiving terminal antenna (903), and the output port is connected with a second directional coupler (808);
the upper shell (1) and the lower shell (2) of the equipment shell adopt asymmetric structures, the matching surface of the upper shell (1) and the lower shell (2) adopts an inside-outside staggered buckling mode, and the upper shell (1) and the lower shell (2) are fixed by screws;
the upper shell (1) is used for fixing the detection system circuit board and reserving an opening for a structural part of the detection system circuit board, the opening of the upper shell (1) comprises a display screen module opening (3), a function key opening (4), a microwave module transmitting end opening (9) and a microwave module receiving end opening (10), and in addition, the upper shell also comprises a detection system circuit board fixing hole (5), an anti-reverse installation structure (6) and upper and lower shell mounting holes (7);
the lower shell (2) is used for fixing the lithium battery and reserving an opening for a lithium battery structural part, and the opening of the lower shell comprises a power switch opening (8), a lithium battery charging opening (11), an anti-reverse installation structure (6) and upper and lower shell mounting holes (7);
the signal acquisition module (70) utilizes the outputs of a first logarithmic detector (805) and a second logarithmic detector (809) in the microwave moduleThe output voltage is taken as a signal processing and collecting object, the output voltages of a first logarithmic detector (805) and a second logarithmic detector (809) are respectively amplified by a first operational amplifier (701) and a second operational amplifier (702), when no sample to be tested is added, the output voltages of the first operational amplifier (701) and the second operational amplifier (702) are equal, when a sample to be tested containing water is added, the output voltage of the second logarithmic detector (809) is attenuated, the output voltage of the second operational amplifier (702) is also reduced, the output voltage of the first operational amplifier (701) and the output voltage of the second operational amplifier (702) are different, the difference is made by a subtracter (703) and amplified by 100 times, the difference is input into an ADC chip (704) for voltage collection, and the relation between the output voltage of the subtracter (703) and the input voltage is V OUT ＝100*(V IN+ -V IN- ) In which V is OUT Is the voltage, V, input to the ADC chip (704) for the subtractor (703) IN+ Is the output voltage, V, of the first operational amplifier (701) IN- The output voltage of the second operational amplifier (702) is the ADC acquisition value range of the ADC chip (704) for voltage acquisition is 0-65535, if (V) IN+ -V IN- ) Recording as delta V, the relation between the ADC acquisition value data and the voltage difference delta V is
2. The detection method of the microwave transmission type high-precision on-line detection system for trace moisture in oil according to claim 1, comprising the following steps:
adding the oil to be detected into a sample testing container (902), enabling the oil level to reach the scale mark in the sample testing container (902), then starting a power switch of a detection system, generating a microwave signal with the frequency of 10GHz after the system is powered on, transmitting and receiving the microwave signal through a transmitting end antenna (901) and a receiving end antenna (903) to enable the microwave signal to be attenuated when transmitting the oil to be detected, respectively detecting a transmitter and a receiver of a microwave device module (80) through a first logarithmic detector (805) and a second logarithmic detector (809) to obtain the microwave signal power value transmitted by the transmitting end antenna (901) and the microwave signal power value received by the receiving end antenna (903) and outputting corresponding direct-current voltage signals, the voltage signals corresponding to the microwave signal power values of the transmitter and the receiver are amplified by the first operational amplifier (701) and the second operational amplifier (702) to realize that the two voltage signals have no voltage difference when the microwave signals are not attenuated, the output voltage of the second operational amplifier (702), namely the detection voltage of the microwave signal power of the receiver, is gradually reduced after the microwave signals generate power attenuation, the two voltage signals are differentiated and then amplified by a subtracter (703) circuit, the weak attenuation of the microwave power is further amplified to realize high-precision detection, the voltage signals representing the microwave signal power attenuation are acquired by a 16-bit ADC chip (704) to obtain high-precision data, and the data are sent to a singlechip minimum system (601) to be substituted into a relational expression of trace moisture calibrated in advance and an ADC acquisition value to obtain a trace moisture detection result, and finally, displaying the trace moisture information through a display screen module (602).
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