Contact type thermophysical parameter penetrometer and detection method

Abstract

The invention discloses a contact type thermophysical parameter penetrometer and a detection method, the detector comprises a main chip, a heating wire, a thermistor, a constant current source circuit, a sampling circuit, an interface filter circuit, an anti-aliasing filter circuit, an ADC, a load switch, a power supply module and a liquid crystal display, the load switch is arranged in a power supply circuit of the heating wire, and the thermistor is arranged in the power supply circuit of the heating wire. The load switch is in electric signal connection with the main chip, the thermistor serves as a sensor for detecting temperature, sensor signals are input into the main chip after being processed, and temperature information and the like are obtained after further processing of the main chip. The penetrometer is convenient to carry and use, can automatically identify a detection object and execute a corresponding detection process, is accurate in detection data, and is suitable for popularization and application.

Description

Technical Field

[0001] The present invention belongs to the technical field of geological exploration, and particularly relates to a contact type thermal property parameter penetrometer and a detection method Background Art

[0002] The thermal property parameters of rock and soil mainly include parameters such as thermal conductivity, specific heat capacity, and thermal diffusivity, which are basic data for various fields such as geothermal utilization and hot water resource development. Currently, the commonly used testing methods for rock and soil thermal property parameters mainly include laboratory measurement, numerical simulation, and on-site monitoring. However, the temperature detection equipment used in on-site monitoring is large, costly, complex in construction, requires on-site setup, is inconvenient to carry and use, thus reducing the detection efficiency and the popularization of the equipment Summary of the Invention

[0003] Technical Objective: Aiming at the above technical problems, the present invention provides a contact type thermal property parameter penetrometer and a detection method with a compact volume, convenient to carry and use, and high data detection accuracy

[0004] Technical Solution: To achieve the above technical objective, the present invention adopts the following technical solution

[0005] A contact type thermal property parameter penetrometer includes a penetrometer body with a probe at one end. Inside the penetrometer body, there are a main chip, a constant current source circuit and a sampling circuit, an interface filtering circuit, an anti-aliasing filtering circuit, an ADC, a load switch, and a power supply module. On the outer wall of the penetrometer body, there is a liquid crystal display screen electrically connected to the main chip, and inside the probe, there are a heating wire and a thermistor; among them

[0006] The working power supply of the heating wire is provided by the power supply module, and a load switch is provided in the power supply line of the heating wire. The load switch is electrically connected to the main chip and receives a control instruction sent by the main chip to control the on / off of the load switch

[0007] The thermistor is connected to the constant current source circuit and the sampling circuit. The constant current source circuit and the sampling circuit are used to detect the voltage signal across the thermistor and transmit the detected voltage signal to the interface filtering circuit. The input end of the anti-aliasing filtering circuit receives the signal output by the interface filtering circuit, and the output end is connected to the input end of the ADC. The ADC is used to perform analog-to-digital conversion on the received signal

[0008] The main chip is used to send a control instruction to control the on / off of the load switch, and to receive the signal output by the ADC and perform data processing to obtain temperature information

[0009] Preferably, a connector is provided at one end of the penetrometer body for switching and installing a flat probe or a probe-type probe. The probes designed in the present invention are mainly divided into two types that can be freely switched. The flat probe is mainly used to measure the thermal property parameters of the smooth surface of hard objects and fix immovable objects; the probe-type probe is mainly used to measure the thermal property parameters of objects or liquids that can be inserted with a probe.

[0010] Preferably, the power supply module includes a charging chip, a battery, and a dual-redundancy electronic switch. The battery is connected to the charging chip. The charging chip is also provided with a DC power charging interface and a USB interface. The power output terminal of the charging chip is connected to the load switch through the dual-redundancy electronic switch.

[0011] Preferably, the main chip uses a microcontroller of model ESP32, and the thermistor uses PT1000.

[0012] Preferably, the interface filter circuit is designed as a common-mode and differential-mode filter circuit. The anti-aliasing filter circuit uses a fourth-order Butterworth filter. The ADC uses an analog-to-digital conversion chip of model AD7193, and the load switch uses a switch of model BTS6143D.

[0013] A contact temperature detection method using the contact temperature penetrometer described above includes the following steps:

[0014] According to the shape of the object to be measured, install a flat probe or a probe-type probe at one end of the penetrometer body;

[0015] After the power supply is turned on, select the temperature detection button on the liquid crystal screen to start the temperature detection process;

[0016] The main chip sends a conduction instruction to the load switch to turn on the heating wire and monitors the state of the heating wire. The current flowing through the heating wire is displayed on the liquid crystal screen;

[0017] Place the probe body on the surface of the object to be measured, close to the object surface, or insert it into the internal preset depth of the object to be measured. The probe heats the object to be measured;

[0018] Due to the temperature change of the object to be measured, the thermistor causes a change in resistance. The voltage change across the thermistor is detected and sampled by the constant current source circuit and the sampling circuit, and is sequentially input into the interface filter circuit, the anti-aliasing filter circuit, and the ADC for processing. The ADC outputs the processed data to the main chip;

[0019] The main chip calculates the temperature of the object to be measured based on the data sent by the ADC, draws a curve of the temperature changing with time and displays it on the liquid crystal screen; the main chip calculates the thermal property parameters of the object to be measured based on the temperature data of the object to be measured;

[0020] When the temperature reaches the preset value, the main chip sends a disconnection instruction to the load switch, and the heating wire stops heating;

[0021] The main chip calculates the thermal physical property parameters of the object to be measured based on the temperature data of the object to be measured and displays them on the liquid crystal screen.

[0022] Preferably, it includes the following steps: The main chip determines the property of the object to be measured according to the data received after the heating wire is heated and the curve of the temperature of the object to be measured changing with time, and adjusts the heating current value of the heating wire according to the judgment result.

[0023] Beneficial effects: Due to the adoption of the above technical solution, the present invention has the following beneficial effects:

[0024] The contact type temperature sounding instrument designed by the present invention can heat substances such as rocks and soil layers, can read the change of the temperature of the current heating object with time, and realizes geophysical exploration measurements of different types of objects such as hard, soft objects and liquids by switching between flat plate type or probe type probes. The detector is powered by a lithium battery, is compatible with external power supply and charges the battery, and the battery life needs to be more than 1 day, which is convenient to carry and use. Brief Description of the Drawings

[0025] Figure 1 is a structural block diagram of a contact type temperature sounding instrument proposed by the present invention;

[0026] Figure 2 is an electronic circuit diagram of a common mode and differential mode filtering circuit;

[0027] Figure 3 is an electronic circuit diagram of a PT100 constant current source circuit and a sampling circuit;

[0028] Figure 4 is a structural schematic diagram of a detection part of a flat plate type probe / sensor;

[0029] Figure 5 is a structural schematic diagram of a probe type probe / sensor;

[0030] Figure 6 is Figure 5 the structural schematic diagram inside the probe in Detailed Embodiment

[0031] The embodiments of the present invention will be described in detail below with reference to the drawings.

[0032] The present invention proposes a contact type thermal physical property sounding instrument, which includes a hardware part and a software part. The hardware part includes a heating module, a sensor module, an analog input interface module, a control module, a display module and a power supply module; the software part is mainly used for functions such as data acquisition, data processing, storage, reading and control.

[0033] The specific hardware design performance indicators are as follows:

[0034] (1) Heating method: heating wire;

[0035] (2) Contact method: direct contact;

[0036] (3) Power supply voltage: 18650 lithium battery pack, 12V;

[0037] (4) Endurance capacity: 3000 mAh;

[0038] (4) Number of channels: heating * 1, temperature reading * 1;

[0039] (5) Sampling rate: 1 Hz - 4.8 K;

[0040] (6) Channel gain: 2.5 times gain;

[0041] (8) Measurement accuracy: +0.1 °C;

[0042] (9) Measurement range: -200 °C - 420 °C;

[0043] (10) Channel drift: +1 ppm / °C;

[0044] (11) Display method: liquid crystal display.

[0045] The specific software functions are as follows:

[0046] (1) It can automatically switch the voltage to achieve the heating function;

[0047] (2) Collect data in real time and display the temperature change over time;

[0048] (3) It can automatically analyze the results (thermal conductivity, specific heat capacity, etc.) according to requirements;

[0049] (4) By switching the probe, the difference and change in the thermal conductivity of the object can be realized, and it can be used to judge whether the object is complete or meets the requirements of heat insulation and heat conduction, etc.;

[0050] (5) Switching the probe can achieve the measurement of hard, soft objects and liquids;

[0051] (6) Automatically save the original data and the processed data; save editable graphics.

[0052] (7) There are instrument off buttons, start heating, switch probe, project number, data saving, reading and processing buttons, etc. on the interface; the interface can display the temperature change curve over time in real time.

[0053] I. Example

[0054] Figure 1An example of a contact thermal property parameter penetrometer is shown, including: an electric heating wire as a heating module, a PT100 that constitutes a temperature sensor, an interface filtering circuit, a PT100 constant current source circuit, a sampling circuit, an anti-aliasing filtering circuit, and an ADC that constitute an analog input interface circuit, an ESP32 main chip, a load switch, and a dual-redundancy electronic switch, etc. that constitute a control module.

[0055] In this example, the heating method is by electric heating wire, and the 12V DC power supply is converted to 9V for power supply. The load switch provides protection for the battery and is controlled by the main chip at the same time. After the main chip issues a heating task through the LCD screen, it controls the load switch to turn on and supply power to the heating wire. The PT100 and the metal part of the heating wire are completely isolated to ensure that the actual temperature of the object to be measured is measured, and the influence of the heating wire on the PT100 is minimized.

[0056] The main chip uses the ESP32 produced by Espressif Systems, which is a high-performance and low-power microcontroller with rich functions and a wide range of application scenarios. It uses a dual-core 32-bit LX6 microprocessor with a maximum operating frequency of up to 240MHz, supporting high-performance computing and multitasking. It is equipped with 520KB of SRAM and 448KB of ROM, and supports external 4MB of SPI Flash and 8MB of PSRAM for expanding the memory capacity. At the same time, it includes an LCD interface. Its functions and performance are sufficient to meet the usage requirements. Five function keys are reserved, namely the down, up, left, right, and confirm keys.

[0057] The power supply module uses a 12V lithium battery and an external 12V compatible power supply method, and the battery power is displayed on the LCD screen.

[0058] 1. Analog Input Interface Module

[0059] 1.1 Interface Filtering Circuit

[0060] The interface filtering circuit is designed as a common-mode and differential-mode filtering circuit.

[0061] After the sensor signal enters the device, it first passes through the common-mode and differential-mode filtering circuit and then goes to the subsequent conditioning circuit.

[0062] As Figure 2 shown, the entire common-mode and differential-mode filtering circuit is mainly composed of TVS protection diodes, common-mode inductors, differential-mode inductors, common-mode capacitors, and differential-mode capacitors.

[0063] TVS Protection Diode: D5 is mainly used to prevent high-voltage pulses generated during the moment when the sensor is inserted with electricity from damaging the subsequent devices. The TVS protection diode will respond to the high-voltage pulses in a timely manner and clamp them to a non-damaging voltage range that the subsequent devices can accept.

[0064] Common-mode inductor: The main function of the L3 common-mode inductor is to suppress the common-mode interference on the sensor cable. When the common-mode interference on the cable passes through the L3 common-mode inductor, the common-mode inductor presents a high impedance state, and the common-mode interference returns to the source end due to its blocking effect.

[0065] Differential-mode inductor: The main functions of the L1 and L5 differential-mode inductors are to suppress the differential-mode interference on the sensor cable. When the differential-mode interference passes through the differential-mode inductor, the differential-mode inductor presents a high impedance state, and the differential-mode interference returns to the source end due to its blocking effect.

[0066] Common-mode capacitor: The main functions of the C16 and C54 common-mode capacitors are to filter the common-mode interference on the sensor cable to the housing. When the common-mode interference on the cable passes through the C16 and C54 common-mode capacitors, since the L3 common-mode inductor has a high impedance and the common-mode capacitor has a low impedance, part of the common-mode interference will return to the housing of the device through the common-mode capacitor, and part will return to the interference source.

[0067] Differential-mode capacitor: The main functions of the C34 and C37 differential-mode capacitors are to filter the differential-mode interference on the sensor cable to the ground of the sensor itself. When the differential-mode interference passes through the differential-mode capacitor, since the capacitor has a low impedance to the differential-mode interference, the differential-mode interference is filtered to its own ground by the capacitor.

[0068] 1.2, PT1000 constant current source circuit and sampling circuit

[0069] The circuit supports 2-wire / 3-wire / 4-wire input. This invention designs a handheld device. Due to the short wiring and small wire resistance, the 2-wire connection method is adopted, as Figure 3 shown. It is powered by a 1mA constant current source and buffered and amplified for the subsequent circuit.

[0070] 1.3, Filter

[0071] A fourth-order Butterworth filter is adopted, with a cut-off frequency of 10Hz (3Db).

[0072] 1.4, Selection of ADC analog-to-digital conversion chip

[0073] In this example, the analog-to-digital conversion chip with the model AD7193 is selected, a low-noise complete analog front end suitable for high-precision measurement applications. It integrates a low-noise, 24-bit Σ-Δ analog-to-digital converter (ADC). The on-chip low-noise gain stage means that small signals can be directly input into the ADC.

[0074] This device can be configured for four-channel differential input or eight-channel pseudo-differential input. The on-chip channel sequencer can enable multiple channels simultaneously, and the AD7193 performs conversions on the enabled channels in sequence, simplifying communication with the device. The on-chip 4.92 MHz clock can be used as the clock source for the ADC; alternatively, an external clock or crystal oscillator can also be used. The output data rate of this device can vary in the range of 4.7 Hz to 4.8 kHz.

[0075] This device has a very flexible digital filter, including a fast settling option. Variables such as the output data rate and settling time depend on the selected option. The AD7193 also includes a zero-delay option. Its operating power supply voltage is from 3V to 5.25V, and the power consumption is 4.65 mA, which is very suitable for battery applications.

[0076] A strain measurement system built with the AD7193. The AD7193 is a low-noise, low-drift 24-bit Σ-Δ ADC with an on-chip PGA and driver. This device integrates most system building blocks on the chip, thus simplifying the design of strain measurement. The AD7193 can maintain good performance within the full output data rate range of 4.7 Hz to 4.8 kHz and can be used in strain measurement systems operating at low speeds as well as high-speed strain measurement systems.

[0077] 2. Heating wire power supply circuit

[0078] The load switch selects the Infineon BTS6143D, which has an 8A current output capacity to meet the requirement of the instantaneous current at startup, thus protecting the battery.

[0079] It has short-circuit protection, overheat protection, overvoltage and overcurrent protection; at the same time, it has load coil demagnetization protection (heating wire demagnetization).

[0080] At the same time, the main chip can perform status monitoring. When the user starts heating, the MUC issues an instruction to turn on the load power supply and monitor the load status.

[0081] 3. Power system design

[0082] Considering that the heating wire is heated frequently, which places too much burden on the battery and the battery life can only meet one day at most, a charging circuit is designed. The circuit includes a dual-redundancy circuit that can perform USB charging / supplying power, external charging / supplying power. At the same time, USB can export the data stored in the storage chip to the computer.

[0083] The power system design follows the following points:

[0084] (1) It is powered by a 12V lithium battery, compatible with external power supply, can charge the lithium battery, and the 12V voltage can also be easily converted into voltages such as 9V, 5V, 3.3V, 2.5V, etc.

[0085] (2) Lithium battery charging requires detection, or the indicator light outputs to indicate a full charge signal.

[0086] 4. Detection function design

[0087] The contact thermal property parameter detector designed by the present invention can display the current and voltage of the heating function, time, and measurement sample number in real time on the liquid crystal screen, and adopt the model information of the probe, etc.

[0088] The data is saved in the exec format. One file contains the number of a measurement sample, the temperature data over time, and the finally calculated data.

[0089] It can achieve the following functions:

[0090] (1). Quickly and easily measure the thermal conductivity, specific heat capacity, and thermal diffusivity of various types of samples.

[0091] (2). According to the types of samples and measurement temperatures, appropriate sensors can be selected. One is a probe for hard geophysical flat plate tests with a flat detection part structure. As Figure 4 shown, the flat structure is internally provided with a resistance wire and a pt100 sensor, and the resistance wire and pt100 are isolated and separated, and the spacing can be set to 5 mm. One is a probe for measuring objects or liquids with a long and narrow needle-like detection part structure. As Figure 5 and Figure 6 shown, it includes a probe, a clamping device one, a clamping device two, and a fixed needle cap. One end of the probe is provided with a conical needle tip, and the other end passes through the fixed needle cap and is fixed by two clamping devices. The resistance wire and the pt100 sensor are arranged inside the probe. The flat plate probe requires the object surface to be smooth, and the probe type probe requires the object to be insertable inside with a probe. One end of both probes connected to the penetrometer body can be designed to be detachably installed on the connector provided on the penetrometer body through an aviation plug, and the connector is adapted to the aviation plug for convenient plugging and unplugging for switching.

[0092] (3). Liquid crystal display screen, and the heating curve can be directly observed during measurement.

[0093] (4). The heating curve is displayed in time logarithm, and the linearity of the measured value can be confirmed.

[0094] (5). Automatically judge the appropriate heating current value of the sample. mainly through the data collected by trial heating, the background automatically gives a preliminary judgment and makes automatic adjustment to achieve automatic judgment of the appropriate heating current value.

[0095] (6) After automatically determining that the sample temperature is stable, measurements are taken. That is, if the heating curve has basically reached a horizontal and unchanging state, it indicates that the temperature of the sample has reached equilibrium. The chip calculates the change in temperature over time and uses the developed software and relevant calculation formulas for thermal physical properties, such as the change in temperature per unit time or the slope of the heating curve, to analyze the thermal conductivity or heat insulation performance of the object under test, etc.

[0096] The above has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the above embodiments do not limit the present invention in any form. Any technical solutions obtained by means of equivalent replacement or equivalent transformation fall within the protection scope of the present invention.

Claims

1. A contact type thermal property parameter probe, comprising a probe body with a probe at one end, characterized in that: The main chip, constant current source circuit and sampling circuit, interface filter circuit, anti-aliasing filter circuit, ADC, load switch and power supply module are arranged inside the probe body, and a liquid crystal screen for connecting the electrical signal to the main chip is arranged on the outer wall of the probe body, and a heating wire and a thermistor are arranged inside the probe; wherein, The working power supply of the heating wire is provided by the power supply module. A load switch is provided in the power supply circuit of the heating wire. The load switch electrical signal is connected to the main chip and receives the control instruction of the main chip to control the on and off of the load switch. The thermistor is connected to a constant current source circuit and a sampling circuit, the constant current source circuit and the sampling circuit are used to detect the voltage signal at both ends of the thermistor and transmit the detected voltage signal to the interface filter circuit, the input end of the anti-aliasing filter circuit receives the signal output by the interface filter circuit, and the output end is connected to the input end of the ADC, and the ADC is used to perform analog-to-digital conversion on the received signal; The main chip is used to send a control instruction to the load switch to control the on and off of the load switch, and is used to receive the signal output by the ADC and perform data processing to obtain temperature information.

2. The contact type thermal property parameter probe according to claim 1, characterized in that: A connector is provided at one end of the probe body for switching between a flat-plate probe and a probe-type probe.

3. The contact type thermal property parameter probe according to claim 1, characterized in that: The power supply module includes a charging chip, a battery and a dual redundant electronic switch. The battery is connected to the charging chip. The charging chip is also provided with a DC power charging interface and a USB interface. The power output end of the charging chip is connected to the load switch through the dual redundant electronic switch.

4. The contact type thermal property parameter probe according to claim 1, characterized in that: The main chip adopts a microcontroller of model ESP32, and the thermistor adopts PT100.

5. The contact type thermal property parameter probe according to claim 1, characterized in that: The interface filter circuit is designed as a common-mode differential-mode filter circuit, the anti-aliasing filter circuit adopts a fourth-order Butterworth filter, the ADC adopts an analog-to-digital conversion chip of model AD7193, and the load switch adopts a switch of model BTS6143D.

6. A contact type thermal physical property parameter detection method, using the contact type thermal physical property parameter probe according to claim 1, characterized in that: The following steps are involved: According to the shape of the object to be measured, a flat probe or a probe probe is installed at one end of the probe body; After the power supply is turned on, select the temperature detection button on the LCD screen to start the temperature detection process; The main chip sends a conduction command to the load switch to connect the heating wire and monitor the status of the heating wire. The current flowing through the heating wire is displayed on the LCD screen. The probe body is placed on the surface of the object to be measured or inserted into the object to be measured to a preset depth, and the probe heats the object to be measured; The thermistor changes its resistance due to the temperature change of the object being measured. The voltage change at both ends of the thermistor is detected and sampled by the constant current source circuit and the sampling circuit, and is input into the interface filter circuit, the anti-aliasing filter circuit and the ADC for processing in sequence. The ADC outputs the processed data to the main chip. The main chip calculates the temperature of the object under test based on the data sent by the ADC, draws a curve of temperature change over time and displays it on the LCD screen; When the temperature of the object under test reaches equilibrium, the main chip sends a disconnection command to the load switch, and the heating wire stops heating; The main chip calculates the thermal physical parameters of the object under test based on the temperature data of the object under test and displays them on the LCD screen.

7. A contact type thermal physical property parameter detection method according to claim 6, characterized in that: The method comprises the following steps: the main chip judges the property of the object under test according to the data received after the heating wire is heated and the curve of the temperature change of the object under test over time, and adjusts the heating current value of the heating wire according to the judgment result.

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