CN108195282B - Ice layer thickness measuring device based on piezoresistive sensor - Google Patents
Ice layer thickness measuring device based on piezoresistive sensor Download PDFInfo
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- CN108195282B CN108195282B CN201711403374.8A CN201711403374A CN108195282B CN 108195282 B CN108195282 B CN 108195282B CN 201711403374 A CN201711403374 A CN 201711403374A CN 108195282 B CN108195282 B CN 108195282B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B7/00—Measuring arrangements characterised by the use of electric or magnetic techniques
- G01B7/02—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring length, width or thickness
- G01B7/06—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring length, width or thickness for measuring thickness
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Abstract
The invention relates to an ice layer thickness measuring device, in particular to an ice layer thickness measuring device based on piezoresistive sensors, and belongs to the technical field of automatic detection. The technical problems that a contact type ice layer thickness measuring device or a sensor in the prior art is complex in structure or large in measuring error and the like are solved. The device comprises a piezoresistive sensor, a chip selection circuit, a microcontroller, a resistance conversion circuit, a power circuit and a shell. The independent piezoresistive sensors are fixed on the surface of the shell at equal intervals, and the acting force of air, an ice layer or water under ice on the piezoresistive sensors is converted into the change of resistance values. The microcontroller controls the chip selection circuit to sequentially gate a single channel of piezoresistive sensors. The resistance conversion circuit converts the resistance value of the pressure resistance sensor into a voltage value to be output. And the microcontroller measures and compares the voltage value of each path, determines the positions of the upper interface and the lower interface of the ice layer and calculates the thickness of the ice layer. The device has the advantages of simple structure, stability, reliability, convenience in installation and maintenance and the like.
Description
Technical Field
The invention relates to an ice layer thickness measuring device, in particular to an ice layer thickness measuring device based on piezoresistive sensors, and belongs to the technical field of automatic detection.
Background
In the fields of weather forecast, ice flood prevention and control, facility structure health monitoring and the like, the change condition of the ice layer thickness is an important environmental parameter to be measured. In order to measure the thickness of the ice layer, one has to drill a hole for ice and measure the thickness of the ice layer using a ruler. Although the manual measurement method is accurate in measurement, the method is time-consuming, labor-consuming and high in danger, and the change of the thickness of the ice layer cannot be continuously monitored in real time.
Later, several contact ice thickness measurement techniques and devices were followed. Chinese patent (201210139060.2) discloses a dual-system ice layer thickness measuring device, which uses two sets of probes capable of moving up and down to clamp the ice layer, and calculates the thickness of the ice layer according to the moving distance of the two probes. Although the method has high measurement accuracy, the structure is complex, the measuring range is small, and the installation and the maintenance are difficult. Chinese patent (200410012164.2) and chinese patent (200510012794.4) disclose conductive and capacitive ice thickness sensors, respectively, which calculate the thickness of an ice layer by determining the position of the upper and lower interfaces of the ice layer from the differences in resistance and capacitance due to air, ice and water. However, since the electrical characteristics such as the conductivity and dielectric constant of air and ice are very similar, both methods cannot accurately determine the position of the upper interface of the ice layer, and thus cannot accurately measure the thickness of the ice layer.
Disclosure of Invention
The technical problem to be solved by the invention is to provide an ice layer thickness measuring device based on a piezoresistive sensor aiming at the defects and shortcomings of a contact type ice layer thickness measuring device or sensor in the background technology, and the ice layer thickness measuring device can clearly distinguish the positions of an upper interface and a lower interface of an ice layer by comparing the change of resistance values caused by the difference of acting forces generated by air on ice, the ice layer and water under ice on the piezoresistive sensor, so that the thickness of the ice layer can be accurately calculated.
The invention is realized by adopting the following technical scheme:
an ice layer thickness measuring device based on a piezoresistive sensor comprises the piezoresistive sensor, a chip selection circuit, a microcontroller, a resistance conversion circuit, a power circuit and a shell;
a plurality of independent piezoresistive sensors are fixed on the outer surface of the shell at equal intervals; the chip selection circuit, the microcontroller, the resistance conversion circuit and the power circuit are all positioned in the shell; the chip selection circuit comprises a plurality of chip selection switches which are connected through a data bus; each piezoresistive sensor is provided with two pins, and the number of the chip selection switches is consistent with the total number of the pins of all the piezoresistive sensors; each pin of the piezoresistive sensor is connected with the input end of one chip selection switch; the output ends of all chip selection switches connected with the first pin of the piezoresistive sensor are connected together to form a common end; the output ends of all chip selection switches connected with the second pin of the piezoresistive sensor are connected together to form another common end; the two public ends are respectively connected with the two input ends of the resistance conversion circuit; the output end of the resistance conversion circuit is connected with a pin with an analog-to-digital conversion function on the microcontroller; the microcontroller is connected with the chip selection circuit through a data bus; the power supply circuit respectively supplies power to the chip selection circuit, the microcontroller and the resistance conversion circuit.
The principle of the invention is as follows: in winter, the low temperature can cause the phenomenon of freezing of rivers, lakes and the like, so that three media of an ice layer, air on the ice and water under the ice can be formed. If a hole is made in the ice surface, the device of the present invention is placed. When the ice surface is frozen again and frozen, the medium around the device is air, an ice layer and water under the ice in sequence from top to bottom. In general (excluding high winds and high waves), the force between the ice layer and the piezoresistive sensors is much greater than the force of air and water under ice on the piezoresistive sensors. The resistance of the piezoresistive sensor becomes smaller as the external force increases. Therefore, the resistance of a piezoresistive sensor in a layer of ice is much less than the resistance of a piezoresistive sensor in air and water under ice. Then, if in order from top to bottom, the upper interface of the ice layer is located where the resistance of the adjacent piezoresistive sensor changes from large to small. The lower interface of the ice layer is located where the resistance of the adjacent piezoresistive sensor changes from small to large. The microcontroller controls the chip selection circuit, the resistance conversion circuit is used for sequentially measuring and comparing the piezoresistive sensors in each channel, the positions of the upper interface and the lower interface of the ice layer can be determined, and the thickness of the ice layer can be calculated according to the positions of the upper interface and the lower interface.
Further, the housing is made of a low temperature resistant plastic material; the chip selection circuit, the microcontroller, the resistance conversion circuit and the power circuit are sealed in the shell, and waterproof treatment is carried out; the piezoresistive sensor is positioned outside the shell and is subjected to corrosion prevention treatment.
Compared with the prior art, the ice layer thickness calculating device has the advantages of simple structure, stability, reliability, convenience in installation and maintenance, and capability of clearly distinguishing the positions of the upper interface and the lower interface of the ice layer, so that the thickness of the ice layer can be accurately calculated.
Drawings
FIG. 1 is a schematic diagram of an ice layer thickness measurement device based on piezoresistive sensors.
Fig. 2 is a schematic diagram of a resistance switching circuit.
Fig. 3 is an overall effect diagram.
The sensor comprises a piezoresistive sensor 1, a chip selection circuit 2, a microcontroller 3, a resistance conversion circuit 4, a power supply circuit 5, a shell 6, air 7, an ice layer 8, water ice 9, a chip selection switch 10, a current limiting resistor 11 and an operational amplifier 12.
Detailed Description
The following describes embodiments of the present invention in further detail with reference to the accompanying drawings.
The piezoresistive pressure sensor comprises a piezoresistive pressure sensor 1, a chip selection circuit 2, a microcontroller 3, a resistance conversion circuit 4, a power supply circuit 5 and a shell 6, and is shown in figure 1.
A plurality of independent piezoresistive sensors 1 are fixed on the outer surface of the shell 6 at equal intervals. The chip selection circuit 2, the microcontroller 3, the resistance conversion circuit 4 and the power supply circuit 5 are all located inside the shell 6. The chip selection circuit 2 comprises a plurality of chip selection switches 10, and the chip selection switches 10 are connected through a data bus. Each piezoresistive sensor 1 is provided with two pins, and the number of the chip selection switches 10 is consistent with the total number of the pins of all the piezoresistive sensors 1. Each pin of the piezoresistive sensor 1 is connected with the input end of one chip selection switch 10 through a through hole on the shell 6. The output ends of all chip select switches 10 connected to the first pin of piezoresistive sensor 1 are connected together to form a common end; the outputs of all chip select switches 10 connected to the second coil pin of piezoresistive sensor 1 are connected together to form another common terminal. The two common terminals are connected to the two input terminals of the resistance conversion circuit 4, respectively. The output end of the resistance conversion circuit 4 is connected with a pin with an analog-to-digital conversion function on the microcontroller 3. The microcontroller 4 is connected to the chip selection circuit 2 via a data bus. The power supply circuit 5 respectively supplies power to the chip selection circuit 2, the microcontroller 3 and the resistance conversion circuit 4.
The piezoresistive sensor 1 is a sensor that can convert an external force into a change in resistance value. In order to realize the measurement of the thickness of the ice layer, a plurality of independent piezoresistive sensors 1 are required to be fixed on the outer surface of the shell 6 at equal intervals. The number of piezoresistive sensors 1 is related to the measuring range and the measuring accuracy, as shown in formula 1.
Assuming that the measuring range to be measured is 2 meters and the measuring precision is 1cm, the total number of the piezoresistive sensors 1 is 200. The piezoresistive sensor 1 can be made of FSR from Interlink Electronics＠The 400 short tail sensor (FSR 400 for short) has a sensitive layer diameter of 5mm, a total length including the lead wires of 20mm, and a minimum driving force of 0.2N. The front side of the FSR400 is a sensitive layer for external force and needs to be in contact with the outside. The back of the FSR400 is a sticker layer that may be adhered to the outer surface of the housing 6 by an adhesive. The pin of the FSR400 may be bent to connect with the input of the chip select switch 10 of the chip select circuit 2 through a via in the housing 6.
The chip selection circuit 2 is used for gating or disconnecting each channel of piezoresistive sensors 1, so that the resistance conversion circuit 4 only acquires data of a single channel of piezoresistive sensors 1 at the same time. The chip select circuit 2 can be implemented using a serial control switch chip ADGS1412 of ANALOG DEVICES, inc. The ADGS1412 includes four separate single pole, single throw switches, i.e., four chip select switches 10. Since the FSR400 has two pins, each ADGS1412 can connect two FSRs 400. Thus, the number of ADGS1412 required is half of the total amount of FSR 400. The ADGS1412 supports SPI data bus control, and thus, a plurality of ADGS1412 are connected by an SPI bus.
The resistance conversion circuit 4 is a resistance/voltage conversion circuit that converts a change in the resistance value of the piezoresistive sensor 1 into a change in the voltage value. The resistance switching circuit 4 is composed of a current limiting resistor 11 and an operational amplifier 12, as shown in fig. 2. The resistance value of the current limiting resistor 11 is the same as the resistance value of the piezoresistive sensor 1 in an unstressed state. The operational amplifier 12 may be a single-path micro power operational amplifier MAX4091 available from MAXIM corporation. One input end of the resistance conversion circuit 4 is connected with the 3.3V output by the power circuit 5, and the other input end is connected with one end of the current limiting resistor 11. The other end of the current limiting resistor 11 is connected to ground. The output terminal of the operational amplifier 12 is connected to the negative input terminal of the operational amplifier 12 to form a voltage follower. The positive input terminal of the operational amplifier 12 is connected to the non-ground terminal of the current limiting resistor 11. The output terminal of the resistance conversion circuit 4 is the output terminal of the operational amplifier 12. When the chip selection circuit 2 gates a certain path of piezoresistive sensor 1, the piezoresistive sensor 1 and the current limiting resistor 11 form a series circuit. When the external force causes the resistance of the piezoresistive sensor 1 to decrease, the current flowing through the piezoresistive sensor 1 and the current limiting resistor 11 increases, and the voltage difference across the current limiting resistor 11 increases. Therefore, the larger the external force, the larger the voltage (i.e., the voltage due to the piezoresistive sensor 1) output by the resistance conversion circuit 4. Since the force of ice layer 8 on piezoresistive sensor 1 is much greater than the force of air 7 and water under ice 9 on piezoresistive sensor 1, the voltage induced by piezoresistive sensor 1 in ice layer 8 is greater than the voltage induced by piezoresistive sensor 1 in air 7 and water under ice 9. In a normal case (excluding the case of high winds and high waves), the upper interface of the ice layer 8 is located at a place where the voltage caused by the adjacent piezoresistive sensor 1 changes from small to large in the order from top to bottom. The lower interface of ice layer 8 is located where the voltage across the adjacent piezoresistive sensor 1 decreases from large to small.
The microcontroller 3 is a control center of the whole device, and not only controls the chip selection circuit 2 to sequentially gate the piezoresistive sensors 1 from top to bottom, but also reads a voltage value caused by each channel of piezoresistive sensors 1 through the resistance conversion circuit 4. The microcontroller 3 may be a microcontroller of Texas instruments, USACC1310 with 48MHz Cortex integrated therein@An M3 microcontroller, a 12-bit analog-to-digital converter and an ultra-low power RF transceiver, and also has an SPI synchronous serial interface, supporting an SPI data bus. The CC1310 is connected with the chip selection circuit 2 built by the ADGS1412 through an SPI data bus.
The power supply circuit 5 is used for supplying power to the chip selection circuit 2, the microcontroller 3 and the resistance conversion circuit 4, and preferably utilizes the power conversion chips LM2575 and LM1117 to realize voltage conversion and output 5V and 3.3V.
The shell 6 is a framework of the whole device, is made of low-temperature-resistant plastic materials and is used for fixing the piezoresistive sensor 1, the chip selection circuit 2, the microcontroller 3, the resistance conversion circuit 4 and the power circuit 5. Wherein piezoresistive sensor 1 is fixed to the outer surface of housing 6. The chip selection circuit 2, the microcontroller 3, the resistance conversion circuit 4, and the power supply circuit 5 are fixed inside the housing 6. The housing 6 is preferably made of a low temperature resistant Polyethylene (PE) material. Since the piezoresistive sensor 1 needs to be in contact with the outside, the surface of the piezoresistive sensor 1 can be coated with epoxy resin to form an anti-oxidation layer, thereby preventing the piezoresistive sensor 1 from being oxidized and corroded by the outside. The inside of shell 6 need do water repellent, and usable epoxy pours, ensures that chip selection circuit 2, microcontroller 3, resistance conversion circuit 4, power supply circuit 5 keep apart with water.
The length of the housing 6 and the number of piezoresistive sensors 1 need to be designed according to the maximum thickness of the ice layer 8 to be measured. The length of the shell 6 and the distribution range of the piezoresistive sensors 1 need to exceed the maximum thickness of the ice layer 8 to be measured, and the piezoresistive sensors 1 are ensured to be distributed in the air 7, the ice layer 8 and the water under ice 9 respectively.
The ice layer thickness measuring device of the invention is mainly suitable for automatically measuring the ice layer thickness of the ice layer of rivers, lakes or reservoirs as shown in figure 3.
The technical solution of the present invention will be further described below by referring to a specific example.
The embodiment is that the device is used for measuring the thickness of the ice layer of the lake:
before measurement, the device needs to extend into an ice cave which is chiseled in advance and is fixed on the ice surface through an external bracket (such as wood or a scaffold and the like), and ensures that the piezoresistive sensors 1 are respectively distributed in air 7, an ice layer 8 and ice water 9 after the ice cave is frozen and frozen again.
During measurement, the microcontroller firstly controls the chip selection circuit 2 to sequentially gate the chip selection switches 10 connected with two pins of the piezoresistive sensor 1 to be measured from top to bottom through the SPI data bus, and switches off other chip selection switches 10. Then, the microcontroller 3 measures the voltage converted by the resistance conversion circuit 4.
After the measurement is completed, the microcontroller 3 compares the voltage values of each path from top to bottom. Since in the normal case (excluding the case of high winds and waves) the voltage value induced by piezoresistive sensors 1 in the layer of ice 8 is greater than the voltage value induced by piezoresistive sensors 1 in the air 7 and the water under ice 9. When the voltage value of a certain path is larger than that of the previous path, the piezoresistive sensor 1 of the path is considered to be in the ice layer 8. Here also considered as the upper interface of the ice layer 8 (the interface between the ice layer 8 and the air 7). The microcontroller 3 stores the serial numbers of the piezoresistive sensors of the channel (each channel of sensing units has a unique serial number, the serial numbers are sequentially increased from top to bottom), and the serial numbers are set asa. When the voltage value of a certain path is smaller than that of the previous path, the piezoresistive sensor 1 of the path is considered to be in the ice water 9. Here also considered as the lower boundary of the ice layer 8 (the boundary between the ice layer 8 and the water under ice 9). The microcontroller 3 stores the serial number of the piezoresistive sensor in this channel, and sets it asb. Finally, the microcontroller 3 can calculate the thickness of the ice layer by the positions of the upper and lower interfaces of the ice layer 8, as shown in equation 2.
Claims (2)
1. The ice layer thickness measuring device based on the piezoresistive sensor is characterized by comprising the piezoresistive sensor (1), a chip selection circuit (2), a microcontroller (3), a resistance conversion circuit (4), a power circuit (5) and a shell (6);
a plurality of independent piezoresistive sensors (1) are fixed on the outer surface of the shell (6) at equal intervals; the chip selection circuit (2), the microcontroller (3), the resistance conversion circuit (4) and the power circuit (5) are all positioned in the shell (6); the chip selection circuit (2) comprises a plurality of chip selection switches (10), and the chip selection switches (10) are connected through a data bus; each piezoresistive sensor (1) is provided with two pins, and the number of the chip selection switches (10) is consistent with the total number of the pins of all the piezoresistive sensors (1); each pin of the piezoresistive sensor (1) is connected with the input end of one chip selection switch (10); the output ends of all chip selection switches (10) connected with the first pin of the piezoresistive sensor (1) are connected together to form a common end; the output ends of all chip selection switches (10) connected with the second pin of the piezoresistive sensor (1) are connected together to form another common end; the two public ends are respectively connected with the two input ends of the resistance conversion circuit (4); the output end of the resistance conversion circuit (4) is connected with a pin with an analog-digital conversion function on the microcontroller (3); the microcontroller (3) is connected with the chip selection circuit (2) through a data bus; the power supply circuit (5) respectively supplies power to the chip selection circuit (2), the microcontroller (3) and the resistance conversion circuit (4); the piezoresistive sensor (1) adopts FSR＠The front surface of the sensor is a sensitive layer of external force and needs to be in contact with the outside, and the back surface of the sensor is a sticking layer and is stuck on the outer surface of the shell (6) through an adhesive.
2. A piezoresistive sensor-based ice thickness measuring device according to claim 1, characterised in that said casing (6) is made of a low temperature resistant plastic material; the chip selection circuit (2), the microcontroller (3), the resistance conversion circuit (4) and the power circuit (5) are sealed in the shell (6) and are subjected to waterproof treatment; the piezoresistive sensor (1) is positioned outside the shell (6) and is subjected to anti-corrosion treatment.
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| CN201711403374.8A CN108195282B (en) | 2017-12-22 | 2017-12-22 | Ice layer thickness measuring device based on piezoresistive sensor |
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| CN1737490A (en) * | 2005-09-01 | 2006-02-22 | 太原理工大学 | Condenser type ice layer thickness sensor and detecting method thereof |
| CN202947782U (en) * | 2012-12-02 | 2013-05-22 | 淮北重科矿山机器有限公司 | Device detecting clear water layer interface online |
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| US4287472A (en) * | 1980-03-03 | 1981-09-01 | Exxon Production Research Company | Method for measuring the thickness of an ice sheet |
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