CN203849127U - Rapid density measuring instrument - Google Patents

Abstract

The utility model relates to a rapid density measuring instrument, which comprises a main body of the density measuring instrument, a measuring cup, a measuring frame, a liquid and a measuring ball. , the main body of the measuring instrument is equipped with a pressure sensor and a microprocessor, data acquisition, A/D conversion and liquid crystal display circuit; the main body of the measuring instrument is placed on the base of the measuring frame, and there is a light thin line on the hook, and one end is tied to the measuring object Or measure the ball, adjust the lifting bracket to place the measuring object or the measuring ball outside the measuring cup, or immerse it in the liquid in the measuring cup placed on the measuring plate, without contact with the measuring cup, the measuring instrument is combined The pressure sensor and high-performance microprocessor can realize the function of fast measurement and display of solid and liquid density, and can store various measurement information at the same time. It is suitable for experimental measurement and practical application of physics courses in schools at all levels.

Description

A fast density measuring instrument

technical field

The utility model relates to a fast density measuring instrument, which belongs to the fields of electronic technology application and experimental application.

Background technique

Experiments are very important in the teaching of science and engineering students. While training students to operate independently, they can intuitively combine theory with practice, allowing students to understand the theory more deeply. The measurement of object density is a very basic experiment in physical experiments. At present, the measurement of object density generally adopts the mass volume method, that is, first use a balance to measure the mass of the object, then use a graduated cylinder to measure the volume, and then calculate according to the density formula. This method requires two steps of operation, and cannot perform fast measurement and real-time display.

Density is widely used in daily production and life. It can identify the materials that make up an object, calculate the composition of various substances contained in an object, calculate the volume of an object with a relatively complex shape, determine whether an object is solid or hollow, and calculate Density is also an important basis for identifying unknown substances, such as internal pressure and buoyancy of liquids. Therefore, density measurement, especially fast and high-precision density measurement, is a need in today's experiments and life processes.

The utility model adopts a high-performance microprocessor, through the force-electric conversion of the pressure sensor and the calculation of the microprocessor, combined with the display of the liquid crystal screen, the experimental measurement of the object density can be carried out quickly and intuitively, and it can also be used in daily life in the application.

Utility model content

Aiming at the deficiencies of existing measuring and experimental instruments, the utility model improves the traditional density measuring method. The utility model combines a high-performance microprocessor and a pressure sensor, and simply measures the pressure and pressure of the object together with the measuring cup. Then the total pressure when the object is suspended with light weight thin wire and submerged in the liquid can be calculated by the microprocessor to quickly measure the density of solid or liquid. The measuring instrument accurately converts the pressure signal into an electrical signal through a bridge circuit, and calculates the data parameters by the microprocessor, and finally outputs the density measurement result on the LCD screen.

The utility model includes a density measuring instrument host, a measuring cup, a measuring frame, liquid and measuring balls. The density measuring instrument host is provided with a measuring disk, a liquid crystal screen, function and digital input buttons, and a measurement button. There are pressure sensors and microprocessors, data acquisition, A/D conversion and liquid crystal display circuits; the main body of the measuring instrument is placed on the base of the measuring stand, and there is a light thin line on the hook, one end is tied to the measuring object or measuring ball, and the adjustment The lifting bracket can place the measuring object or the measuring ball outside the measuring cup, or immerse it in the liquid suspended in the measuring cup placed on the measuring plate, without contacting the measuring cup, by measuring the measurement of the object and the liquid inside The total pressure of the cup and the pressure when the object is suspended and immersed in the liquid can be used to obtain the density of the measured object. The pressure sensor is arranged at the bottom of the measuring plate, and the pressure electrical signal is obtained through a digital acquisition circuit and converted by A/D. , transmitted to the microprocessor, and the processed measurement data is displayed on the LCD screen.

The microprocessor in the main unit of the measuring instrument adopts a high-performance 16-bit microprocessor MSP430F2012 newly launched by TI. It has a built-in operating frequency of up to 16MIPS, ultra-low power consumption, and usually works in a sleep state to save power. When an interrupt occurs, it can wake up from an ultra-low power consumption 500nA standby mode to a full-speed working mode in less than 1μs. In terms of peripheral functional devices, MSP430F2012 also integrates 10-bit AD, 16-bit timer, capture comparator, watchdog timer, power-down detection, USI communication module, etc. MSP430F2012 can meet the needs of low power consumption and high performance.

The data acquisition circuit of the utility model adopts four resistance strain type pressure sensors. The resistance strain type pressure sensor is mainly composed of an elastic body and a resistance strain gauge. The circuit adopts a Wheatstone bridge. When the elastic body is deformed under load, the resistance conversion element is deformed by stretching or compressing the strain gauge, and its resistance value will be Changes will cause the bridge to lose balance, generate corresponding differential signals, and obtain the required physical quantities after amplification and analog-to-digital conversion circuits. The resistance strain sensor has the characteristics of simple circuit, small size, compact structure, stable performance, high precision and sensitivity, and less strict requirements on the measurement environment.

The liquid crystal display circuit of the utility model adopts a 128×64 liquid crystal display screen with low voltage, low power consumption, a Chinese character library, and a ST7920 controller. It has multiple interface modes of 4/8-bit parallel, 2-wire or 3-wire serial, its display resolution is 128×64, built-in 8192 16×16-dot Chinese characters and 128 16×8-dot ASCII character sets. The interface of this module is flexible, and the operation instructions are simple and convenient. It can display Chinese characters in 8×4 rows and 16×16 dot matrix, and can also complete graphic display, which can form a full Chinese human-computer interaction graphic interface.

Description of drawings

Figure 1 is the appearance of the host of the density measuring instrument, in which 1 is the measuring panel, 2 is the LCD screen, 3 is the function and digital input buttons, and 4 is the measurement button.

Figure 2 is a schematic diagram of measurement, in which 5 is the base of the measuring frame, 6 is the bracket of the measuring frame, 7 is the lifting bracket, 8 is the hook, 9 is the light thin wire, 10 is the object to be measured or the measuring ball, and 11 is the measuring cup , 12 is a density measuring instrument host.

Figure 3 is a schematic diagram of the measuring instrument system circuit.

Figure 4 is a bridge circuit diagram of the measuring instrument

Detailed ways

In conjunction with the accompanying drawings, the circuit and working conditions of a rapid density measuring instrument will be described in detail below.

For the integrity of the measuring instrument and the convenience of detection and debugging, modularization is adopted in the production of the circuit, and the power supply module, data processing module, display module and sensor module are set separately, and then multiple modules are placed on the same circuit board at the same time.

In the main body of the density measuring instrument, four pieces of resistance strain pressure sensors with identical performance are used to form a Wheatstone bridge circuit. The microprocessor receives the voltage signal and displays it as the density of the measured object after calculation and conversion. In the bridge circuit, the change of the bridge output voltage is proportional to the algebraic sum of the resistance change rate of each arm. Vout is the output voltage of the sensor bridge circuit.

The input button module of the utility model adopts a 4*4 matrix keyboard. The matrix keys are easy to use and operate, and occupy less I/O ports, etc., which can meet the needs of hardware design. The number keys are used to input the density of the known liquid or measuring ball, and the N0, N1, N2 function keys in the input keys are used to quickly store the pressure of the object, the measuring cup and the liquid and the total pressure of the object after being buoyant in the In the memory, to facilitate the later calculation of the microprocessor.

The A/D conversion circuit of the utility model adopts a high-precision HX711 chip, and the HX711 is a 24-bit A/D converter chip specially designed for high-precision electronic scales. The regulated power supply provided in the chip can directly provide power to the external sensor and the A/D converter in the chip. There is no need for an external power supply on the system board. The automatic reset function of the clock oscillator in the chip simplifies the initialization process of starting up.

This measuring instrument can conveniently measure the density of solids and liquids. By adjusting the lifting bracket, the measuring object or measuring ball can be placed outside the measuring cup, or the measuring object or measuring ball can be immersed in the liquid suspended in the measuring cup. But not in contact with the measuring cup.

In the experiment, when measuring the solid density, the gravity of the measured object is set as: G=mg. In the actual experimental measurement, the measuring cup is generally filled with water, and the total gravity of the measuring cup and the water inside is: G ₀ =m ₀ g

Then the pressure when the measured object and the measuring cup containing the liquid are put together on the measuring plate is: N ₀ =mg+m ₀ g

As shown in the measurement schematic diagram, the object to be measured is suspended and immersed in the liquid in a light thin wire, then the object to be measured is affected by gravity and buoyancy, and the pressure on the measuring disc is: N ₁ =mg+m ₀ g-(mg-F _floating )＝m ₀ g+F _floating

In the experimental operation, when the measuring cup and the liquid are placed on the measuring plate, the measured value is set to 0, even if m ₀ g=0, then N ₀ and N ₁ are transformed into: N ₀ = mg; N ₁ = F _float = ρ _water gV, where V is the volume of liquid displaced by the measured object, that is, the volume of the object.

Combining the two formulas, measure the total pressure N ₀ of the object and the measuring cup containing the liquid and the pressure N ₁ when the object is suspended and immersed in the liquid, that is, the two measured values and the known density of water can be used to calculate the measured object Density, and displayed by the LCD screen:

Similarly, when measuring the density of a liquid, use a measuring ball with a known density, set the measured value of the measuring cup and the liquid on the measuring plate to 0, and place the measuring ball and the measuring cup together on the measuring plate. The pressure value is recorded as N ₀ , and the pressure value when the measuring ball is suspended and immersed in the measured liquid is recorded as N ₂ , then the density of the liquid is:

This measuring instrument combines a pressure sensor and a high-performance microprocessor to measure the density of solids and liquids. Compared with mechanical balances and other instruments, it is more convenient and faster, and it avoids errors caused by human factors and improves efficiency. measurement accuracy. At the same time, the measuring instrument can store various measurement information, which is suitable for experimental measurement and practical application of physics courses in schools at all levels.

Claims (3)

1. a fast density measuring instrument, it is containing penetron main frame, measuring cup, measurement bay, liquid and measurement bead, it is characterized in that: on penetron main frame, be provided with measurement dish (1), liquid crystal display (2), function and digital input key (3), measure button (4), in penetron main frame, be provided with pressure transducer and microprocessor, data acquisition, A/D conversion and liquid crystal display circuit; Its measuring instrument main frame is placed on measurement bay base (5), on hook (8), there is lightweight fine rule, one end hitches to be measured object or measures bead, regulate lifting support (7) to be positioned over outside measuring cup measuring object or measuring bead, or its submergence is hung in the liquid that is placed in the measuring cup on measurement dish, do not contact with measuring cup; Its pressure transducer is arranged on measurement dish bottom, and electric pressure signal obtains by digital acquisition circuit, and after A/D conversion, is transferred to microprocessor, and measurement data after treatment is shown by liquid crystal display.

2. a kind of fast density measuring instrument according to claim 1, is characterized in that: the microprocessor in its penetron main frame adopts the MSP430F2012 chip of TI company.

3. a kind of fast density measuring instrument according to claim 1, is characterized in that: the pressure transducer in its penetron main frame adopts the identical resistance strain type pressure sensor of four piece performances, and forms wheatstone bridge circuits.