CN206609920U

CN206609920U - A kind of SCM Based multrirange capacitance measuring instrument

Info

Publication number: CN206609920U
Application number: CN201720127812.1U
Authority: CN
Inventors: 张惠国; 顾涵
Original assignee: Changshu Institute of Technology
Current assignee: Changshu Institute of Technology
Priority date: 2017-02-13
Filing date: 2017-02-13
Publication date: 2017-11-03
Anticipated expiration: 2027-02-13

Abstract

The utility model discloses a kind of SCM Based multrirange capacitance measuring instrument, including single-chip microcomputer operating circuit and the connected capacitance measurement circuit of difference, display circuit and key circuit, the capacitance measurement circuit uses the LC pierce circuits that LM393 chips are constituted, by the frequency of single chip computer measurement LC oscillation circuits, according to known capacitance, pass through the calculation function of single-chip microcomputer, calculate capacitance, finally, then by common I/O mouthfuls of single-chip microcomputer control liquid crystal displays the result of calculation of capacitance is shown.The measurement range of system is the μ F of 1pF ~ 12000, with multiple ranges, it can be needed to be selected by user according to user, with interacting for user realized by button, the realization of different ranges is to select different R values from disconnection by the closure of switch, so as to realize different ranges, system has certain practical value.

Description

A kind of SCM Based multrirange capacitance measuring instrument

Technical field

The utility model is related to capacitance measuring technique, more particularly to a kind of SCM Based multrirange capacitance measuring instrument.

Background technology

Current Electronic Testing field, it is quite varied that the measurement of electric capacity has been applied in e measurement technology and research and development of products. Electric capacity generally occurs with forms of sensor, therefore, and the development of capacitance measuring technique is exactly the development of capacitance sensor after all. Use exchange unbalanced bridge just can measure basic capacitance sensor by initial.Initial capacitance sensor has changed area, Become dielectric permittivity type and become type between pole plate.Present capacitance type sensor does more advanced and more advanced, having more than comparison now Capacitance-grid type capacitance sensor, ceramic capacitive pressure sensors etc..Capacitance measuring technique development also present capacitance measurement skill quickly Art also develops into diversification by unification.The manufacturer for making sensor both at home and abroad now also compares many, worldwide does electric capacity The relatively good company that sensor is done has：Japanese figaro, Germany tecsis, U.S. alphasense.China domestic measuring instrument The main bottleneck of device equipment development.Although native country test measurement industry is developed rapidly, China's exploitation to be objective is surveyed Try measuring instrument also universal relatively backward.Whenever lifting the reason for Chinese tester falls behind, many different sayings are just had, Such as precision is not high, and outward appearance is bad, poor reliability etc..In fact, these are all or superficial phenomenon, the real Chinese measuring instrument of influence Device development bottleneck be：

1. the status tested in whole goods batch is relatively low.Due to the influence of the traditional concept of people, in the system of product Make in flow, research and development are in core position all the time, and test and be then in subordinate and aided location.On this point, in almost institute Its one spot can be peeped in some department of research institution configurations.The reason in this cacodoxy, entire society is caused to test Attention degree not enough, so as to cause the serious scarcity of the talent in terms of tester, causes the basic scientific research of correlation weaker, This is a main bottleneck of Chinese measuring instrument development.In fact, even R＆D force in itself, to the attention degree of test with And it is also substantially inadequate to the research of instrument in itself.

2. application-oriented and modern marketing pattern is not set up really also.Native country instrument and equipment manufacturer is weight Research and development, pay attention to production, pay attention to the market of narrow sense, and the Modern Marketing system of complete set is not set up also and application oriented is ground Hair pattern.Traditional marketing model played great role in the planned economy age, but can not meet current global solution scheme The demand in popular age.So, for the gap between rapid drop and external advanced company, domestic instrument R ＆ D Enterprises should add Speed is realized from the transition towards imitated research and development to application oriented research and development.In particular with the quick increasing of domestic application demand It is long, provide fundamental driving force for this transition, it should utilize these power, track the fast development of application technology.

3. lack the material matching system of standard component.Due to history, the enterprise of the Chinese supporting industry of instrument is generally Very different small business, the research of standardization is also not kept pace with the fast development of demand, so as to cause the material of instrument to be matched somebody with somebody The technical merit for covering industry is relatively low.Although existing larger change at present, the requirement apart from whole industry also has certain distance, So, also standardization and modular research should be put into important position.Further, the condition being not reaching in technical merit Under, precision is pursued simply or high target is pursued, without handling the relation between stability well.Above-mentioned these are all restrictions The factor of native country Instrument Development.

The reliability and stability problem of China's measuring instrument has obtained very many attention in recent years, and situation has very It is big to take on a new look.Tester industry has passed over the ebb period at present, has come back to the track of fast development, especially several recently Year, in terms of China domestic instrument achieves significant progress, the particularly research and development of universal electric measuring apparatus, with external advanced product Gap just in rapid drop, the monopolization to external electronic instrument giant causes certain impact.With modularization and virtually The development of technology, is that the surveying instrument industry of China brings new opportunity, adds governments at all levels' pay attention to day by day, Yi Jizhong State independently applies the rapid progress of research on standard, is all providing unprecedented power and opportunity for the industry.From China Electronics As can be seen that the surveying instrument of China is every year all with the speed more than more than 30% quick in information industry statistical yearbook Increase.During this rapid growth, undoubtedly expedited the emergence of out it is many test industry emerging organizations, also expedited the emergence of out it is many batches of can By the higher product of property and stability.

In view of above-mentioned prior art, the applicant has made beneficial design, technical scheme described below be Produced under this background.

Utility model content

The utility model purpose is：A kind of SCM Based multrirange capacitance measuring instrument is provided, with simple in construction, inspection The advantages of comprehensive, with low cost, stability is preferable is surveyed, with good application value.

The technical solution of the utility model is：

A kind of SCM Based multrirange capacitance measuring instrument, including single-chip microcomputer operating circuit and the connected electricity of difference Capacitance measuring circuits, display circuit and key circuit, the LC oscillators electricity that the capacitance measurement circuit is constituted using LM393 chips Road.

It is preferred that, described single-chip microcomputer operating circuit uses STC89C52 single-chip microcomputers.

It is preferred that, the capacitance measurement circuit includes capacitor charge and discharge circuit and constitutes LC vibrations using LM393 chips U1A Device；Described capacitor charge and discharge circuit is made up of LM393 chip comparators U1B, passes through the charging interval measured and charging resistor Calculate capacitance size.

It is preferred that, the key circuit uses nonencoded keyboard.

It is preferred that, the display circuit uses LCD1602 LCDs, for showing capacitance and some are corresponding Metrical information.

It is preferred that, the key circuit includes monolithic processor resetting button Btn1, calibration knob Btn2, function switching push button Btn3, the Btn3 are used to switch between measurement small capacitances and measurement electrochemical capacitor.The utility model has the advantages that：

SCM Based multrirange capacitance measuring instrument provided by the utility model, can according to known capacitance, By the calculation function of single-chip microcomputer, capacitance is calculated, finally, then common I/O mouthfuls of control liquid crystal screen displays for passing through single-chip microcomputer The result of calculation of capacitance is shown.Have the advantages that simple in construction, comprehensive, the with low cost, stability of detection is preferable, with good Good application value.

Brief description of the drawings

Below in conjunction with the accompanying drawings and embodiment is further described to the utility model：

Fig. 1 is the system block diagram of SCM Based multrirange capacitance measuring instrument described in the utility model；

Fig. 2 is the function relation figure between capacitor charging time described in the utility model and electric capacity both end voltage；

Fig. 3 is capacitance measurement circuit electrical schematic diagram described in the utility model；

Fig. 4 is the electrical schematic diagram of capacitor charge and discharge circuit described in the utility model；

Fig. 5 is singlechip minimum system circuit figure described in the utility model；

Fig. 6 is the electrical schematic diagram of key circuit described in the utility model；

Fig. 7 is the electrical schematic diagram of display circuit described in the utility model；

Fig. 8 is the circuit diagram of LCD1602 display circuits of the present utility model.

Embodiment

As shown in figure 1, a kind of system frame of SCM Based multrirange capacitance measuring instrument disclosed in the utility model Figure, including including single-chip microcomputer operating circuit and the connected capacitance measurement circuit of difference, display circuit and key circuit, it is described Capacitance measurement circuit uses the LC pierce circuits that LM393 chips are constituted.

This capacitance measurement method of the utility model mainly measures electric capacity by one piece of LM393 chip, and circuit is one The individual LC oscillators being made up of LM393.System is mainly made up of four major parts, the design of single-chip microcomputer operating circuit, LM393 cores Piece circuit design, key circuit design, display circuit design.By the frequency F of single chip computer measurement LC oscillation circuits₁, then basis Standard capacitance C₁, obtain electric capacity C_X,Wherein, F1 is intrinsic frequency, and F2 is accessed after testing capacitor Frequency.As long as we can measure the frequency of LC pierce circuits, it is possible to calculate the electric capacity of measurement.Calculate frequency Method can utilize the counter T of single-chip microcomputer₁And interruptionWith the use of measuring, suitable simple of this research method.

As shown in Fig. 2 being the function relation figure between capacitor charging time and electric capacity both end voltage, it is illustrated that curve can be obtained To the universal law of charging process：U_CExponentially rise, U_CStart change very fast, slow down gradually later, and slowly Its end value of convergence, as t=τ, U_C=0.632E (E is supply voltage)；This measuring instrument is exactly to utilize single chip computer measurement U_C=0 To 0.632E this periods, measured capacitance values are calculated with following formula：Circuit by comparator U1B, discharge transistor Q1, Q2 etc. is constituted.Comparator positive input terminal is set as U_C, (U_C=0.632E, regulation Rref is obtained), reverse input end connects measured capacitance C_X, when single-chip microcomputer P15 pins are low level, electric capacity electric discharge.Note the sourcing current very little of 51 single-chip microcomputer pins, it is impossible to directly drive Dynamic Q1, otherwise discharge time can be very long.When single-chip microcomputer P15 pins are high level, electric capacity charging, when being charged to U_CWhen, compare Device is overturn, triggering single-chip microcomputer external interrupt 0, can calculate electric capacity by the charging interval measured and the size of charging resistor big It is small.

As shown in figure 3, capacitance measurement circuit, the LC oscillators that LM393 chips (U1A) are constituted.Shaken by single chip computer measurement LC Swing the frequency F in loop₁, then according to standard capacitance C₁, obtain electric capacity C_X,Fig. 4 is LM393 cores The capacitor charge and discharge circuit of the compositions such as piece comparator U1B, discharge transistor Q1, Q2, passes through the charging interval measured and charging electricity The size of resistance can calculate capacitance size.

As shown in figure 5, singlechip minimum system circuit figure, core is single chip circuit, it is contemplated that need an interruption defeated Enter, the need for memory capacity, external interface are to one-chip machine port and take into account cost-effective principle, selected conventional STC89C52 single-chip microcomputers.STC89C52 is a kind of low-power consumption, the 8-digit microcontroller of high-performance CMOS 8, with 8K in-system programmable components Flash storage.On a single chip, 8 bit CPUs and in-system programmable components Flash of dexterity are possessed so that STC89C52 is numerous Embedded Control application system provides the high flexible, solution of super efficient.With following standard feature：8k bytes Flash, 512 byte RAM, 32 I/O mouth lines, WatchDog Timer, built-in 4KB EEPROM, MAX810 reset circuits, three 16 are fixed When device/counter, one 6 vectorial 2 grades of interrupt structures, full duplex serial port.Other STC89X52 can be down to 0Hz static logics behaviour Make, support 2 kinds of softwares that energy-saving mode may be selected.Under idle pulley, CPU is stopped, it is allowed to RAM, timer/counter, string Mouth, interruption work on.Under power down protection mode, RAM contents are saved, and oscillator is frozen, and all work of single-chip microcomputer stop, Untill next interruption or hardware reset.Highest operation frequency 35MHz, 6T/12T is optional.It is most simple that STC89C52 works Single circuit is that its periphery connects a crystal oscillator and a reset circuit, is connected with the mains to single-chip microcomputer and ground, single-chip microcomputer just can be with work Make.As shown in Figure 5, what 9 pin were external is key reset circuit, 18,19 pin it is external be crystal oscillating circuit, so, just constitute The necessary circuits of single-chip microcomputer normal work.Meanwhile, to make P0 mouthfuls of normal works, and increase its carrying load ability, P0 mouthfuls need to connect Pull-up resistor (is not drawn into) in figure.

As shown in fig. 6, key circuit circuit diagram, button be realize it is interactive compare intuitively interface, can pass through Button realizes that people want the different work for allowing single-chip microcomputer to do.Keyboard is the set of one group of button, and key is a kind of open type switch, Usually two contacts of button are off, and are that they are closed by lower key.Keyboard Coded keyboard and nonencoded keyboard, case The identification of part can produce the referred to as encoded keyboard of key numbering or key assignments by special hardware realization of decoding, and lack this key Disk coding circuit will lean on the referred to as nonencoded keyboard that self-programmed software is recognized.Singlechip group into circuit system and Artificial Intelligence Instrument In, it is more nonencoded keyboard.Fig. 6 is exactly a kind of than more typical key circuit, when button is not pressed, Output is high level, when button is pressed down, the low level of output.Wherein Btn1 is monolithic processor resetting button；Btn2 It is calibration knob, clearing display can be pressed at any time when measuring small capacitances；Btn3 is function switching push button, in measurement Switch between LCF (frequency, small capacitances, inductance) and measurement electrochemical capacitor.

As shown in fig. 7, display circuit circuit diagram, LCD is abundant, ultra-thin light and handy with its micro energy lose, small volume, display content Plurality of advantages, is increasingly widely applied in pocket meter and low-power consumption application system.Character type presented here Liquid Crystal Module is a kind of liquid crystal display that character is shown with 5x7 dot patterns, can be divided into 1 row 16 according to the capacity of display Individual word, 2 row, 16 words, 2 row, 20 words etc., we use 1602 Liquid Crystal Modules of 2 row, 16 words here.Fig. 7 is exactly Common LCD1602 LCDs pinouts.1st pin：VSS is ground power supply.2nd pin：VDD connects 5V positive supplies.3rd pin：V0 For liquid crystal display setting contrast end, contrast is most weak when connecing positive supply, and contrast highest during earthing power supply, contrast is too high When can produce " ghost ", contrast can be adjusted by 10K potentiometer when using.4th pin：RS selects for register, Selection instruction register when selection data register, low level during high level.5th pin：RW is reading writing signal line, is entered during high level Row read operation, carries out write operation during low level.With write instruction or address can be shown when RS and RW are jointly low level, when RS is that low level RW can read busy signal when being high level, when RS is that high level RW can write data when being low level.6th Pin：E ends be Enable Pin, when E ends by high level saltus step into low level when, Liquid Crystal Module performs order.7th~14 pin：D0~D7 For 8 bidirectional data lines.15th~16 pin：Empty pin.

As shown in figure 8, LCD1602 connect with P0 mouthfuls, for showing capacitance and some corresponding metrical informations.

Above-described embodiment is only to illustrate technical concepts and features of the present utility model, and its object is to allow be familiar with technique People can understand content of the present utility model and implement according to this, protection domain of the present utility model can not be limited with this.It is all The modification done according to the Spirit Essence of the utility model main technical schemes, should all cover in protection domain of the present utility model Within.

Claims

1. a kind of SCM Based multrirange capacitance measuring instrument, it is characterised in that：Including single-chip microcomputer operating circuit and respectively with Its capacitance measurement circuit, display circuit and key circuit for connecting, the capacitance measurement circuit uses the LC that LM393 chips are constituted Pierce circuit.

2. SCM Based multrirange capacitance measuring instrument according to claim 1, it is characterised in that：Described single-chip microcomputer Operating circuit uses STC89C52 single-chip microcomputers.

3. SCM Based multrirange capacitance measuring instrument according to claim 2, it is characterised in that：The capacitance measurement Circuit includes capacitor charge and discharge circuit and constitutes LC oscillators using LM393 chips U1A；Described capacitor charge and discharge circuit by LM393 chip comparators U1B is constituted, and capacitance size is calculated by the charging interval and charging resistor that measure.

4. SCM Based multrirange capacitance measuring instrument according to claim 2, it is characterised in that：The key circuit Using nonencoded keyboard.

5. SCM Based multrirange capacitance measuring instrument according to claim 2, it is characterised in that：The display circuit Using LCD1602 LCDs, for showing capacitance and some corresponding metrical informations.

6. SCM Based multrirange capacitance measuring instrument according to claim 4, it is characterised in that：The key circuit Including monolithic processor resetting button Btn1, calibration knob Btn2, function switching push button Btn3, the Btn3 are in measurement small capacitances Switch between measurement electrochemical capacitor.