CN2166462Y - Multi-function digital coulometer - Google Patents

Abstract

The utility model relates to a multifunctional digital coulometer composed of a monolithic computer expanding system, an 8155 programmable interface chip, an analogue-digital conversion circuit and a detection loop. A monolithic computer is used for controlling to carry out the detection of electric quantity. The electric quantity can be immediately displayed by digitals, and the electric quantity and time can be preset and measured. A current detection range is from 2 microamperes to 2 amperes, the detection range of the electric quantity is from 5x10 (-8) to 9.9999x10 (5) coulombs, the resolution of the measurement of the electric quantity is 5x10 (-8) coulomb, and a basic error is smaller than 1%. The utility model can be widely applied to all industries of electrochemical analysis, organic electrochemical metering, electroplating industry, etc.

Description

Multi-function digital coulometer

The utility model relates to the computer control application.

Coulomb surveying instrument has following several to the measurement of electric weight haply at present: 1, utilize silver-colored deposition method, being about to the silver salt electrolytic tank seals in the tested loop, calculate electric weight according to the silver amount of separating out in whole conduction time, this method had been not only time-consuming, but also take material, can not adapt to the development of modern science and technology needs; 2, constant current chronometry is measured electric weight, and it is constant to limit loop current during this apparatus measures, according to calculating electric weight conduction time, so usable range is subjected to bigger restriction; 3, it is variable to measure loop current, but allows the range of current passed through little, and does not have electric weight, time preset function.When big electric current uses, maybe need preset when electric weight uses and just feel inconvenient.

Compare by the analysis to above-mentioned three kinds of electrical measuring instruments, the purpose of this utility model provides a kind of novel big multi-functional electrical measurement and control instrument of range ability.

The purpose of this utility model is achieved in that with 8031 single-chip microcomputers be core design electric weight TT﹠C system, measurement range is big, can the instant playback electric weight and electric weight, time can preset.This instrument all adopts big, medium scale integration (MSI), as the current-voltage conversion element, is electric current in the electric weight computing integration of voltage to the time to the Integral Transformation of time with precision resistance.

Owing to adopt such scheme detection electric weight and time preset very convenient, and the electrical measurement scope is big.This technical device index is as follows: detect 5 grades of current ranges: 2 peaces, 200 milliamperes, 20 milliamperes, 2 milliamperes, 200 microamperes; Electrical measurement scope 5 * 10 ^-8～9.9999 * 10 ⁵Coulomb; Electrical measurement resolution 5 * 10 ^-8Coulomb, electrical measurement fundamental error≤1%.

Below in conjunction with accompanying drawing the utility model is described in further detail.

Accompanying drawing 1 is the outside drawing of this coulombmeter, and instrument is long 28 centimetres, high 12 centimetres, wide 23 centimetres reference instrument case.On its front panel, 1 is 8 LED charactrons, and wherein 6 on the left side is a magnitude portion, and 2 on the right is an exponential part; 2 is 5 range interlocking keyswitches, from left to right is respectively 200 microamperes, 2 milliamperes, 20 milliamperes, 200 milliamperes, 2 peaces; 3～11st, by 6 function keys, 2 preset keys and 1 key groups that reset key is formed, wherein 3 for showing (and preset time) key conduction time, 4 is the electric current display key, 5 is electric weight algebraic sum (and preset key) display key, and 6 are positive electric weight (and presetting) display key; 7 for negative electricity (and presetting) display key, and 8 measure the electric weight key for " beginning/stop ", and 9 change several keys for presetting, and 10 are the presetting bit shift key, and 11 is reset key, and 12,13 is electric current input, output wiring terminal, and 14 is power switch.

When 14 were in the ON position, instrument powered up operation, and promptly display reminding symbol " READY " is ready (no matter later at which kind of state, as long as the reset key of pressing all can be got back to " READY " armed state).After pressing 8, promptly carry out the electrical measurement function, when electrical measurement, can at random press 3～No. 7 keys as required, for example, can observe the positive electric weight that instrument passed through at any one time by No. 6 keys with the corresponding physical quantity of instant playback.As pressing No. 8 key when the electrical measurement once more, then the pilot relay in the instrument disconnects, and finishes electrical measurement.After electrical measurement stopped, each relevant physical quantity still is held did not lose, and can observe by the corresponding function key again.(for example align that electric weight presets if before electrical measurement, preset in advance as long as by No. 6 keys 2 times, can see that a certain position in 8 LED charactrons is glittering, can increase 1 to glittering numeral by No. 9 keys this moment, if by No. 10 keys, can be 1 of glittering gt, other every data change method is identical), this moment is when carrying out electrical measurement by No. 8 keys again, when arbitrary measuring amount reaches prevalue, the pilot relay automatic cutout finishes to measure.

Accompanying drawing 2 is detailed electrical schematic diagrams.Among the figure 8031,74S373, the 27128th, have the MCS-51 single-chip microcomputer ultimate system of 16K program storage, crystal oscillator frequency is 6MHZ.The 8155(U4 that expands) interface chip, the internal RAM of its 256 byte is stored the measured value in each prevalue and arbitrary moment as 8031 external data memory.8155 A mouth, B mouth are responsible for 8 LED charactrons and are dynamically shown.Which shelves the C mouth is in according to the state-detection magnitude of current of K12～K52; Other 8155 A mouth and 8031 P3.0, P3.1 constitute dynamic scan keyboard matrix (totally nine keys) together.R ₁～R ₅(be respectively 2A～200 μ A according to current range, corresponding precision resistance is respectively 0.1 Ω-1000 Ω, and temperature-coefficient of electrical resistance is less than 0.4 * 10 for the accurate sampling resistor of different ranges ^-4Ω/℃, the relative nominal value deviation of resistance actual value is less than 0.5%), detected electric current converts voltage to by precision resistance.Fig. 2 precision resistance up and down+,-to be strings detect the electric current input and output side (being 12 among Fig. 1,13) in loop at electric weight at two ends.U5 is MC14433, and 3 half A/D converters (analog to digital conversion once needs 0.2 second approximately) will be by precision resistance R ₁～R ₅Adopt voltage signal convert digital quantity to and give 8031 P1 mouth, U6 is the MC1403 precision voltage source, and the reference voltage of 0.2V is provided to MC14433.K10～K50 in addition, K11～K51, three groups of switches of K12～K52 link.For example when the range switch was got to " 200 μ A " shelves, K10, the K11, the K12 that are actually in these three groups of switches connected, and sensed current flows through R by K11 so on the one hand ₅(1000 Ω), on the other hand K10 connect make MC14433 adopt voltage be R ₅On voltage.And simultaneously K12 connects, and program can be by reading U4(8155) there is the C mouth to know that current range is at that grade.Triode BG(9014) and relay J form to detect the on-off controller in loop, it is that low level, KJ disconnect that a boot program is set P3.5.When the user pressed No. 8 keys (beginning/stop) under this coulombmeter shows " READY " state after, program made P3.5 be changed to high level, the BG conducting, and the J adhesive, the KJ closure is normally measured.When the user pressed No. 8 keys (beginning/stop) or arbitrary measuring amount for the second time and reaches prevalue, EOP (end of program) was measured, and makes P3.5 put low level, and BG ends, and KJ disconnects.The measurement of electric weight is that basis gets by the integration that adds up of the electric current on the precision resistance to the time, and principle is as follows: 8031 on-chip timer T.Constitute 16 bit timing devices, the full 100mS of every meter produces once and interrupts, in the timer interrupt service subroutine, be provided with a software counter again, when regularly interrupt promptly having carried out No. 5 timer interrupt service subroutines through 5 times after, this software counter count value is 5(totally 0.5 second), this moment is just by interrupt INT O over the program, also promptly just allow this moment response MC14433 when certain analog to digital conversion finishes by its EOC pin to 8031 3.2 pin (INTO pin) proposition external interrupt application.Externally at first turning off INTO by software in the interrupt INT O service subprogram interrupts, so just can be so that the 8031 interruption applications that no longer respond the MC14433 proposition (are counted full numerical value 5 again unless wait until the software counter in the timer interrupt service subroutine, also promptly after 0.5 second, reopen INTO again and interrupt).So just can guarantee 0.5 second collection one secondary data.8031 from P1 mouth reading of data then, this is reflected after the data of size of current are multiplied by 0.5 second add up, promptly gets current charge value.And then each variable of difference and prevalue is poor, when variable equates with prevalue or presses No. 8 keys (beginning/stop) for the second time, finishes to measure.Because above function all is to finish in interrupt service subroutine, so the current state that shows certain physical quantity that is in is not influenced.

The fundamental purpose of this device is electrical measurement, as for preset, regularly, the demonstration of control and data can realize by different software.This program is organized in 27128 by assembly language, is omitted herein.Accompanying drawing 3 is the power pack of instrument, and system's power supply is positive and negative 5 volts of two parts, and alternating current is behind bridge rectifier, and 7805 provide 5 volts of voltages, and 7905 provide negative 5 volts of voltages.

This instrument can have following several using method:

One, directly measures electric weight.Show " READY " prompt after the instrument energized,, then begin to measure,, stop to measure by " beginning/stop " key again according to concrete response situation by " beginning/stop " key.

Two, electric weight observing and controlling.Calculate earlier and estimate required electric weight in the electrochemical reaction, preset in advance, begin to measure that when measured value reached prevalue, instrument cut off automatically and detects the loop, stopped to measure by " beginning/stop " key.

Three, time observing and controlling.Calculate the electrochemical reaction required time earlier, preset in advance, begin to measure that when Measuring Time arrived predetermined value, instrument cut off automatically and detects the loop, stopped to measure by " beginning/stop " key.

Claims (1)

1, a kind of digital coulombmeter of forming by 8031 extend system scps, 8155 programmable interface chips, analog to digital conversion circuit, detection loop, LED charactron and power pack, it is characterized in that by MC14433 and resistance error less than 0.5%, temperature coefficient is less than 0.4 * 10 ^-4Ω/℃ precision resistance R ₁～R ₅Form analog to digital conversion circuit, provide reference voltage to MC14433 with the MC1403 precision voltage source.

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