http___www.informatika.buzdo.com_s938-ph-metar.htm_1.xml
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'Informatics in practice' may not mean very costly systems or devices. True, there are very expensive, but very affordable priced and not so great for overall dimensions. One example is the 'Seven Easy pH Meter' firm METTLER TOLEDO. pH meter is sensory devices for measuring the acidity of a solution that measures the concentration of hydrogen ions in them i.e. pH. Serves as an electrical sensor glass membrane which has a certain thickness, and in which when set between two electrolyte ion exchange on both sides of the membrane. In this case it comes to the appearance of the potential difference between two solutions separated by a glass dome which in turn depends on the concentration of hydrogen ions. If the concentration in solution is constant, then the potential difference depends on the concentration of hydrogen ions in the second solution. Favorable electrical meter amplifiers measure the potential of glass electrode is dependent on the concentration of H+ ions. Although the instruments called pH meters are not limited only to the determination of the concentration of H+ ions. Elements or compounds which are determined solely depend on potentiometric sensor that is on used indicator electrode. Manner of its use is shown in the following figure, a glass cup in which the electrode is best illustrated by its size. The instrument has a separate power adapter, and can operate on batteries. In the left corner of the image shows the ports used. There is a port for an external power supply, connection to the electrode and ATC connector when using electrodes with built-in or remote temperature 'probe', and the DB9 connector type to send data to the computer. Display of 'Liquid Crystal' technology, which now has almost every hour or cell phone, shows about 13 different data sets or incurred during the measurement. The most important of these are: Part of the technical specifications in the factory instructions shown again: ----------------------------------------------------------- Unit : pH mV °C Measurement Range : 0.00 - 14.00 ± 1999 (-5)-(+105) Resolution : 0.01 1 0.1 Relative Accuracy : ± 0.01 ± 1 ± 0.5 pH-calibration : 1, 2, or 3 points Isopotential Point : 7.00 pH Outputs: RS 232 serial Baud rate : 1200 Data bit : 8 Stop bit : 1 Parity : none pH Input : Combination electrode Impedance : > 1'000'000'000'000 Ω (ohm) Size/Weight : 180 × 180 × 65 mm / 0.61 kg Material Casing : ABS, PC enforced Electrode stand : ABS, PC enforced Membrane keypad : Polyester Power Requirements : 230V/50 Hz, 10 VA, 9 V DC ----------------------------------------------------------- The basic electrical characteristics of what should be noted is a small data rate and a very high input impedance of the terminal electrodes. The reason for this is the elimination of the impact of electronic devices on the course and results of the measurements, because of such a high input impedance input through the electronic circuit of the instrument does not pass almost no current. To make the computer accepted and deposited the instrument sends data to the parameters set by the previous speed serial RS 232 port, and a program that monitors aid. This could be some kind of very expensive software support that will be able to read, store data, analysis, graphics and the like and may be used and simplest TELNET program support which the parameters are set as shown below. If the computer and the instrument parameters are not agreed not to receive any view or will be unreadable. As there is no indication in the particular specifications, data exchange is done in ASCII code. The following figure shows how the user is allowed to take data from the instrument are saved to file MARIO.TRM. Figure 4.2.3 shows a group of 'Accessories', which was launched from the TERMINAL application and that before accepting the data must be set the parameters for the computer to communicate with the instrument. Data are presented in three columns. Show basic pH measured value. As the speed of data exchange only about a hundred characters per second, it is a slow track changes in the chemical process. What data obtained? Everything that he wants. They can be transferred to Excel on Windows XP/Vista/7 platforms, process and analyze or in some other professional program of profession. It may be noted that the data files are marked by the principle NAME.TYPE, which is specific for the DOS operating system. It should nevertheless be familiar with the basics of a computer. If you are using a DOS-Windows operating systems should always keep in mind the image specification is shown in Chapter 4.1.1. The difference compared to newer types of 'window' was later used as file names up to 32 characters, but kept for compatibility and shorter, so the example folder (directory) [C:\MY- MEASUREMENT\] in Windows XP or Windows 7 operating system, displayed as [C:\MY-MEA-1\] if the data is transferred to the Windows 3.11 operating system. Therefore, in such cases, make sure that the file names are understandable and no more than eight characters because of how quickly distinguished as [C:\MY-MEA-1\], [C:\MY-MEA-2\] or [C:\MY-MEA-3\]. Despite all the beauties offered by newer Microsoft operating systems not advisable to forget the 'good old DOS', at least some of its basic settings and commands that XP/Vista/7 and is used in the 'Command Prompt' window. SUMMARY: Take a look at the last two pictures, it is evident that these icons of Windows 3.11 OS. Thus, the operating system that can no longer be developing long nor products, but is normal in today's terms at a very modest computers. In this case, the type of computer is xx386 with 8 MB of RAM and disk capacity of about 100 MB. Nevertheless one stylish device uses very undemanding computing resources and can efficiently serve a purpose: measuring the pH of a solution. So, do not 'throw' old computers and OS as they can effectively serve despite obsolescence. Low cost and reliability of these devices make them ideal for environmental monitoring in order to face up to the time of climate change that we follow.
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'Informatika u praksi' ne mora podrazumijevati vrlo skupe sustave ili uređaje. Istina, ima ih vrlo skupih, ali i vrlo pristupačnih po cijene i ne tako velikih po gabaritima. Jedan od primjera je 'Seven Easy ph Metar' firme METTLER TOLEDO. pH-metar je osjetilna naprava za mjerenje kiselosti otopina s kojom se mjeri koncentracija vodikovih iona u njima tj. pH. Kao električno osjetilo služi staklena membrana koja ima određenu debljinu i na kojoj kada se postavi između dva elektrolita dolazi do zamjene iona na objema stranama membrane. U ovakvom slučaju dolazi do pojave razlike potencijala između dviju otopina odvojenih staklenom membranom a koja ovisi o koncentraciji vodikovih iona. Ako je koncentracija u jednoj otopini konstantna, onda razlika potencijala ovisi o koncentraciji vodikovih iona u drugoj otopini. Pogodnim elektrometarskim pojačalima mjeri se potencijal staklene elektrode koji je ovisan o koncentraciji H+ iona. Iako se ovi instrumenti zovu pH-metri oni nisu ograničeni samo na određivanje koncentracije H+ iona. Elementi ili spojevi koji se određuju ovise samo o potenciometrijskom senzoru tj. o upotrijebljenoj indikatorskoj elektrodi. Način njegove uporabe prikazan je na narednoj slici a čaša u kojoj je elektroda najbolje ilustrira njegovu veličinu. Instrument ima odvojen ispravljač za napajanje, a može raditi i na baterije. U lijevom uglu slike prikazani su priključci koje koristi. Tu je priključak za vanjsko napajanje, priključak za elektrodu i ATC priključak ako se koristi elektroda s ugrađenom ili odvojenom temperaturnom 'probom', i priključak tipa DB9 za slanje podataka prema računalu. Pokazivač 'Liquid crystal' tehnologije, kojeg danas ima gotovo svaki sat ili mobitel, pokazuje oko 13 različitih podataka postavljenih ili nastalih tijekom mjerenja. Najvažniji od njih su: Dio tehničkih specifikacija iz tvorničke upute prikazan je nadalje: ----------------------------------------------------------- Unit : pH mV °C Measurement Range : 0.00 - 14.00 ± 1999 (-5)-(+105) Resolution : 0.01 1 0.1 Relative Accuracy : ± 0.01 ± 1 ± 0.5 pH-calibration : 1, 2, or 3 points Isopotential Point : 7.00 pH Outputs: RS 232 serial Baud rate : 1200 Data bit : 8 Stop bit : 1 Parity : none pH Input : Combination electrode Impedance : > 1'000'000'000'000 Ω (ohma) Size/Weight : 180 × 180 × 65 mm / 0.61 kg Material Housing : ABS, PC enforced Electrode stand : ABS, PC enforced Membrane keypad : Polyester Power Requirements : 230V/50 Hz, 10 VA, 9 V DC ----------------------------------------------------------- Osnovno od električkih osobina što treba zapaziti je mala brzina prijenosa podataka te vrlo velika ulazna impedancija na priključku elektrode. Razlog tome je eliminacija utjecaja elektroničkog uređaja na sam tijek i rezultate mjerenja, jer zbog ovako velike ulazne impedancije kroz ulazni elektronički krug instrumenta ne prolazi gotovo nikakva struja. Da bi računalo prihvatilo i pohranilo podatke koje instrument šalje treba prema prethodnim parametrima podesiti brzini serijskog RS 232 port-a te aplikaciju koja ga nadzire. To može biti nekakva vrlo skupa aplikacija koja će imati mogućnost očitavanja, spremanja podataka, analize, grafičkog prikaza i sličnog a može poslužiti i najprostija TELNET aplikacija kojoj su parametri podešeni kako prikazuje naredna slika. Ako parametri računala i instrumenta nisu usuglašeni neće se dobiti nikakav prikaz ili će biti nečitak. Kako nema osobitih naznaka u specifikacijama, razmjena podatak vrši se u ASCII kodu. Naredna slika pokazuje kako je Mario omogućio da se podaci iz instrumenta spreme u datoteku MARIO.TRM. Slika 4.2.3 prikazuje grupu 'Accessories' iz koje je pokrenuta aplikacija TERMINAL i kojoj se prije prihvata podataka moraju podesiti parametri za komunikaciju računala s instrumentom. Podaci su prikazani u tri stupca. Prikazuju osnovne pH vrijednosti dobivene mjerenjem. Kako je brzina razmjene podataka svega oko stotinjak znakova u sekunda, radi se o praćenju sporih promjena u kemijskom procesu. Što s dobivenim podacima? Sve što se želi. Može ih se prebaciti u EXCEL na Windows XP/Vista/7 platformi i obrađivati i analizirati ili u neki drugi profesionalni program struke. Može se primijetiti da datoteka s podacima ima oznaku po načelu NAZIV.TIP, što su oznake DOS operativnih sustava. Treba ipak poznavati nešto iz osnova rada računala. Ako se koriste DOS-Windows operativni sustavi uvijek treba imati na umu sliku specifikacije datoteke prikazanu u poglavlju 4.1.1. Razlika u odnosu na novije vrste 'prozora' je što noviji koriste imena datoteka do 32 znaka, ali radi kompatibilnosti čuvaju se i kraća, pa će se recimo folder (direktorij) [C:\MOJI-PODACI\] u Windows XP ili Windows 7 operativnom sustavu, prikazati kao [C:\MOJI-P-1\] ako se podaci prebace u Windows 3.11 operativni sustav. Stoga u takvim slučajevima treba paziti da imena datoteka budu razumljiva i ne duža od osam znakova jer kako brzo razlikovati što je [C:\MOJI-P-1\], [C:\MOJI-P-2\] ili [C:\MOJI-P-3\]. Unatoč svim krasotama koje nude noviji Microsoft operativni sustavi nije uputno zaboraviti 'dobri stari DOS', barem neke njegove osnovne postavke i komande koje i XP/Vista/7 koristi u 'Command Prompt' prozoru. SAŽETAK: Ako se dobro pogledaju zadnje dvije slike može se zapaziti da su to ikone Windows 3.11 OS. Dakle, operativni sustav koji se odavno više ne razvija niti proizvodi, ali uredno radi za današnje pojmove na vrlo skromnim računalima. U ovom slučaju računalo je tipa xx386 s 8 MB radne memorije i diskom reda veličine 100 MB. Unatoč navedenom jedan moderan uređaj koristi vrlo nezahtjevne računalne resurse i može vrlo učinkovito poslužiti svrsi: mjerenju pH vrijednosti neke otopine. Dakle, ne 'bacati' stara računala i OS jer mogu unatoč zastarjelosti učinkovito poslužiti. Niska cijena i pouzdanost ovih uređaja čine ih idealnima za praćenje stanja u okolišu kako bi se na vrijeme suočili s klimatskim promjenama koje nam slijede.