Possible sources of error

Titration is a sensitive analytical method that lets you determine an unknown concentration of a chemical in solution by introducing a known concentration of another chemical. Several factors can cause errors in titration findings, including misreading volumes, mistaken concentration values or faulty technique. Care must be taken as the solution of the known concentration is introduced into a specific volume of the unknown through laboratory glassware such as a burette or pipette. Indicators are used to determine when a reaction has come to an end.

End Point Error

The end point of a titration is when the reaction between the two solutions has stopped. Indicators, which change color to indicate when the reaction has stopped, do not change instantly. In the case of acid-base titration, the indicator may first lighten in color before changing completely. Also, each individual perceives color slightly differently, which affects the outcome of the experiment. If the color has changed slightly, too much of the titrant, which comes from the burette, can be introduced into the solution, overshooting results.

Misreading the Volume

The accuracy of titration requires precise measurement of the volume of materials in use. But markings on a burette can be easily misread. One way to misread the volume is by looking at the measurement on an angle. From above, it can seem like the volume is lower, while from below, the apparent volume looks higher. Another source of measurement error is looking at the wrong spot. A solution forms a concave curve and the bottom of the curve is used to measure the volume. If the reading is taken from the higher sections of the curve, the volume measurement will be in error.

Concentrations

Errors in concentrations directly affect the measurement accuracy. Errors include using the wrong concentration to begin with, which can occur from chemical decomposition or evaporation of fluids. The solution may have been prepared incorrectly or contaminatns could have been introduced into the solution, such as using dirty equipment. Even the process of cleaning your equipment, if carried out with the wrong solution, can affect the concentrations of the solutions to be experimented on.

Using the Equipment Incorrectly

You must follow strict guidelines in handling and using all equipment during the experiment as the slightest mistake can create errors in the findings. For example, swirling the solution can result in loss of solution that will affect results. Errors in filling the burette can cause air bubbles that affect the flow of the liquid in the burette.

Other Errors

Other human or equipment errors can also creep in. Human error includes using selecting the wrong reagents or using the wrong amount of indicator. Equipment error typically is in the burette, which can develop leaks over time. Even a small loss of fluid will affect the results of the titration.

Error is the amount of deviation in a physical quantity that arises as a result of the process of measurement or approximation. Another term for error is uncertainty.

Physical quantities such as weight, volume, temperature, speed, or time must all be measured by an instrument of one sort or another. No matter how accurate the measuring tool—be it an atomic clock that determines time based on atomic oscillation or a laser interferometer that measures distance to a fraction of a wavelength of light some finite amount of uncertainty is involved in the measurement. Thus, a measured quantity is only as accurate as the error involved in the measuring process. In other words, the error, or uncertainty, of a measurement is as important as the measurement itself.

As an example, imagine trying to measure the volume of water in a bathtub. Using a gallon bucket as a measuring tool, it would only be possible to measure the volume accurately to the nearest full bucket, or gallon. Any fractional gallon of water remaining would be added as an estimated volume. Thus, the value given for the volume would have a potential error or uncertainty of something less than a bucket.

Now suppose the bucket were scribed with lines dividing it into quarters. Given the resolving power of the human eye, it is possible to make a good guess of the measurement to the nearest quarter gallon, but the guess could be affected by factors such as viewing angle, accuracy of the scribing, tilts in the surface holding the bucket, etc. Thus, a measurement that appeared to be 6.5 gal (24.6 l) could be in error by as much as one quarter of a gallon, and might actually be closer to 6.25 gal (23.6 l) or 6.75 gal (25.5 l). To express this uncertainty in the measurement process, one would write the volume as 6.5 gallons +/-0.25 gallons.

As the resolution of the measurement increases, the accuracy increases and the error decreases. For example, if the measurement were performed again using a cup as the unit of measure, the resultant volume would be more accurate because the fractional unit of water remain ing—less than a cup—would be a smaller volume than the fractional gallon. If a teaspoon were used as a measuring unit, the volume measurement would be even more accurate, and so on.

As the example above shows, error is expressed in terms of the difference between the true value of a quantity and its approximation. A positive error is one in which the observed value is larger than the true value; in a negative error, the observed value is smaller. Error is most often given in terms of positive and negative error. For example, the volume of water in the bathtub could be given as 6 gallons +/-0.5 gallon, or 96 cups +/-0.5 cup, or 1056 teaspoons +/-0.5 teaspoons. Again, as the uncertainty of the measurement decreases, the value becomes more accurate.

An error can also be expressed as a ratio of the error of the measurement and the true value of the measurement. If the approximation were 25 and the true value were 20, the relative error would be 5/20. The relative error can be also be expressed as a percent. In this case, the percent error is 25%.

Measurement error can be generated by many sources. In the bathtub example, error could be introduced by poor procedure such as not completely filling the bucket or measuring it on a tilted surface. Error could also be introduced by environmental factors such as evaporation of the water during the measurement process. The most common and most critical source of error lies within the measurement tool itself, however. Errors would be introduced if the bucket were not manufactured to hold a full gallon, if the lines indicating quarter gallons were incorrectly scribed, or if the bucket incurred a dent that decreased the amount of water it could hold to less than a gallon.

In electronic measurement equipment, various electromagnetic interactions can create electronic interference, or noise. Any measurement with a value below that of the electronic noise is invalid, because it is not possible to determine how much of the measured quantity is real, and how much is generated by instrument noise. The noise level determines the uncertainty of the measurement. Engineers will thus speak of the noise floor of an instrument, and will talk about measurements as being below the noise floor, or «in the noise.»

Measurement and measurement error are so important that considerable effort is devoted to ensure the accuracy of instruments by a process known as calibration. Instruments are checked against a known, precision standard, and adjusted to be as accurate as possible. Even gas pumps and supermarket scales are checked periodically to ensure that they measure to within a predetermined error.

Nearly every country has established a government agency responsible for maintaining accurate measurement standards. In the United States, that agency is known as the National Institute of Standards and Technology (NIST). NIST provides measurement standards, calibration standards, and calibration services for a wide array of needs such as time, distance, volume, temperature, luminance, speed, etc. Instruments are referred to as «NIST traceable» if their accuracy, and measurement error, can be confirmed by one of the precision instruments at NIST.

SYSTEMATIC ERROR AS THE BASIC PHYSICS AND POSSIBLE SOURCES OF SYSTEMATIC ERROR

Vinokurova Alexandra Navoi State Mining Institute alexandria08081999@mail.ru

Abstract: The article discusses the process of studying the systematic errors together with elementary physics, is considered a possible point source of systematic error and evaluate it on an international scale.

Key words: Large hadron Collider, systematic error, Metrology, low error, antimuon, event, analysis, experiment.

Science, Metrology deals with measurement methods and means of ensuring of their unity and ways of achieving the required accuracy. And in this science necessarily present concepts such as accuracy, sensitivity, graduation, accuracy class, measurement range, measurement range, calibration of measuring instruments, calibration of measuring instruments and many other scientific terms. But the most basic, important and considered to be the bread of Metrology is the notion of «error». Because the margin of error describes the precision of the measurements. And engineer-Metrology for many years working with the exception of any errors in measuring instruments. And error at the moment klassificeret on the following: relative, absolute, random, rough, systematic, given, static, instrumental, dynamic, additive, main, additional, multiplicative, and others. But I will focus on systematic errors as it is in itself contains a very strong character compared to the other. Systematic error detected experimentally and try to avoid it, not only many proven methods, but has not been validated. If bias cannot be excluded, it calculate until the beginning of the measurement and the measurement result shall be amended accordingly. Improvement of methods of measurement, the use of high quality materials, current technology allows in practice to eliminate systematic errors, so that the processing results of observations of their presence are often not reckoned.

Systematic error (or, in the physical jargon, taxonomy) characterizes the imprecision of measuring instruments or the method of data processing. More specifically, it shows our limited knowledge of this inaccuracy: after all, if the device or instrument «lying», but we know how much we will be able to adjust his testimony and eliminate the instrumental uncertainty of the result. The word «systematic» means that measurement can be repeated for the installation of millions of times, but if she has «no aim», you systematically will receive a value different from true.

Any developing science needs young enthusiasts who are in love with her and ready to devote his life. But science is a «person» is very serious and demanding. Her one love is not enough. She wants among his fans, only those who could and could reciprocate.

Currently, scientific activities are engaged in more than 10,000 scientists from all over the world at the Large Hadron Collider(LHC). Sophisticated device for the study and discovery of new physics, heavy ions, supersymmetry, big Bang theory, dark energy, dark matter, and finally energy production in large capacities and quantities. We know, for example, that electric power has one big disadvantage, no accumulation of this energy.

Modern Collider experiment is very complicated. It is a huge number of sources of systematic errors at various stages of obtaining experimental results. Here are some of them.

Errors can occur at the level of «iron», upon receipt of raw data:

• broken or defective registered separate components or sensing elements. In the detector the millions of individual components, and even if 1% of them okazalsya working, it may degrade the accuracy and «heat» detector, and the clarity of the signal. It must be emphasized that, even if you run the detector is working at 100%, the continuous detection of particles over time causes failure of individual components, so that to monitor the behavior of the detector is absolutely necessary;

• the presence of «blind spots» of the detector; for example, if the particle flies close to the axis of the beams, it will go out the window and the detector simply do not notice.

Errors can occur at the stage recognition of raw data into a physical event:

• the error in the measurement of particle energies in the calorimeter;

• error in the measurement of the particle trajectories in the tracking detectors, which inaccurately measured point of departure and momentum of a particle;

• incorrect identification of the type of particles (for example, the system failed to recognize the trace of n-meson and mistook it for K-meson). Another more subtle possibility: incorrect Association of the hadrons in one hadron jet and a wrong assessment of its energy;

• incorrect counting of the number of particles (two particles accidentally flew so close to each other that the detector saw only one trail and found them in one).

Finally, the new systematic errors are added in the later stage of the analysis events:

• the inaccuracy in the measurement of the luminosity of the beams, which affects the conversion of the number of events in the cross section of the process;

• the presence of foreign process of birth of particles, which differ from a physical point of view, but, unfortunately, look for a detector are the same. Such

processes give rise to irreducible background, which often prevents to see the desired effect;

• the need to simulate the processes (especially hadronization, the transformation of quarks into hadrons), based partly on theory, partly on past experiments. The imperfection of both introduces inaccuracies in the new experimental result. For this reason, the theoretical error is also often referred to as taxonomy.

In some cases, there are sources of systematic errors that manage to get in all categories, they combine both the properties of the detector hardware, and methods of data processing and interpretation. For example, if you want to compare with each other the number of born particles and antiparticles of some species (e.g., muon and antimuon), you do not forget that your detector consists of matter and not of antimatter! This bias towards matter can lead to the fact that the detector will see fewer muons than antimuons.

The whole sources of potential problems it is necessary to recognize and assess their impact on the performed analysis. There is absolutely no universal algorithms; the researcher must understand what errors you should pay attention and how to evaluate them. Of course, then come to the aid of the different calibration measurements done in the first two years of operation of the detector, and the simulation program that allow you to virtually test the behavior of the detector in various conditions. But the main thing in this art is the physical intuition of the experimenter, his qualifications and experience.

Careless assessment of systematic errors can lead to extremes, and very undesirable.

Low error — that is, the unjustified confidence of the experimenter that the error in the detector are small, although they are actually much more — is extremely dangerous because it can lead to completely incorrect scientific conclusions. For example, the experimenter may on that basis decide that the measurements differ from theoretical predictions at the level of statistical significance of 10 standard deviations, although the true cause of the discrepancy may simply be that he overlooked source of error, 10 times increases the measurement uncertainty and no discrepancy is actually there.

To combat this danger is the temptation to fall into the other extreme: «what if there is still any error? Maybe we have not considered? Why don’t we in any case will increase the error of measurement of 10 times for greater security.» This extreme is bad because it defeats the whole dimension. Unnecessarily overestimating the error, you risk to get a result, which will, of course, correct, but very vague, no better than the results that were already obtained to you at a much more modest installations. This approach, in fact, negates all the work on the development of

technologies for the manufacture of components for the Assembly of detector, all the costs of its work and results analysis.

Competent and responsible analysis of the systematics needs to keep the optimal balance (maximum reliability with maximum scientific value), avoiding such extremes. This is a very delicate and complicated work, and the first page in most modern articles on experimental particle physics is devoted to a thorough discussion of systematic (and statistical) errors.

Of course, systematic errors want to take control. Since this is a purely instrumental effect, the responsibility for this lies entirely with the experimenters who collected, configured and running on this installation. They make every effort to ensure that, first, to correctly detect these errors, and second, to minimize them. In fact, they begin to engage with the first days of operation, even when there is actually a scientific research program and has not begun.

References

1. Mode of access: https://tech.wikireading.ru

2. E.N. Aksenova. Elementary methods of estimation of errors of results of direct and indirect measurements

3. Mode of access: https://studopedia.su

One of the major research aspects of laboratory science is physical and chemical testing; and its test findings are the primary scientific basis for assessing product quality. Physical and chemical laboratory experiments include three primary sources of error: systematic error, random error and human error. These sources of errors in lab should be studied well before any further action.

So, what are the particular sources of each error?

The reliability of physical and chemical testing has been significantly impaired; by equipment, samples, instruments, lab environment, reagents, operating procedures and other factors; leading to many errors in physical and chemical testing.

System Error in laboratory experiments

Systematic error applies to repeated measuring of the same object under repeated conditions of measurement. The amount of the error value is either positive or negative; which is called the fixed system error in laboratory experiments and laboratory tests. Or the error changes show a certain law; which is also called the variable system error, as the measurement conditions varies.

The systemic sources of error is caused primarily by:

• The incorrect method of measurement in laboratory experiments
• The incorrect method of using the instrument in laboratory experiments
• The failure of the measuring instrument in laboratory experiments
• The performance of the testing tool itself in laboratory experiments
• The inappropriate use of the standard material and the changing environmental conditions in laboratory experiments

With certain steps and proper Laboratory Equipment these sources of errors can be minimized and corrected.

Different types of system errors are:

Method error in laboratory experiments

The method error in laboratory experiments refers to the error created by the very process of physical and chemical examination. This error is inevitable so often the test result is low or high.

For example, the dissolution of the precipitate is likely to trigger errors while conducting gravimetric analysis in physical and chemical tests; there is no full reaction during the titration, or a side reaction occurs due to the incoherence of the end point of the titration with the metering level.

Instrument error in laboratory experiments

The instrument error in test labs is caused primarily by laboratory instrument inaccuracy. If the meter dial or the zero point is inaccurate, for instance; the measurement result would be too small or too big. Unless the adjustment is not done for too long, the weighing error will eventually occur. The glass gauge has not undergone standard and scale testing; so it is used after purchasing from the manufacturer, which will allow the instrument error to occur.

Reagent error in laboratory experiments

The reagent error in lab test is caused primarily by the impure reagent or the inability to meet the experimental provisions; such as the existence of impurities in the reagent used in the physical and chemical testing phase; or the existence of contaminated water or reagent contamination that may influence the results of the examination; or the storage or operating climate. Changes in reagents and the like can cause errors in reactants.

Random Error in laboratory experiments

Error caused by various unknown factors is known as random error. This error poses erratic changes at random, primarily due to a variety of small, independent, and accidental factors. The random error is atypical from the surface. Since it is accidental, the random error is often called unmeasurable error or accidental error.

Statistical analysis can also measure random sources of error in lab, unlike systemic errors; and it can also determine the effect of random errors on the quantity or physical law under investigation. To solve random errors, scientists employ replication. Replication repeats several times a measurement, and takes the average.

Although, it should be noted that in the usual physical and chemical testing phase, which has some inevitability, both the systematic error and the random error do exist. The disparity in results caused by the inspection process mistake of the usual physical and chemical inspection personnel, incorrect addition of reagents, inaccurate procedure or reading, mistake in measurement, etc., should be considered “error” and not an error.

Thus, if there is a significant difference between repeated measurements of the same measuring object; whether it is caused by “error” should be considered. in such situation, the source of error in lab should be examined carefully, and its characteristics should be calculated.

An Example of some random sources of errors in lab

Example for distinguishing between systemic and random errors is; assuming you are using a stop watch to calculate the time needed for ten pendulum oscillations. One cause of error in starting and stopping the watch is your reaction time. You may start soon and stop late during one measurement; you can reverse those errors on the next.

These are accidental errors, since all cases are equally probable. Repeated tests yield a sequence of times, all slightly different. In random they differ around an average value. For example, if there is also a systemic mistake, your stop watch doesn’t start from zero; so the calculations will differ, not about the average value, but about the displaced value.

In this example both random and systemic source of errors in lab explained.

Human Error in laboratory experiments

The human error in laboratory experiments and lab tests primarily refers to the mistake in physical and chemical inspection phase caused by the factors of the inspector; particularly in the following three aspects:

Operational error in laboratory experiments

Operational error applies to the subjective factors in regular activity of the physical and chemical inspectors. For instance, the sensitivity of the inspector to observing the color would result in errors; or there is no effective protection when weighing the sample, so that the sample is hygroscopic.

When washing the precipitate, there is an error in the absence of appropriate washing or extreme washing; Throughout the burning precipitation, did not regulate temperature; Unless the burette is not rinsed in the physical and chemical testing process before the liquid leakage, the liquid hanging phenomenon will occur which will allow the air bubbles to linger at the bottom of the burette after the liquid is injected; Inspectors looking up (or down) the scale at the time of the degree would cause errors.

Subjective error in laboratory experiments

Subjective errors are caused mainly by the subjective considerations of physical and chemical test analysts. For example, because of the difference in the degree of sharpness of color perception, some analysts believe the color is dark when the color of the titration end point is discriminated against, but some analysts think the color is brighter;

Because the angles from which the scale values are read are different, some analysts feel high while some analysts feel low in situations. Moreover, many observers would have a “pre-entry” tendency in the actual physical and chemical inspection job, that is, subjectively unconsciously biased towards the first measurement value whenever reading the second measurement value.

Negligible error in laboratory experiments

Negligible error refers to the mistake caused during the physical and chemical examination by the inspector’s reading mistake, operation error, measurement error etc. A individual can, for example, record an incorrect value, misread a scale, forget a digit while reading a scale, or record a calculation, or make a similar blunder.

Errors can lead to incorrect results, and knowing the sources of error in lab will help us mitigate error occurrence and increase test results quality.

Задания

1. Найдите в
тексте соответствия для следующих слов
и выражений:

прибор для измерения
давления, повредить печать, в состоянии
покоя, на запястье со стороны ладони,
показать число биений (пульса) в минуту,
соблюдать полярность, открыть отделение
для батареек, закрепить манжет, слишком
туго или свободно, обеспечить точное
измерение, неотъемлемая составная
часть, журнал учета, обернуть манжету
вокруг запястья, источник энергоснабжения,
снять и повторно надеть, накачивание
манжеты (воздухом), воздух автоматически
скачивается, застегнуть застежкой с
«липучкой», вставить батарейку, закатать
рукав, автоматически отключиться,
проверка прибора на точность,
соответствовать международным стандартам
качества.

2. Выполните
лингво-переводческий анализ текста по
схеме:

Реципиент:

• индивидуальный,

• групповой,

• коллективный
  (массовый).

Источник –
анонимный/авторский:

• индивидуально-авторский,

• индивидуально-групповой,

• коллективный.

КОММУНИКАТИВНОЕ
ЗАДАНИЕ ТЕКСТА

Виды информации
(с указанием преобладающего вида)

а) когнитивная,

б) оперативная (=
апеллятивная),

в) эмоциональная,

г) эстетическая
(как подвид
эмоциональной информации).

СРЕДСТВА РЕЧЕВОГО
ОФОРМЛЕНИЯ:

• на уровне текста
  (когезия, темпоральность/атемпораль-ность,
  тип модальности);

• на уровне предложения
  (полносоставность предложения,
  тема-рематическое членение, семантика
  подлежащего, номинативность/вербальность
  высказывания, наличие пассивных
  конструкций);

• на уровне слова
  и словосочетания (термины,
  фразео-логизмы, пословицы, клишированные
  метафоры,
  сравнения и т.п.).

1. Установите, какие
   части текста представляют собой
   сообщение сведений, а какие – предписание
   действий.

2. Выявите
   систему языковых средств, оформляющих
   текст инструкции.

3. Определите, есть
   ли в тексте:

• термины,

• клише,

• прецизионная
  лексика.

1. Выполните письменный
   перевод текста на русский язык, соблюдая
   специфику данного жанра.

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