Measurement error

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basic presentation to the elementary category system error sources unexpected error error error error handling influence the basic description of every physical amount is one objective reality, in certain conditions with omit of the people's will the objective size, folk will call it the true value of the physical quantities. Measurement is desired to be measured to obtain the true value. However, measurements ought be based aboard a certain theory alternatively usage, the use of certain equipment in certain environments, from characteristic people. Since the existence of comparison theory, experiments, methods, complicated to perfect, the sensitivity and the aptitude to differentiate laboratory instruments have constraints, the circling context of instability and other factors, to be impossible to meter the true value is measured, the measurement results and the always exist between the true value measured just about bias, this prejudice is called measurement error. Measurement error can be divided into three categories: systematic errors, random errors, gross error. Error causes can be attributed to the following aspects. 1, 2 measuring apparatus error, environmental error of 3, 4 measurement error, the errhardly everurce of error in measuring staff go is carried out under certain conditions, the external context, the observer's skill level and building of the instrument itself is imperfect and other causes, may lead to the generation of measurement error. Usually measuring instruments, the observer's capability level and the external environment in 3 areas attach, as observing conditions. Observing conditions are no ideal and ever-changing, is the root reason of measurement error. Usually the same observation conditions the manifold observations, such as precision of observation; reconnaissance of the manifold observations in different conditions, understood as precision ranging observations. Specifically, the measurement error effectively from the following three aspects: (1) observing the environment mainly refers to external conditions in temperature, oppression, climate humidity and legibility, wind and cloudy refraction and other ingredients are constantly changing,9544.org, leading to the measurement results with error. (2) instrument conditions in the processing equipment and gathering process, the structure of the instrument can no certify to encounter all kinds of geometric relationships, such instruments will inevitably bring to the measurement error. (3) the observer's own condition as scrutinized at the senses to identify capability limitations and proficient to varying degrees, likewise the instrument of, the leveling targeting other aspects of error. Measurement error along to their shock on the nature of the measurement results can be divided into systematic errors and fortuitous errors. Categories in physics experiments, for measurement of physical quantities under test is divided into 2 categories: direct measurement and oblique measurement. Direct measurement can be measured using measuring instruments and to compare directly the results. For instance, with the scale, vernier caliper, stopwatch, poise, etc. DC ammeter measurement is direct measurement. Indirect measurement is not directly measuring instruments to measure out the size to be measured, yet to be measured with a few based on direct measurement of the sum enumerated to be a function of measurement. For example, the acceleration of gravity, the pendulum of the pendulum by measuring width and time, then the formula calculated from the pendulum period, this type of measurement is an indirect measurement. Systematic errors in the same observing conditions, the quantity of n times an observation, whether the error occurs and characters are the same size alternatively according to certain rules changes, this error is called systematic errors. System error is additive. One of the chief causes of systematic error is due to equipment manufacturing imperfections. For instance, with a nominal length of 50m from the governor to the amount, the actual length of test iron potentate 50.005 m, then every ruler, with a +0.005 m on the error (should be joined), measurement of the foot segment of the more error caused by the greater. Therefore, this error is proportional with the distance measurement. Again, the criterion of measurement, when the collimation axis is not parallel with the standards arising from the tube axis angle, the foot of the readings produced by the criterion error as the l * i arbitrage corresponding to the second value), with water level to the level l is proportional to the distance between the feet, so this error by a rule change. Systematic errors with obvious regularity, and cumulative, a magnificent influence on the measurement results. However, due to the size of systematic errors and symbols have a certain pattern, so you can take measures to eliminate or minimize their impact. Accidental errors of observation in the same conditions, on a volume are n observations, the error occurs if the importance and sign are not sure, then this error is called random error, too understood as random error. For example, using theodolite angle of collimation error, the ruler of the amount of time away from reading error, etc., are entire accidental errors. Accidental errors, in terms of their individual values, the observation before we really can not portend the size and sign of its emergence. However, if certain outlooking conditions, a certain amount of multiple observations, the error column preached a certain regularity, called statistical laws. Moreover, with the scrutinized increase in the digit, the regularity of random error is many clearer. Accidental error has the following four characteristics: ① in certain outlooking conditions, the absolute value of random error will not exceed a certain limit (in this circumstance 1.6 chances (or the probability of great); ③ utter value equal to the assured and negative errors occur an equal opportunity; ④ under the same conditions, the same amount and other precision observations, the arithmetic average of the random error, with the observed boost in the number of endless massive and tends to zero of the error measured in adding to the amount of appearance inspire, anyone amount of influence on the measurement results, which measure the system input marker in the non-informative parameter, referred to as influence quantities. electronic measurement of the amount of more and sophisticated, often can not be ignored. ambient temperature and humidity, afford voltage fluctuations and electromagnetic interference, the amount of outside influence is a typical example of clamor, nonlinearity and drift, is a typical example of the amount of internal influence, affecting the amount of often alteration over period, and this change is routinely non-stationary nature of random process, but the performance of non-stationary nature of maximum of the numerical anticipation of slower change. In addition, measuring instruments, if certain operating characteristics will affect the The other job characteristics, called the sometime affecting the properties, affecting properties can also lead to measurement error, for instance, AC voltage detector in the observation table characteristic of the different waveforms and measure the voltage by different frequencies produce different measurement error in the electronic measurement and measurement, the upon conditions are more manifest, and many random system error probability density delivery of non-normal (eg, truncated regular distribution, a rectangular uniform distribution, Simpson, triangle, trapezoid, M-shaped distribution, U-shaped distribution and Rayleigh distribution),9233.org, and even unknown distribution statute of these gave the electronic processing and estimation of measurement error caused a number of special difficulties of the error handling process of the basic method of random error is the probability of statistical methods. dealing with the premise namely systematic errors can be ignored, or its impact has been eliminated in advance or after the affirmative may be ruled out. generally trusted that random errors are numerous nameless factors affect the measurement results, it is natural, this is the central limit theorem of probability theory the inevitable outcome of reducing the error of method 1, use precision measuring instruments; 2, several measurements were averaged. 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