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Im ch 1(pt-3) error
- 2. Types of Error No measurement can be made with perfect accuracy, but it is important to find out what the accuracy actually is and how different errors have entered into the measurement. A study of errors is a first step in finding ways to reduce them.
- 3. Error is the difference between the measured value and the true value of the thing being measured. Uncertainty (惶惘惠忰悋 愃惘) is a quantification ( 擧惘悋 惠惺 擧悋 惆悋惘 ) of the doubt about the measurement result.
- 4. Re-call ..
- 8. Few Terms Related to Errors
- 18. Types of Errors
- 19. Types of Error. Errors may come from different sources and are usually classified under three main headings:- - Gross errors: largely human errors, among them misreading of instruments, incorrect adjustment and improper application of instruments, and computational mistakes. - Systematic errors: shortcomings of the instruments, such as defective or worn parts, and effects of the environment on the equipment or the user. - Random errors: those due to causes that cannot be directly established because of random variations in the parameter or the system of measurement.
- 20. Gross Errors This class of errors mainly covers human mistakes in reading or using instruments. One common gross error frequently committed by beginners in measurement work involves the improper use of an instrument. In general, indicating instruments change conditions to some extent when connected into a complete circuit, so that the measured quantity is altered by the method employed. The instrument may have a "loading effect" on the circuit being measured, altering the original situation by the measurement process.
- 21. Effect of Improper Use of instruments
- 25. Error caused by loading effect can be avoided by using high-resistance voltmeters.
- 26. Systematic Errors Systematic errors: shortcomings of the instruments, such as defective or worn parts, and effects of the environment on the equipment . This type of error is usually divided into two different categories: (1) instrumental errors, defined as shortcomings of the instrument; (2) environmental errors, due to external conditions affecting the measurement.
- 27. Systematic Errors . . . A Instrumental errors are errors inherent in measuring instruments because of their mechanical structure. For example, in the dArsonval movement friction in bearings of various moving components may cause incorrect readings. Irregular spring tension, stretching of the spring, or reduction in tension due to improper handling or overloading of the instrument will result in errors. Other instrumental errors are calibration errors, causing the instrument to read high or low along its entire scale. (Failure to set the instrument to zero before making a measurement has a similar effect.) .
- 28. Systematic Errors . . . Instrumental errors may be avoided by (1) selecting a suitable instrument for the particular measurement application; (2) applying correction factors after determining the amount of instrumental error; (3) calibrating the instrument against a standard.
- 29. Systematic Errors . . . Environmental errors are due to conditions external to the measuring device, including conditions in the area surrounding the instrument, such as the effects of temperature, humidity, barometric pressure, or of magnetic or electrostatic fields.
- 30. Random Errors These errors are due to unknown causes and occur even when all systematic errors have been accounted for. In well-designed experiments, few random errors usually occur, but they become important in high-accuracy work. This variation cannot be corrected by any method of calibration or other known method of control and it cannot be explained without minute investigation. The only way to offset these errors is by increasing the number of readings and using statistical means to obtain the best approximation of the true value of the quantity under measurement.