2.5G, which stands for “second and a half generation,” is a cellular wireless technology developed in between its predecessor, 2G, and its successor, 3G. “2.5G” is an informal term, invented solely for marketing purposes, unlike “2G” or “3G” which are officially defined standards based on those defined by the International Telecommunication (ITU). The term “2.5G” usually describes a 2G cellular
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Calibration: If a known input is given to the measurement system the output deviates from the given input, the corrections are made in the instrument and then the output is measured. This process is called “Calibration”. Sensitivity: Sensitivity is the ratio of change in the output signal to the change in the input signal. Readability: Refers to the ease with
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Errors in Measurement : Error = Measured Value – True Value Em = Vm – Vt 1. Absolute Error : True absolute error : = Result of measurement – True Value Apparent Absolute error : = Result of measurement – Arithmetic Value 2. Relative error : It is defined as the results of the absolute error and the
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Failure Mode – A particular way in which an item fails, independent of the reason for failure. Failure Mode and Effects Analysis (FMEA) – A procedure by which each credible failure mode of each item from a low indenture level to the highest is analyzed to determine the effects on the system and to classify each potential failure mode in
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CRITICALITY is a measure of the frequency of occurrence of an effect. – May be based on qualitative judgement or – May be based on failure rate data (most common) Qualitative analysis: –Used when specific part or item failure rates are not available. Quantitative analysis: –Used when sufficient failure rate data is available to calculate criticality numbers. Qualitative Approach: Because
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It is defined as the probability that a given system will perform it’s function adequately for it’s specified period of lifetime under specified operating conditions. Common measures are : 1. Failure rate. 2. Mean time between failures(MTBF) 3. Survival percentage. Failure Rate: Rate which components of population fail. R(t)=Ns(t)/Nf(t) Where, Ns(t)- No. of components that survived during time ’t’ Nf(t)
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MEASUREMENTS: A Measurement is the outcome of an opinion formed by observers about some physical quantity. CLASSIFICATION OF MEASUREMENTS: Standards – ( Reproduce the value of given quantity ) Fixed Gauges – (Check Dimensions) Measuring Instruments – (Determine the measured value) NEEDS FOR MEASUREMENT: 1. To Determine the true dimensions of a part. 2. To increase our knowledge and understanding
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Interpolation The method by which contouring machine tools move from one programmed point to the next is called interpolation. This ability to merge individual axis points into a predefined tool path is built into most of today’s MCUs. There are five methods of interpolation: linear circular helical parabolic cubic All contouring controls provide linear interpolation, and most controls are capable
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Two types of programming modes, the incremental system and the absolute system, are used for CNC. Both systems have applications in CNC programming, and no system is either right or wrong all the time. Most controls on machine tools today are capable of handling either incremental or absolute programming. Incremental program locations are always given as the distance and
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The term numerical control is a widely accepted and commonly used term in the machine tool industry. Numerical control (NC) enables an operator to communicate with machine tools through a series of numbers and symbols. NC which quickly became Computer Numerical Control (CNC) has brought tremendous changes to the metalworking industry. New machine tools in CNC have enabled industry to
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