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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