Some important terminologies used in measurement
Things Should Known by Quality Engineer related measurement.
It should be noted that sensitivity is a term associated with the measuring equipment whereas accuracy and precision are association with measuring process. Sensitivity means the ability of a measuring device to detect small differences in a quantity being measured. For instance if a very small change in voltage applied to 2 voltmeters results in a perceptible change in the indication of one instrument and not in the other. Then the former (A0 is send to be more sensitive. Numerically it can be determined in this way for example if on a dial indicator the scale spacing is 1.0 mm and the scale division value is 0.01 mm then sensitivity =100. it is also called amplification factor or gearing ratio.
- By same observer
- With the same instrument
- Under the same conditions
- Without any change in location
- Without change in the method of measurement
- And the measurement is carried out in short interval of time.
- By different observer
- By different methods
- Using different instruments
- Under different condition, location and times.
- The calibration of any measuring instrument is necessary for the sake of accruing of measurement process. It is the process of framing the scale of the instrument by applying some standard (known) signals calibration is a pre-measurement process generally carried out by manufactures.
- It is carried out by making adjustment such that the read out device produces zero output for zero measured input similarly it should display output equipment to the known measured input near the full scale input value.
- If accuracy is to be maintained the instrument must be checked and recalibration if necessary.
- As far as possible the calibration should be performed under similar environmental condition with the environment of actual measurement