Common terms in instrumentation

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Performance characteristic: Parameters related to the functions and capabilities of instruments, along with their quantitative expressions. Reference performance characteristic refers to the performance characteristics achieved under reference operating conditions. Range is an interval of a quantity defined by upper and lower limits. Note: “Range” is usually accompanied by modifiers. For example: measurement range, scale range. It can be applied to the measured quantity or operating conditions, etc. Measuring range: The range of the quantity being measured that can be determined with the specified accuracy. Measuring range lower limit: The minimum value of the quantity being measured, as determined by the specified accuracy standard. Measuring range higher limit: The maximum value of the quantity being measured, as determined by the specified accuracy standard. The span is the algebraic difference between the upper and lower limits of a range. For example: when the range is from -20°C to 100°C, the scale is 120°C. A scale consists of a set of ordered scale marks that form part of an indicating device, along with all the relevant numbers. The scale range is the range defined by the starting value and the ending value of the scale. A scale mark is a scale line or other marking on a measuring device that corresponds to one or more specific measured values. Note: For digital readings, the digits themselves are equivalent to the scale markings. Zero mark, zero scale mark; synonym: zero scale line. A scale mark or scale line on the dial (plate) that is marked with the number “zero”. Scale division: the scale portion between any two adjacent scale marks. The value of scale division, also known as the division value. In a scale, it refers to the difference between the measured values corresponding to two adjacent scale marks. Scale spacing refers to the length of a scale division, that is, the distance between the centers of any two adjacent scale marks measured along the same line segment that represents the scale length. The scale length is, on a given scale, the length of the line segment passing through the midpoints of all the shortest marks, between the starting and ending scale marks. Note: This line segment can be a real or imaginary curve or straight line. Minimum scale value: the measured value corresponding to the marker of the scale starting point. Scale endpoint value: the measured value corresponding to the scale endpoint marker. Scale numbering refers to the set of numbers marked on a scale; they correspond to the value being measured as determined by the scale marks, or they simply indicate the numerical order of the scale marks. Linear scale: a scale in which the distance between adjacent divisions is in a constant proportional relationship with the corresponding values of those divisions. Note: A linear scale with a constant spacing between scale divisions is called a regular scale. Nonlinear scale: a scale in which the spacing between various scale intervals is not in a constant proportional relationship with the corresponding interval values. Note: Some nonlinear scales have specific names, such as logarithmic scale and square-law scale. Suppressed-zero scale: a scale that does not include a scale value corresponding to the zero value of the quantity being measured. For example: the scale of medical thermometers. An expanded scale is a scale in which, within its range, the disproportionately large portions account for most of the scale’s length.