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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 associated 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 mark on an instrument 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 a 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, length of a scale division: The distance between the centerlines of any two adjacent scale marks, measured along the same line segment representing the length of the scale. 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 scale starting point marker. Scale endpoint value: the measured value corresponding to the scale endpoint marker. Scale numbering refers to the set of numbers marked on a scale; these numbers correspond to the value being measured as determined by the scale markings, or they simply indicate the numerical order of the scale markings. 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 in which the spacing between scale divisions is constant is called a regular scale. Nonlinear scale: a scale in which the spacing between various scale divisions is not in a constant proportional relationship with the corresponding division 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 disproportionate expanding portion accounts for most of the scale’s length. The zero point of a measuring instrument is the direct indication given by the instrument when all auxiliary energy sources required for its operation are turned on and the quantity being measured is zero. ①When measuring instruments use an auxiliary power supply, this term is usually referred to as \"electrical zero point\". ②The term \"mechanical zero\" is often used when any auxiliary power supply for the instrument is disconnected and it is not in operation. The instrument constant is a coefficient that must be multiplied by the direct reading in order to obtain the indicated value of a measuring instrument. Note: When the direct reading is equal to the value being measured, the constant of the measuring instrument is 1. A characteristic curve is a curve that shows the functional relationship between the steady-state value of an instrument’s output and one input quantity, while all other input quantities are kept at specified constant values. The specified characteristic curve is a curve that, under specified conditions, shows the functional relationship between the steady-state output value that an instrument should exhibit and a certain input value. Adjustment refers to the operations carried out to bring instruments and meters into a normal working state and to eliminate any deviations, so that they can be used properly. User adjustment: the adjustments that users are allowed to make. Calibration is the process of establishing, under specified conditions, the relationship between the reading indicated by a measuring instrument or system, or the value represented by a physical measuring tool, and the known value corresponding to the quantity being measured. A calibration curve is a curve that, under specified conditions, represents the relationship between the value to be measured and the value actually measured by the instrument. Calibration cycle: A combination of the upward calibration curve and the downward calibration curve within the limits of the calibration range for instruments. A calibration table refers to the data table format of a calibration curve. Traceability: A property of measurement results that allows them to be linked to appropriate reference standards (usually international reference standards or **standard instruments**) through a continuous chain of comparisons. Sensitivity is the ratio of the output change of a measuring instrument to the corresponding input change. Accuracy: The degree to which the indicated value of an instrument or meter corresponds to the true value of the quantity being measured. Accuracy class: The grades into which instruments are classified based on their level of accuracy. Limits of error: Synonyms include maximum permissible error. These are the limits on the error of instruments as specified by standards, technical specifications, etc. Intrinsic error, also known as inherent error. The indication error of the instruments under reference conditions. Conformity refers to the degree of agreement between a standard curve and a specified characteristic curve (such as a straight line, logarithmic curve, parabola, etc.). Note: Consistency is divided into independent consistency, terminal consistency, and case-based consistency. When only consistency is mentioned, it refers to independent consistency. Independent conformity refers to the degree of consistency achieved by adjusting the calibration curve so that it approaches the specified characteristic curve, with the maximum deviation being minimized. Terminal-based conformity refers to the degree of consistency achieved by rapidly bringing the calibration curve close to the specified characteristic curve, such that the upper and lower limits of both curves coincide. Zero-based conformity refers to the degree of consistency achieved by making the calibration curve match the specified characteristic curve through adjustments, such that the lower limits of the ranges of both curves coincide and the maximum positive and negative deviations are equal. Conformity error: the maximum deviation between the calibration curve and the specified characteristic curve. ①Consistency errors are divided into independent consistency error, terminal consistency error, and zero-based consistency error; when only the term \"consistency error\" is used, it refers to the independent consistency error. ②Consistency error is usually expressed as a percentage of the range. Linearity refers to the degree of consistency between a calibration curve and a specified straight line. Note: Linearity is divided into independent linearity, terminal linearity, and zero-based linearity. When only linearity is mentioned, it refers to independent linearity. Independent linearity refers to the degree of consistency achieved by bringing the calibration curve as close as possible to a specified straight line at high speeds, thereby minimizing the maximum deviation. Terminal-based linearity is the degree of agreement achieved by adjustment, whereby the calibration curve is made to closely follow a specified straight line, with the upper and lower limit values of both curves coinciding respectively. Zero-based linearity refers to the degree of consistency achieved by making the calibration curve as close as possible to a specified straight line, such that the lower limits of their ranges coincide and the maximum positive and negative deviations are equal. Linearity error is the maximum deviation between the calibration curve and the specified straight line. ①Linearity errors are divided into independent linearity error, terminal linearity error, and zero-based linearity error. When only the linearity error is mentioned, it refers to the independent linearity error. ②Linearity error is usually expressed as a percentage of the range. The dead band is the maximum range of input variation that does not cause any noticeable change in the output of the instrument. Discrimination: The ability of instruments to respond to slight changes in input values. Discrimination threshold: the minimum input change that causes a perceptible change in response from the instrument. For example, if the smallest load change that causes a visible displacement of the balance pointer is 90 mg, then the balance’s resolution threshold is 90 mg. Resolution is the ability of an instrument’s indicating device to meaningfully distinguish between two adjacent values of the quantity being indicated. Stability refers to the ability of an instrument’s performance characteristics to remain unchanged over a specified period of time under defined operating conditions. Drift refers to the slow change over time in the input–output characteristics of instruments and meters. Point drift refers to the change in output over a specified period of time, for a constant input, under specified operating conditions. Zero drift, also simply referred to as zero drift, is the drifting at the lower limit of the range. When the lower limit is not zero, it is also referred to as starting-point drift. Repeatability refers to the degree of consistency among the output values obtained by an instrument when it measures the same input value multiple times in the same direction under identical working conditions. Note: Repeatability should not include hysteresis and drift. Repeatability error is the random error obtained from conducting multiple consecutive measurements of the same input value in the same direction, over the entire measurement range and under the same operating conditions. Span error is the difference between the actual output range and the specified output range under reference operating conditions. It is usually expressed as a percentage of the specified output range. Span shift (offset) is a change in the output range caused by certain influencing factors. Zero error refers, under reference operating conditions, to the difference between the actual output value when the input is at the lower limit of the range and the specified lower limit of the output range. When the lower limit is not zero, it is also referred to as the starting-point error. Zero shift: The change in the output value that occurs when the input is at the lower limit of the range, due to certain influencing factors. When the lower limit is not zero, it is also referred to as origin shift (offset). Error of indication: the reading given by a measuring instrument minus the true value of the quantity being measured. Reference error/fiducial error: the reading error of a measuring instrument divided by the specified value. Note: This specified value is often referred to as a reference value; for example, it can be the range or upper limit of an instrument’s measurement capacity. Sampling is the process of taking values of a measured quantity at certain time intervals. The sampling rate is the frequency at which measurements are taken, that is, the number of samples per unit of time. Sampling time: the time at which the measured value is detected during the sampling process. The scan rate is the sampling rate for a series of analog input channels, expressed as the number of input channels per second. Warm-up period/time: The time required for an instrument or device to reach its specified performance indicators after being powered on. Input impedance refers to the impedance between the input terminals of a measuring instrument. Output impedance: The impedance between the output terminals of an instrument. The load impedance is the sum of the impedances of all devices connected to the output terminal of the instrument, as well as those of the connection wires. Power consumption: the maximum electrical power required by an instrument within its operating range under steady-state conditions. Air consumption: The maximum flow rate of gas consumed by instruments and meters within their operating range under steady-state conditions. Operating influence: The change in the performance of an instrument that occurs when, with all other operating conditions remaining constant, a certain value under the reference operating conditions is changed to a specified value under normal operating conditions. ①Typically, the upper and lower limits under normal operating conditions are used as the specified values. ②If the relationship between working conditions and their changes is non-linear, coefficients can be specified for different ranges; for example, a range of 220V to 230V corresponds to a coefficient of 0.01% per V ； From 230V to 240V, it is 0.15% per volt. Response characteristic: Under specified conditions, the relationship between the input quantity and the corresponding output quantity. ①This relationship can be established on the basis of theoretical or experimental research, and it can be expressed in the form of algebraic equations, numerical tables, or graphs. ②When the variation of the input is a function of time, one form of the response characteristics is the transfer function. Time response: A specified change in the input quantity causes a corresponding change in the output quantity over time. Step response: The time response caused by a step change in the input value. Ramp response: The time response resulting from the slope of a changing input value increasing abruptly from zero to a certain finite value. The impulse response is the time response induced by applying an impulse function to an input.