Commonly Used Terms of Valves (II)

51. The absolute error
 
It refers that the absolute error measurement results minus the measured (agreed) true value.
 
52. Relative error
 
The absolute error is divided by the measured (agreed) true value.
 
53. Random error
 
In the process of multiple measurements of the same measurement, the change is a part of the unpredictable measurement error.
 
54. Systematic error
 
The error that the absolute value and sign remain the same or change according to a fixed rule when the conditions change in the process of measuring the same quantitative value several times under the same conditions.
 
55. Correction value
 
In order to obtain the corrected result, the value that must be added to the uncorrected measurement result by the algebraic method is the opposite value of the known part of the system error.
 
56. Correction factor
 
A numerical factor multiplied by uncorrected measurement results to compensate for systematic errors.
 
57. Arithmetic mean
 
The quotient is obtained by dividing the algebraic sum of n measurements of a quantity by n.
 
58. Performance characteristics
 
Under static or dynamic conditions or as the result of specific tests, it refers to the relevant parameters of the function and capability of the device and their quantitative expressions are determined.
 
59. Reference performance characteristics
 
It refers to performance characteristics obtained under reference working conditions.
 
60. Scope
 
It refers to the numerical range defined by the upper and lower limits of the quantity studied.
 
Note: The term "scope" is usually modified. For example, it can be applied to measured variables or working conditions.
 
61. Measuring range
 
It refers to the interval determined by two measured values measured with specified accuracy.
 
62. Lower limit of measuring range
 
It refers to the lowest value of the measured variable that the device can adjust to and measure according to the specified accuracy.
 
63. Upper limit of measuring range
 
It refers to the highest value of the measured variable that the device can adjust to and measure according to the specified accuracy.
 
64. Range
 
It refers to the algebraic difference between the upper and lower limits of a given range. For example, when the range is﹣20℃ to 100℃, the range is 120℃.
 
65. Scale
 
It refers to an ordered set of scale marks and all related numbers forming part of the indicating device.
 
66. Scale range
 
It refers to the range defined by the start point value and the endpoint value of the scale.
 
67. Linear scale
 
It refers to a scale in which the spacing between cells is in constant proportion to the corresponding cell value.
 
Note: The linear scale with the constant intervals between scales is called a regular scale.
 
68. Nonlinear scaling
 
It refers to a scale with a non-constant proportional relationship between the cell spacing of each scale and the corresponding cell value.
 
Note: Some nonlinear scales have special names, such as logarithmic scale and square law scale.
 
69. Zero position of measuring instrument
 
When any auxiliary energy required by the working of the measuring instrument is connected and the measured value is zero, the instrument directly indicates the value.
 
70. Instrument constant
 
In order to obtain the indication value of the measuring instrument, a coefficient must be multiplied by the direct indication value.
 
Note: When the directly indicated value is equal to the measured value, the constant of the measuring instrument is 1.
 
71. Characteristic curve
 
It refers to a curve that shows the functional relationship between the steady-state value of the output variable of a system or device and one input variable. At this time, all other input variables are kept at the prescribed constant value.
 
Note: When other input variables are treated as parameters, a set of characteristic curves can be obtained.
 
72. Adjustment
 
It refers to the operation of making the output of a device or instrument as consistent as possible with the expected specified characteristic curve.
 
73. Calibration
 
It refers to a set of operations that establish the relationship between the measured value and the corresponding output value of the device under specified conditions.
 
74. Calibration curve
 
It refers to a curve showing the relationship between the measured value and the corresponding value actually measured by the device under specified conditions.
 
75. Sensitivity
 
It measures the change of meter response divided by the corresponding excitation change.
 
76. Accuracy
 
It refers to the consistency between the measured result and the measured (agreed) true value.
 
77. Accuracy limit
 
It refers to the limit value of the specification that can guarantee the inaccuracy of a specific type of device.
 
78. Basic error
 
Also known as inherent error, It refers to the indication error of the instrument under the reference condition.
 
79. Consistency
 
It refers to the coincidence degree when the calibration curve is close to the specified characteristic curve (straight line, logarithmic curve, parabola, etc.).
 
80. Consistency error
 
It refers to the absolute value of the maximum deviation between the calibration curve and the specified characteristic curve.
 
81. linearity
 
It refers to the coincidence degree when the calibration curve is close to the specified straight line.
 
82. Linearity error
 
It refers to the absolute value of the maximum deviation between the calibration curve and the specified straight line.
 
83. Dead zone
 
It refers to a finite numerical range in which the change of input variables does not cause any perceptible change in output variables.
 
84. Stability
 
Under the specified working conditions, it refers to the ability of instrument performance characteristics to remain unchanged within the specified time.
 
85. Reliability
 
It refers to the ability of the device to complete the specified function under the specified conditions and within the specified time.
 
86. Drift
 
Over a period of time, it refers to the input-output relationship of the device changing gradually, which is not caused by external influences acting on the device.
 
87. Spot drift
 
It refers to the output change corresponding to a constant input within a specified time under a specified reference working condition.
 
88. Zero drift
 
Referred to as zero drift, it refers to the point drift on the lower limit of the range. When the lower limit value is not zero, it is also called starting point drift.
 
89. Repeatability
 
Under the same working condition, it refers to the consistency between the output values measured by the instrument for the same input value in the same direction several times in a row.
 
Note: Repeatability should not include backlash and drift.
 
90. Repeatability error
 
Under the same working conditions, when moving from the same direction in the whole range, it refers to the algebraic difference between the limit values obtained by continuously measuring the output of the same input value many times in a short time.
 
91. Range error
 
It refers to the difference between the actual output range and the specified output range.
 
Note: The range error is usually expressed as a percentage of the specified output range.
 
92. Span shift (offset)
 
It refers to the change in output range caused by some influence.
 
90. Zero error
 
Under the specified use conditions, it refers to the difference between the actual output value and the lowest value of the specified output range when the input is at the lower limit of the range.
 
Note: The zero error is usually expressed as a percentage of the specified output range.
 
94. Zero point migration (offset)
 
When the input is at the lower limit of the range, it refers to the change of the output value caused by some influence.
 
Note: Zero shift is usually expressed as a percentage of the specified output range.
 
95. Indication error
 
It refers to the indicated value of the instrument minus the measured (agreed) true value.
 
96. Citation error
 
It refers to the indication error of the instrument divided by the specified value.
 
Note: This specified value is often referred to as a reference value. For example, it can be the measuring range or the upper limit value of the instrument.
 
97. Average time between failures
 
During the rated life of the functional unit, under the specified conditions, it refers to the average value of the time length between adjacent failures.
 
98. Average repair time
 
It refers to the average time required for troubleshooting.
 
99. Failure
 
It refers to the termination of the ability of a functional unit to achieve its prescribed function.
 
100. Fault
 
It refers to an unexpected state that causes a functional unit to fail to achieve its specified function.
 
101. Function
 
It refers to the purpose or action accomplished by the device.
 
102. Sampling
 
It refers to the process of taking the measured values at certain time intervals.
 
103. Sampling rate (speed)
 
It refers to the frequency of sampling the measured data, that is, the sampling times per unit time.
 
104. Sampling period
 
It refers to the interval time of secondary measurement in the periodic sampling control system.
 
105. Scan
 
Sampling several variables periodically in a predetermined way. The function of the scanning device is usually used to determine the state or value of variables.
 
106. Scan rate
 
It refers to the access rate of a series of analog input channels expressed in the number of input channels per second.
 
107. Dead time with time delay
 
It is also known as death. It refers to the time from the moment when the input quantity changes to the moment when the instrument output quantity starts to change.
 
108. Time constant
 
In a first-order linear system caused by step or pulse input, it refers to the time required for the output to complete 63.2% of the total increase or decrease.
 
109. Damping
 
It refers to the dissipation of system energy in motion.
 
110. Periodic damping, under damping
 
It is also known as under-damping, the damping of overshoot in step response.
 
111. Aperiodic damping, overdamping
 
It is also called overdamping, damping without overshooting in step response.
 
112. Damping factor
 
In the free oscillation of a second-order linear system, it refers to the ratio of the larger amplitude to the smaller amplitude of a pair of (opposite) continuous oscillations near the final steady-state value output.
 
113. Noise
 
It refers to the harmful disturbance that causes its components to be concealed on the superimposed signal.
 
114. Input impedance
 
It refers to the impedance between instrument inputs.
 
115. Output impedance
 
It refers to the impedance between instrument outputs.
 
116. Load impedance
 
It refers to the total impedance of all devices and connecting wires connected to the output of the instrument.
 
 
99 Technical Terms of DCS Control System