instrumentation and metersIntroduction to commonly used professional terms
Time constant
In a first-order linear system caused by step or pulse inputs, the time required to complete 63.2% of the total rise or fall of the output.
Rise time
For step response, the time from the moment the output signal starting from zero reaches a specified small percentage (e.g. 10%) of the final steady-state value to the moment it first reaches a specified large percentage (e.g. 90%) of that steady-state value.
Setting time
The time from the step change of the input signal to the deviation of the output signal from the final steady-state value not exceeding the specified tolerance (e.g. 1%).
Note: Instruments with indicator devices, also known as damping time, establish time.
Step response time
When the input undergoes a step change, the time it takes for the output to reach the specified percentage of the difference between the final steady-state value and the initial steady-state value for the first time from the initial value.
Ramp response time
The time required from applying a ramp input to maintaining the output within the specified tolerance band of the input value multiplied by the static gain minus the first-order steady-state deviation value of the output.
Frequency response characteristic [Figure]
The graphical representation of logarithmic gain and phase angle as a function of frequency, usually expressed in logarithmic coordinates
Scale division value of scale division
Also known as grid value.
The difference between the measured values of two adjacent scale marks in the scale.
Scale spacing, length of a scale division
The distance between the centerlines of any two adjacent scale markers measured along the same line segment representing the length of the scale.
Scale length
On a given scale, measure the length of the line segment between the starting and ending scale markers using the midpoint of all shortest markers.
Note: This line segment can be a real or imaginary curve or straight line.
Minimum scale value
The measured value corresponding to the starting point mark of the scale.
Maximum scale value
The measured value corresponding to the endpoint marker of the scale.
Scale numbering
The entire set of numbers marked on a scale corresponds to the measured value determined by the scale mark, or only represents the numerical order of the scale mark.
Zero of a measuring instrument
When any auxiliary energy required for the operation of the measuring instrument is connected and the measured value is zero, the direct indication of the instrument is obtained.
① In the case of measuring instruments using auxiliary power sources, this term is commonly referred to as' electrical zero position '.
② When any auxiliary energy source of the instrument is cut off and not working, the term 'mechanical zero position' is often used.
Instrument constant
To obtain the indication of the measuring instrument, a coefficient must be multiplied by the direct indication.
Note: When the direct indication is equal to the measured value, the constant of the measuring instrument is 1.
Characteristic curve
A curve that indicates the functional relationship between the steady-state output value of an instrument and an input quantity (with all other input quantities remaining at a specified constant value).
Specify characteristic curve in the prescribed characteristic curve
A curve indicating the functional relationship between the steady-state output value of an instrument and an input quantity under specified conditions.
Adjust the adjustment
To ensure that the instruments and meters are in normal working condition and eliminate deviations to be suitable for use.
User adjustment
Allow users to make adjustments.
Calibration
The operation of establishing the relationship between the indicated value of a measuring instrument or measuring system or the value reflected by a physical measuring tool and the known value corresponding to the measured object under specified conditions.
Calibration curve
A curve that represents the relationship between the measured value and the actual measured value of the instrument under specified conditions.
Calibration cycle
The combination of upward and downward calibration curves within the limit range of instrument calibration.
Calibration table
The data table format representing the calibration curve.
Traceability of traceability
A characteristic in which measurement results can be linked to appropriate standards (usually international or national standards) through a continuous comparison chain.
Sensitivity
The output change value of the instrument is divided by the corresponding input change value.
Precision accuracy
The degree of consistency between the readings of instruments and the measured [agreed] true values.
Accuracy class
Instruments and meters are classified into different levels based on their accuracy.
Limits of error
Synonym: maximum permissible error
The limit of instrument error specified by standards, technical specifications, etc.
Fundamental error
Also known as inherent error.
The indication error of the instrument under reference conditions.
Consistency conformity
The degree of consistency between standard curves and specified characteristic curves (such as straight lines, logarithmic curves, parabolas, etc.).
Note: Consistency is divided into * * consistency, end group consistency, and case based consistency. When referring only to consistency, it means * * consistency.
**Independent consistency
By adjusting the calibration curve to approach the specified characteristic curve, the degree of consistency is achieved when the maximum deviation is minimized.
Terminal based conformity
The degree of consistency when the upper and lower limits of the range of the two curves coincide by approaching the specified characteristic curve at high speed.
Zero based consistency
By adjusting the calibration curve to approach the specified characteristic curve, the degree of consistency is achieved when the lower limits of the two curves coincide and the maximum positive and negative deviations are equal.
Consistency error
The maximum deviation between the calibration curve and the specified characteristic curve.
① Consistency error is divided into * * consistency error, end group consistency error, and zero based consistency error. When only referred to as consistency error, it refers to * * consistency error.
② Consistency error is usually expressed as a percentage of the measurement range.
Linearity
The degree of consistency between the calibration curve and the specified straight line.
Note: Linearity is divided into * * linearity, end group linearity, and zero based linearity. When only called linearity, it refers to * * linearity.
**Independent linearity
The degree of consistency that minimizes the maximum deviation by aligning the calibration curve with the specified straight line at high speed.
Terminal based linearity
The degree of consistency when adjusting the calibration curve to approach the specified straight line, so that the upper and lower limits of the two ranges coincide.
Zero based linearity
The degree of consistency when adjusting the calibration curve to approach the specified straight line, so that the lower limits of the two ranges coincide and the maximum positive and negative deviations are equal.
Linearity error
The maximum deviation between the calibration curve and the specified straight line.
① Linearity error is divided into * * linearity error, terminal linearity error, and zero basis linearity error. When only called linearity error, it refers to * * linearity error.
② Linearity error is usually expressed as a percentage of the measurement range.
Dead band
The maximum input variation range that does not cause any noticeable changes in the output of the instrument.
Discriminative power discrimination
The response ability of instruments and meters to small changes in input values.
Discrimination threshold
The minimum input change that causes the instrument to produce a perceptible change response. For example, when the minimum load change that causes visible displacement of the balance pointer is 90mg, the discrimination force threshold of the balance is 90mg.
Resolution resolution
The instrument and meter indicator device has the ability to meaningfully distinguish between two adjacent values of the indicated quantity.
Stability and stability
The ability to maintain the performance characteristics of instruments and meters unchanged for a specified period of time under specified working conditions.
Drift drift
The slow variation of input-output characteristics of instruments and meters over time.
Point drift
The output variation corresponding to a constant input within a specified time under specified working conditions.
Zero drift
Abbreviated as Zero Drift
Point drift at the lower limit of the range. When the lower limit value is not zero, it is also called starting point drift.
Repetitive repeatability
The degree of consistency between the output values of instruments and meters that measure the same input value in the same direction multiple times under the same working conditions.
Note: Repeatability should not include hysteresis or drift.
Repeatability error
The random error obtained from multiple consecutive measurements of the same input value from the same direction within the entire measurement range and under the same working conditions.
Range error
The difference between the actual output range and the specified output range under reference working conditions. Usually expressed as a percentage of the specified output range.
Range shift (offset)
Changes in output range caused by certain influencing factors.
Zero error
Under reference working conditions, the difference between the actual output value and the specified output range lower limit value when the input is at the lower limit of the range. When the lower limit value is not zero, it is also known as the starting point error.
Zero shift (offset)
The change in output value caused by certain influencing variables when the input is at the lower limit of the range. When the lower limit value is not zero, it is also called starting point migration (offset).
Error of indication
Subtract the measured [agreed] true value from the indicated value of the instrument.
Reference error: Fiducial error
Divide the indication error of the instrument by the specified value.
Note: This specified value is often referred to as the reference value, for example, it can be the range or upper limit value of the instrument.
Sampling
The process of taking values from the measured data at certain time intervals.
Sampling rate
The frequency of sampling the measured object, which is the number of samples per unit time.
Sampling time
Detect the time being measured during the sampling process.
Scan rate
The sampling rate of a series of analog input channels, expressed as the number of input channels per second.
Warm up period, warm up time
The time required for instruments and meters to reach the specified performance indicators after being powered on.
Input impedance
Impedance between input terminals of instruments and meters.
Output impedance
Impedance between the output terminals of instruments and meters.
Load impedance
The total impedance of all devices and connecting wires connected to the output terminal of the instrument.
Electrical power consumption
At steady state, the maximum electrical power required by the instrument within its operating range.
Air consumption
At steady state, the maximum flow rate of gas consumed by the instrument within its operating range.
Working conditions affect operating influence
When all other working conditions remain constant, the performance change of the instrument caused by the change of a reference value in the reference working conditions to a specified value in the normal working conditions.
① Usually, the upper and lower limits of normal working conditions are used as the prescribed values.
② If the relationship between the influence of working conditions and changes in working conditions is nonlinear, coefficients for different intervals can be specified separately, for example: 0.01% range/V from 220V to 230V; 0.15% range/V from 230V to 240V.
Response characteristic
The relationship between input quantity and corresponding output quantity under specified conditions.
① This relationship can be established on the basis of theoretical or experimental research, and it can be represented in the form of algebraic equations, number tables, or graphs.
② When the change in input quantity is a function of time, one form of response characteristic is the transfer function.
Time response
A specified change in an input quantity causes a change in the output quantity over time.
Step response
The time response caused by a step change in an input quantity.
Slope response
The time response caused by the slope of an input variable changing from zero to a finite value.
Pulse response
The time response caused by applying a pulse function to an input.
Frequency response
In a linear system, the ratio of the Fourier transform of the output signal to the Fourier transform of the corresponding input signal.
Steady state
The characteristic parameters of the system remain in a constant state.
Note: For example, the characteristic parameters of a sine wave are the r.m.s value, frequency, and initial phase.
Transient
The state in which a variable rapidly transitions between two steady states.
Transfer function
A function that expresses the relationship between the input quantity and the corresponding output quantity within a specified range of conditions.
Gain gain
In a steady-state linear system, the ratio of the amplitude (or power) of the output signal to the amplitude (or power) of the corresponding input signal.
Attenuation attenuation
The reduction of signals in transmission systems.
Dead time delay
Also known as death.
The time from the moment when the input quantity changes to the moment when the output quantity of the instrument starts to change.
Damping
The dissipation of system energy during motion.
Periodic damping, underdamping
Also known as under damping.
The step response exhibits overshoot damping.
Aperiodic damping, over damping
Also known as over damping.
The step response does not exhibit overshoot damping.
Critical damping
A type of damping that falls between periodic damping and non periodic damping.
Note: Although overshoot occurs, it can still be considered as critical damping when it does not exceed a certain specified value (usually related to basic error).
Damping torque
The torque that stops the swinging of the movable part is in the opposite direction to the rotation direction of the movable part, and its magnitude is proportional to the rotational speed.
Damping torque coefficient
The movable part has a damping torque per unit angular velocity.
Damping factor
In the free oscillation of a second-order linear system, the ratio of the larger amplitude to the smaller amplitude of a pair of (opposite direction) continuous oscillations output near the final steady-state value.
Transient overshoot
The maximum transient deviation of the output beyond its final steady-state value during step response.
Time constant
In a first-order linear system caused by step or pulse inputs, the time required to complete 63.2% of the total rise or fall of the output.
Rise time
For step response, the time from the moment the output signal starting from zero reaches a specified small percentage (e.g. 10%) of the final steady-state value to the moment it first reaches a specified large percentage (e.g. 90%) of that steady-state value.
Setting time
The time from the step change of the input signal to the deviation of the output signal from the final steady-state value not exceeding the specified tolerance (e.g. 1%).
Note: Instruments with indicator devices, also known as damping time, establish time.
Step response time
When the input undergoes a step change, the time it takes for the output to reach the specified percentage of the difference between the final steady-state value and the initial steady-state value for the first time from the initial value.
Ramp response time
The time required from applying a ramp input to maintaining the output within the specified tolerance band of the input value multiplied by the static gain minus the first-order steady-state deviation value of the output.
Frequency response characteristic [Figure]
The graphical representation of logarithmic gain and phase angle as a function of frequency, usually expressed in logarithmic coordinates