There are many indicators for instrumentation equipment. Understanding the main indicators of the instrument can help us better use and maintain instrumentation and improve production efficiency.
1. Accuracy and accuracy level
Accuracy refers to the degree of agreement between the measured result and the actual value, and is the maximum allowable value of the basic error of the meter. It is also customary to simply refer to the basic error or the allowable error. High precision means that systematic errors and random errors are small.
The accuracy level is the level at which the meter is divided according to the level of accuracy, which determines the error limit of the meter under standard conditions. The accuracy level of the meter is divided according to the reference error. If the maximum basic reference error of a meter is ±1.5%, the accuracy level of the meter is 1.5.
2. Hysteresis, dead zone and hysteresis
Hysteresis refers to a phenomenon characterized by a characteristic curve consisting of an increased rising section and a decreasing falling section.
A dead zone is a finite interval in which the change in input does not cause any appreciable change in output. The dead zone is expressed as a percentage of the input range.
The hysteresis (also called the variation) is the maximum difference between the two corresponding output values of the same input (if there is no other specification, the full range travel) when the input amount rises and falls. The hysteresis includes hysteresis and dead zone and is expressed as a percentage of the output range.
3. Repeatability error and reproducibility error
The repeatability error is the difference between the output values measured continuously in the same direction for the same input value under the same working condition. The percentage of the general dosage is expressed.
Reproducibility error is the maximum difference between output values that are repeatedly measured in two opposite directions of the same input value within a specified time under the same operating conditions. Reproducibility errors are comprehensive indicators including repeatability errors, hysteresis, dead zones, and drift, expressed as a percentage of the general range.
4. Sensitivity and sensitivity limits
Sensitivity is the degree to which the meter is sensitive to changes in the measured parameter. It refers to the ratio of the amount of change in the output signal to the amount of change in the measured parameter that causes the change in the output signal after the meter reaches a steady state. It is the slope on the meter's input and output conversion curves.
The sensitivity limit is the minimum amount of change in the input signal that can cause the meter output signal to change. In general, the meter's sensitivity limit should not be greater than half the absolute value of the meter's allowable error. The sensitivity limit is actually the dead zone.
5. Nonlinear error
For a meter with theoretical linearity, the degree to which the input-output characteristic curve deviates from the theoretical linear characteristic.
6. Dynamic error
Due to the component moment of inertia (time constant) present in the detection section, the error caused by the transmission hysteresis (pure lag time) is measured.
7. Time constant
The time constant is the time required for the output value of the meter to reach 63.2% of its stable value when a step signal is input.
8. Full travel time
The full travel time is the time required for the output to move from the lower limit to the upper limit or the reverse stroke when the input full scale step changes. Usually, 5% of the full scale is used as the output lower limit value, and 95% of the full amount is used as the output upper limit value.
9. Stabilization time
Settling time is the time between when the input signal jumps and when the output signal enters and no longer exceeds its final value specification (eg 5%).
10. Lag time
The lag time, also called time lag, is the time from the moment the input changes, to the moment it causes the output to begin to change.
11. Comprehensive error
Toal Probable Error (TPE) refers to the accuracy of the meter and the root mean square error of various additional errors such as static pressure and temperature.
12. Stability (degrees) and availability
Stability is the ability of the meter to remain constant over time under specified operating conditions. Usually measured by zero drift.
Availability is the ability of a meter to have or maintain a defined function at a time. It can be expressed by the following relationship: