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# Pressure Sensor Accuracy Affected by 3 Specifications

The accuracy of a pressure sensor affected by three specifications: error, precision, and uncertainty. In actual work, it is easy to confuse or misuse the three. This article will start with the definition, elaborating the connection and difference between the three.

Ⅰ. Definition of the three
1. Not just for the pressure sensor. In theory, the measurement error refers to the measurement result minus the measured true value, which is the difference between the measurement result and the measured true value. The so-called true value refers to the true pressure of the quantity itself when measuring a quantity. The true value of the measurement is an ideal concept and is generally unknown. For the purpose of use, the measured value with a high-level accuracy standard is called the actual value in the actual measurement, and the actual value is used instead of the true value. In some specific cases, the true value is known. For example, a full circle has a circumferential angle of 360°, and the three internal angles of the triangle are 180°,the value of the international kilogram reference according to the definition can be considered to be 1kg,and many more.
2. Measurement precision refers to the degree of agreement between the measurement result and the measured true value. Since we can’t get the exact true value in many cases, the precision is defined as the closeness between the measurement result and the measured true value. It is a qualitative concept that cannot be operated as a quantity, which means: The precision is high or low, the precision is level 0.2, the precision is level 3, and the precision is in accordance with the XX standard. All of them refer to meet the requirements of the technical indicators (a certain level) or the requirements of a technical specification.
3. Measurement uncertainty is a parameter associated with the measurement result, which reasonably characterizes the dispersion of the measured value. It represents the dispersion of the measured value, expressed as an interval, that is, the interval in which the measured value may be distributed. According to its acquisition method, we can divide it into two categories: A and B. Class A assessment component is the uncertainty assessment made by statistical analysis of observation columns. Class B assessment components are estimated based on experience or insight and assume that there is an uncertainty component characterized by an approximate standard deviation.
We can see that there is still a close connection between error, precision and uncertainty. The concept of uncertainty is the application and extension of error theory, and error analysis is the theoretical basis of uncertainty evaluation. In the estimation of the B component, it is inseparable from the error analysis. Most of the uncertainty of measurement is a technical indicator of the measuring instrument, which indicates the responsiveness of the measurement result to the true value.

II. Reasons for the three
The measurement error, precision, and uncertainty are different in the following aspects.
1. The measurement error caused by defect in the measurement process and these defects are caused by a variety of reasons, including errors generated by measurement devices, errors caused by environmental conditions, errors generated by measurement methods, errors generated by personnel, etc. We usually classify it into systematic error, random error and coarse error.
2. Measurement precision is the result of system error, such as the error produced by the measurement device, which determines the accuracy of the measurement results.
3. The cause of the uncertainty is related to the measurement principle, measurement instruments, measurement environmental conditions, measurement procedures, measurement personnel, and data processing methods. In addition, it is related to the assessor’s experience, range and level of knowledge. It consists of multiple components, some of which can be estimated by the statistical distribution of the measurement and be characterized by experimental standard deviations. Other components can be estimated by using a hypothetical probability distribution based on experiment or other information, or characterized by standard deviation.

III. Influencing factors of the three
1. The measurement error is objective and not affected by external factors, and does not change with the degree of human cognition. Any measurement has its imperfections, so there will be some errors at any time.
2. Measurement uncertainty obtained by people through analysis and evaluation, so it is related to people's understanding of the measured quantity, impacted quantity and measurement process.
3. The measurement precision is related to the accuracy and level of the instrument used in the measurement process. The higher the accuracy, the closer the measurement result is to the true value.
IV. Assessment purposes of the three
1. The measurement error is the difference between the measurement result and the true value, the purpose is to indicate the degree to which the measurement deviates from the true value. It is a quantitative concept that shows the specific deviation.
2. Measurement precision is the degree of agreement between the measurement result and the measurement true value. It is a qualitative concept that indicates whether the measurement result are within the standard requirement.
3. Measurement uncertainty is an estimate for the dispersion which resulting error in order to indicate the dispersion of the measured value, indicating that the measurement result is within a certain interval.
V. Assessment results of the three
1. The measurement error is a specific magnitude with positive and negative sign, which obtained in each measurement. It can only obtained by measurement, which is a point on the number axis.
2. The measurement uncertainty expressed as an interval on the number axis, that is, the range in which the measured value may be distributed. It is an unsigned parameter expressed as a multiple of the standard deviation or standard deviation or a half-width of the confidence interval. People assess it based on experimental data, experience and other information, and can be quantitatively determined by A and B assessment methods.
3. Measurement precision is for the accuracy of the measurement equipment, which is not a quantity, and is impossible to operate as a quantity.

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