Measurement Accuracy and Precision | Accuracy vs Precision in Sensor Measurement

eyc-tech Guide to Measurement Accuracy and Precision

What is Accuracy and Precision in Measurement?

In sensor and measurement instrument applications, accuracy and precision are two important indicators used to evaluate measurement performance. Many customers often ask questions such as “How is accuracy calculated?” or “What does instrument accuracy represent?” when selecting sensors or measurement devices. Therefore, understanding the concepts of measurement accuracy and precision is essential when choosing the appropriate measurement equipment.

Under normal operating conditions, the deviation between the measured result and the true value is referred to as measurement accuracy. The smaller the error, the higher the accuracy of the instrument. Measurement error is usually related to the instrument's measurement range.

Measurement Accuracy

In general, measurement accuracy can be expressed in two ways:

• Absolute Error: expressed as the difference between the measured value and the true value.
• Relative Error: expressed as the percentage of error relative to the measured value.

Absolute error indicates the difference between the measured value and the true value, while relative error represents the ratio of that error to the measured value, usually expressed as a percentage.

Accuracy vs Precision

Precision is a statistical concept that describes the degree of consistency among repeated measurement results. If multiple measurement results are very close to each other, the measurement system is considered to have high precision.

Conversely, if the measurement results vary significantly from one another, the measurement system has lower precision.

In quantitative analysis, the average of multiple measurements is often used as the final measurement result. However, without a reliable reference standard, systematic errors may be overlooked.

Therefore, measurement systems usually rely on reference standards established by international organizations, such as NIST – National Institute of Standards and Technology, to ensure traceability.

Systematic Error

Systematic error, also known as regular error, refers to an error that remains constant in magnitude and direction when the same physical quantity is measured repeatedly under identical conditions, or varies according to a predictable pattern when conditions change.

Systematic errors are typically caused by inaccurate instrument calibration, imperfect measurement methods, or environmental factors.

Another common type of error is random error, which may result from unpredictable environmental changes or random disturbances within the measurement system.

Although systematic and random errors cannot be completely eliminated, they can be significantly reduced through proper measurement design, calibration procedures, and quality control practices.

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