Explain the difference between accuracy, precision, and resolution in the context of process instrumentation.

Accuracy, precision, and resolution are three distinct but related concepts in the context of process instrumentation. Accuracy refers to how close a measurement is to the true value of the quantity being measured. A highly accurate instrument provides measurements that are close to the actual value, with minimal systematic error. Systematic error is a consistent error that always occurs in the same direction. For example, a temperature sensor that consistently reads 2 degrees Celsius higher than the actual temperature has a systematic error and is therefore inaccurate. Precision, on the other hand, refers to the repeatability of a measurement. A highly precise instrument provides measurements that are very close to each other, even if they are not necessarily close to the true value. Precision is related to random error, which is unpredictable and varies in both magnitude and direction. An instrument can be precise but inaccurate if it consistently provides the same incorrect reading. Resolution refers to the smallest change in the measured quantity that the instrument can detect and display. It is the fineness of the measurement scale. A high-resolution instrument can detect very small changes, while a low-resolution instrument can only detect larger changes. For instance, a digital thermometer with a resolution of 0.1 degrees Celsius can display temperature changes of 0.1 degrees or more, while a thermometer with a resolution of 1 degree Celsius can only display changes of 1 degree or more. It is possible for an instrument to have high resolution but low accuracy. In summary, accuracy is about how close the measurement is to the truth, precision is about how repeatable the measurement is, and resolution is about how small a change the instrument can detect.