Davidson Measurement Tech Tips

Resolution or Accuracy?

A common misunderstanding that we come across is the difference between resolution and accuracy, this tech tip is provided to help clarify the characteristics.

When we discuss applications two questions always arise: "What resolution do you need?" and "to what accuracy do you want the measurements?"

In many instances the reply is "aren't they the same?" The answer is no. For the sake of definition we provide the following: Resolution: the minimum change that can be detected in the process. Accuracy: the difference between the signal value at that measured point compared to the true value.

When you are determining the sensor to use in the application, then the resolution must be a smaller figure than the accuracy. As an example, a displacement application requires a sensor that has a full-scale value of 1000mm to an accuracy of 0.1% full-scale, or 1mm, the resolution (the minimum change to be detected) is 0.05mm. You receive two data sheets on different transducers, their specifications are:

Transducer "A": range 1000mm, accuracy 0.1% FS, resolution 0.005%

Transducer "B'": range 1000mm accuracy 0.005% FS, resolution 0.05%

Evaluating the transducers highlights the difficulty with transducer "B".

Even though transducer 'B' has a better accuracy, its resolution does not meet the required specifications, thus it cannot be used. In fact, a transducer specified in the manner of transducer 'B' is somewhat misleading as it's calibration could not be achieved, given that the minimum change in output is worse than the claimed accuracy!

Resolution can be specified in many forms, so please be careful when evaluating specifications. Should you have any questions or need further clarification, just contact us and we will be happy to help.