I am working with a 6-axis force-torque sensor to measure the thrust and moments of a model jet engine. I want to understand the significance of the accuracy (measurement uncertainty) and precision (resolution) of these sensors. Note: I understand the textbook definitions well, I want to understand how these translate to real-world applications.

A realistic sample problem is as follows:
There are 2 sensors in the market.
Say both have the Maximum calibration for Fz as 1000N.
Both have the maximum measurement uncertainty of 1% of the Full-Scale calibration.
And say the first one has a resolution capacity of 0.1N and the second one has a resolution of 0.2N.

Here is what I understand:
The results of measurements will be accurate within 1% of 1000N which is $\pm$10N.
The resolution of the measured value for the first sensor is 0.1N and for the second 0.2N.
So if the measured thrust is 100.4N then I should report my measurement as 100.4N $\pm$10N.

The questions:
What is the significance of resolution here? Since accuracy is 10N which is more than resolution isn't resolution insignificant here?
Both force sensors seem to be giving almost the same information. Both the first and second sensors say my value will be something within the range of 90.4N to 110.4N. How does resolution come into play here?
A better resolution than accuracy seems to be useless.

Does resolution come into play when talking about repeatability? For eg: When I do the measurement again the first sensor is expected to give me a value of 100.4N $\pm$ 0.1N whereas, the second sensor is expected to give a value of 100.4N $\pm$ 0.2N?

Please provide me with an explanation on the same. Thanks!


1 Answer 1


The resolution is in effect the smallest scale division that you can use to take a reading.
Resolution comes into play if you are looking for changes in a reading rather than the absolute value relative to a standard (accuracy).

So with your jet engine it might be important for you to see if the thrust changes with time without knowing exactly (relative to a standard) how much the change is.

So you might get a set of readings like $100.4,\,100.2, 99.6$ and $99.1$.
From this data you know that there has been a continual decrease in the readings and that those changes are real to within say $\pm$ one scale division.
Given that the calibration accuracy is fairly high at $\pm 1 \%$ it is likely/possible that the changes are accurate to the resolution of the scale.


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