# Find the sensitivity and accuracy of electronic weighing scales?

1. Apr 3, 2005

### g33n13

How would I find the sensitivity and accuracy of electronic weighing scales?

2. Apr 3, 2005

### Integral

Staff Emeritus
Do a web search on the manufacturer and model number?

3. Apr 3, 2005

### SpaceTiger

Staff Emeritus
Take an object of known weight/mass and then weigh it with the scale N times. You can then get a mean and standard deviation of the weight measurements, Wi:

$$\bar W=\frac{\sum_{i=1}^{N}W_i}{N}$$

$$\sigma=\sqrt{\sum_{i=1}^{N}\frac{(W_i-\bar W)^2}{N-1}}$$

If I'm understanding what you mean by sensitivity and accuracy, then the sensitivity is the spread in the measurements, $$\sigma$$. To get the accuracy, you would have to perform the same experiment many times (let's say M times) with different weights and find the average value of the difference between the mean measurement and the actual value:

$$accuracy = \frac{\sum_{j=1}^{M}(\frac{\bar W_j-W_0}{W_0})}{M}$$

If this is supposed to be a simple experiment, you can ignore what I'm about to say.

These things will likely depend on many variables, so the results you get will depend upon the conditions in which you perform the experiment and the magnitudes of the weights you use. Really, what should be computed is the sensitivity and accuracy as a function of actual weight. Also, there's no reason to assume a priori that the distribution of errors will be gaussian, so the above should done via a bootstrap technique if more statistical rigor is required.