# How to write uncertainities on different measurement

1. Jun 10, 2009

### Awsom Guy

I need some advice on how to write uncertainities on different measurements.
I need this urgently.
Thanks

2. Jun 10, 2009

### fatra2

Re: Uncertainties

with a delta $$x \pm \Delta x$$

3. Jun 11, 2009

### Awsom Guy

Re: Uncertainties

i mean on measurements

4. Jun 11, 2009

### Nick89

Re: Uncertainties

$$x = (3.01 \pm 0.01) \text{ cm}$$

You mean like that? Otherwise, your question is so vague and general, I have no idea what you want.

5. Jun 11, 2009

### Awsom Guy

Re: Uncertainties

That is it exactly what I want.

6. Jun 11, 2009

### Nick89

Re: Uncertainties

You simply write down the result of your measurement, and then you decide what the uncertainty is. You round the uncertainty to one significant digit (0.0193 becomes 0.02) and you round the measurement result to the same amount of digits (as long as they are in the same units). You then write it down as
$$y = (x \pm \Delta x) \text{ [unit]}$$
where x is the measurement result and delta x the uncertainty.

7. Jun 11, 2009

### Awsom Guy

Re: Uncertainties

Well my question was about the measurements in a ruler in mm and a protractor.
I guess it would be +/-1 degree and +/- 0.5mm.

8. Jun 15, 2009

### fatra2

Re: Uncertainties

Hi there,

I believe I can help you with this one. The uncertainty of an analogue equipment is half the smallest measurement possible (0.5mm for your ruler). The uncertainty of a digital device is the smallest measurement possible (1mm for digital ruler that measures in mm).

Cheers