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# Uncertainty in Graph Watch

1. I've plotted a graph of resistance vs temperature and this is it: <br />
<br />
I have then enlarged a portion of the graph to find a certain temperature change at a two specific resistances: <br />
<br />
The faded vertical lines indicate the change in temperature. <br />
<br />
My question is, I've used a thermometer (+/- 1 degree uncertainty) but the temperature change is 0.32*C so how would I find the uncertainty in that? (My scalar uncertainty is greater than the value itself)
2. (Original post by munchen102)
I've plotted a graph of resistance vs temperature and this is it: <br />
<br />
I have then enlarged a portion of the graph to find a certain temperature change at a two specific resistances: <br />
<br />
The faded vertical lines indicate the change in temperature. <br />
<br />
My question is, I've used a thermometer (+/- 1 degree uncertainty) but the temperature change is 0.32*C so how would I find the uncertainty in that? (My scalar uncertainty is greater than the value itself)
How did you measure a change of less than a degree with a thermometer that is only accurate to one degree?
The uncertainty applies to the reading, not to the delta.
3. (Original post by joostan)
How did you measure a change of less than a degree with a thermometer that is only accurate to one degree?
The uncertainty applies to the reading, not to the delta.
I didn't. I took several readings at 0,5,10,20,30 up to 90*C and then plotted a graph of resistance vs temp. I then used this graph (graph1) to measure the small temperature change at a certain change in resistance.

So the ΔT wouldn't have an uncertainty?
4. (Original post by munchen102)
I didn't. I took several readings at 0,5,10,20,30 up to 90*C and then plotted a graph of resistance vs temp. I then used this graph (graph1) to measure the small temperature change at a certain change in resistance.

So the ΔT wouldn't have an uncertainty?
The uncertainty applies to the measured values, e.g. 0, 5, 10, 20 etc. It does not apply to ΔT, in so many words, it applies to the points at either end, but not the ΔT itself.
5. (Original post by joostan)
The uncertainty applies to the measured values, e.g. 0, 5, 10, 20 etc. It does not apply to ΔT, in so many words, it applies to the points at either end, but not the ΔT itself.
Thanks I understand that. So is there any uncertainty in the value taken from the graph?
6. (Original post by munchen102)
Thanks I understand that. So is there any uncertainty in the value taken from the graph?
In the ΔT? Yes but it's complicated to work out and probably not required for whatever it is you're doing.
7. (Original post by joostan)
In the ΔT? Yes but it's complicated to work out and probably not required for whatever it is you're doing.
Thank you much appreciated.

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Updated: April 12, 2013
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