Uncertainty in Measurements: Understanding Multiplication Factors

AI Thread Summary
Understanding how to calculate uncertainty in measurements involves knowing when to apply multiplication factors based on accuracy specifications. For example, when using a digital voltmeter with a specified accuracy of ±1% and an additional uncertainty of ±10mV, the reading of 4.072V should be recorded as 4.072 ± 0.051V after calculating the total uncertainty. This total is derived from 1% of the reading plus the additional uncertainty, which is then rounded appropriately. Rounding should be based on the significant figures or decimal places of the data, following the reporting conventions of the organization. Clear guidelines for reporting uncertainty help ensure accurate communication of measurement confidence.
averycasille
Gold Member
Messages
9
Reaction score
0
Hello, guys! (And girls, but.. you know..)
There are several things I do not quite understand, so, can you help me clear my doubts? ^^

1) How do I know when to multiply the value of calculated data when it comes to determining the uncertainty of the data?

2) When do I multiply the percentage of accuracy with given data when determining uncertainty?
 
Physics news on Phys.org
I have no idea what you are asking, Perhaps you could give an example of your issue.
 
Sorry for being unclear!
• The manufacturers of a digital voltmeter give, as its specification, accuracy +-1% with an additional uncertainty of +-10mV. The meter reads 4.072V. How should this reading be recorded, together with its uncertainty?
 
averycasille said:
How should this reading be recorded, together with its uncertainty?

You record the reading as is 4.072 V. The uncertainty should be 1% of that reading + 10 mV.= 0.0407 V + .01 V = .0.0417 V =0.042 V ( rounding )
 
Ohh. So, when the specific accuracy is given, I should always multiply with the data and add it with the additional uncertainty? Is that it?
Also, regarding the rounding off, that should be based on significant figures/decimal place of the data? O.O
 
averycasille said:
so, regarding the rounding off, that should be based on significant figures/decimal place of the data? O.O[/QUOTE

yes
 
gleem said:
You record the reading as is 4.072 V. The uncertainty should be 1% of that reading + 10 mV.= 0.0407 V + .01 V = .0.0417 V =0.042 V ( rounding )
0.0407V + 0.010 V = 0.0507V which is 0.051 after rounding to an appropriate precision.
 
Thanks, peeps! But, significant figure OR decimal place? Sorry for asking a lot [emoji848][emoji23][emoji24]
 
As a general rule, significant figures are not appropriate in the real world. They are a toy for the classroom. The reporting conventions for your organization should be followed. One recommendation from http://web.mit.edu/fluids-modules/www/exper_techniques/1.Recording.Uncertainty.pdf is:

"As described above, to determine a quantity x, we make a measurement, report our best estimate, and report the range over which we are reasonably confidant the actual value lies: (measured value of x) = xbest ± δx ."

e.g. 4.072 ± .051 V
 
  • Like
Likes jk494
  • #10
Thanks for the assistance, everyone. Means a lot [emoji120] Really appreciate it!
 
Back
Top