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# Uncertainty in volume measurement

## Uncertainty in volume measurement

(OP)
I would like to know how the uncertainty of a measured volume might differ between two measurement methods. In each case the flow rate of water into a collection tank is measure with turbine flow meters with stated accuracy of +/- 1% of flow rate. For the sake of discussion it is assumed that there is no error in the collection time measurement used to determine volume from the indicated flow rate, and that the flow is steady.

In the first case, a single flow meter is used to measure the flow rate into the tank. Volume is determined by multiplying collection time by the instantaneous flow rate.

In the second case, the same flow is divided into three pipes, each with a turbine flow meter measuring flow rate into collection tank. Volume is determined by summing the three flow rates and multiplying by collection time.

Would there be any difference in the uncertainty in measured volume between the two methods? How would uncertainty be calculated for each case?

### RE: Uncertainty in volume measurement

That does sound like a homework question. If you make the ridiculous assumption that the errors in the three gages are independent, then without doing the maths that you sre supposed to be handing in, I'd guess the error is reduced by the square root of three.

Cheers

Greg Locock

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