Page 49: of Offshore Engineer Magazine (Nov/Dec 2014)

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Production

NEL’s fow measurement facilities, at East Kilbride, Glasgow. understanding of how the measurement make an estimate of the magnitude of the advantages, for example, it shows the system works. uncertainty. distribution in the output which can be 4. Assign a probability distribution to used to view whether the distribution

The Monte Carlo method each of the uncertainty sources. is skewed or rectangular in shape. This

The Monte Carlo method is an alternative 5. Use a random number generator to technique is also particularly useful way to estimate measurement uncertain- assign a “measured value” for each input when the uncertainties are large com- ties and is described in supplement 1 to variable based on its uncertainty value pared with the measured values.

GUM. and probability distribution. It has been shown that the combined

The method also involves a series of 6. Calculate the fnal result using the use of the Analytical and Monte Carlo steps: “measured values” as inputs. methods can be useful. The advantages 1. Defne the relationship between all the This process is repeated many times, of carrying out both methods on the same inputs to the measurement and the fnal until there is enough data to analyze the system are: • result. output distribution. The uncertainty in The two methods can be used to cross 2. For each input, draw up a list of all the the fnal result can then be estimated by check against each other.

• factors that contribute to the uncertainty calculating the standard deviation of the The Monte Carlo method can be used in that input. output data. to show if the output distribution is 3. For each of the uncertainty sources The Monte Carlo method has some skewed or rectangular. It can also be oedigital.com November 2014 | OE 51 050_OE1014_ProdOps1_NEL.indd 51 10/21/14 5:27 PM