Calculates the uncertainty in observed volume, mass, standard volume and energy flowrate for a gas USM. USM flowrate uncertainties are determined from an assessment of the meter calibration performance, installation and on-going performance/usage parameters. Density, standard density and CV calculations and their uncertainties are performed using user-selectable calculations. Pressure and temperature uncertainties are determined using the technical specification for the transmitters selected from the integrated transmitter selection tool.
The General tab is used to enter information, which is saved along with the uncertainty calculation and included in reports which are generated.
The tabs used for inputting data and calculating the uncertainty in the individual components of the uncertainty can be seen along the top of the module window.
The report tab is only visible once the calculation has been run and will not be visible if any parameters are changed until the calculation has been run once more.
The options section controls how the calculation is performed and dictates which inputs are required.
This relates to all pressure value units in the module, with the exception of the Atmospheric Pressure which is always bar (absolute).
Note: As described above, if Absolute is selected inputs are required for Absolute and Atmospheric pressure and if Gauge is selected inputs are required for Gauge and Atmospheric pressure.
The default value for Atmospheric Pressure is set to 1 standard atmosphere (1.01325 bar)
By default, the module will calculate the uncertainty for a single metering stream. If parallel streams are selected the Station Uncertainty will be calculated assuming the metering streams are nominally identical and the flow is split equally between the streams in use.
Note: When selecting parallel streams the correlation between inputs has to be considered and the user is presented with a further option to control how the correlation is defined.
This is the line pressure of the gas stream. As described above, if Absolute is selected inputs are required for Absolute and Atmospheric pressure and if Gauge is selected inputs are required for Gauge and Atmospheric pressure.
Number of parallel meters
This input is only visible when parallel streams are selected for the station uncertainty and refers to the number of in-use metering streams the flow is divided between.
This is the measured temperature of the gas stream.
The velocity of gas flowing through the USM.
Note: Ultrasonic meters operate over a specified velocity range, which is independent of temperature, pressure, or composition.
The outputs section shows the calculated flow rate and uncertainty taken from the Flow Rate tab.
The following blocks are used within this uncertainty module: