Calibration of a Flow Meter

Greetings new engineer. Congratulations on your new position at Flow Solutions. The following is a tutorial to prepare you for your role calibrating flow meters. Please go through this guide carefully and feel free to reference it as you become more familiar calibrating on your own.

After following the procedure from the hydraulic flow meter experiment, in this case you will be using data from the venturi flow meter, you will have a set of data for the manometer deflection and the corresponding Flow rate. Using the industry standard excel software and the provided sheet with the necessary calculations and properties, insert the data obtained and create a plot of Flow rate vs. Manometer deflection, and after plotting the data, fit a power trendline to the data to obtain a calibration curve. This will be the linear plot of the data. Next, create a copy of the plot and adjust the scale of the x and y axes to be logarithmic. Fit a new trendline to obtain another calibration curve, this time it should appear more linear

The provided excel sheet will calculate the discharge coefficient and Reynold's number from the data. Create a new plot with discharge coefficient plotted vs Reynold's number. Make the x-axis a logarithmic scale and leave the y-axis as linear to create a log-linear plot. From the plot, observations can be made regarding the discharge coefficient. Observe that the data from the example test varies greatly and does not have a clear linear relationship at low and high discharge rates. Additionally, a discharge rate of 1 is ideal but this is not achieved in the data recorded. This is due to the calculations not taking into account more complicated fluid dynamic properties such as turbulent flow, and frictional forces from the pipe wall. It is possible to minimize these sources of error by using a much slower flow rate but this is not viable with the current sensitivity of the flow meter being tested.

Now that we have a calibration curve for the venturi flowmeter, the next step will be to find a calibration curve for the paddlewheel flow meter. Similar to the venturi flow meter calibration, used the data acquired from the experiment and create a plot of the voltage output from the paddle wheel vs. the flow rate at which the voltage was measured with a linear scale on both axes. Fit a linear trend line after plotting the data to obtain the calibration curve for the paddlewheel flow meter. In the sample data used in this tutorial, observe how linear the data is and how it clearly indicates a rising flow rate. The linearity of the data indicates that the paddlewheel flow meter is relatively precise for the range of flow rates used in the test and accurate enough for the application. If we were to raise the flow rate much higher we could expect to see a declining and cutoff flow rate as the paddlewheel reached a maximum flow rate at which it could take accurate measurements. The rising flow rate velocity and maximum velocity can be obtained from the provided datasheet and from the sample data it is 0.0078 m/s and 0.02353 m/s respectively.