Calibrating Flowmeter

In order to calibrate the facility's flowmeter, the following steps need to be taken:

To begin, the mercury-water manometer level must be zero. You can adjust the levels by slowly opening and closing the "CAL VALVE" drain valves (red valves at the top) to eject excess air and level the liquids. If need be, adjust the scale to give a reading of 0. This will esnure the discharge valve is 0.

Use the bottom left reading of the monitor to ensure the voltage is zero-ed out. This reading is for the Validyne differential pressure transducer. With the discharge valve closed, slowly open the manometer valves (found on the Venturi flowmeter) and obtain readings of the transducer output and manometer lines. Five sets of data should be taken.

In the experimental data above, your results should look similar to the top left and top right graphs. The left is linear, while the right is logarithmic. In this case, the logarithmic graph has errors in data collection because the set of data should be a straight line to indicate the relationship between flow rate and manometer deflection. IF your logarithmic graph is shown to be linear, your calibration steps are good so far.

Ensure the Gain Adjust control of the paddlewheel flowmeter is set to the following:

P1: 6.25 turns, P4: 6.25 turns, P3: 3.00 turns

Slowly open the discharge valve until acceptable manometer deflection is reached or the valve is fully open. Record the Validyne pressure differential voltage reading and Signet paddlewheel reading voltage at the instant when the Signet reading is non-zero. Take a weight-time measurement at the maximum flow rate. Observe the deflections at slower flow rates.

Observe the following experimental data. You can calculate Reynold's number by dividing the flow rate by the viscosity and plot that as the input of a function of the discharge coefficient (seen in the bottom left graph). You can also analyze the paddlewheel flowmeter's calibration curve.

For this set of data, not all graphs agree with the theoretical values. Reynold's number graph should have a constant rise of data points due to the logarithmic nature of the graph. The other graphs show mostly correct representations of data. For finding the discharge coefficient, accurate weight-time measurements must be recorded and voltage measurements should be made by finding the average of the alternating values from the monitor.

The paddlewheel measurements are accurate, due to the consistency of slop between the points.