Flow measurement in partially filled pipes presents greater complexity compared to fully filled systems, primarily due to the complex velocity distribution within the cross-section, which is a key source of measurement inaccuracy. To address this challenge, an ultrasonic flow meter was designed and developed, capable of simultaneously measuring both flow velocity and fluid level. To improve measurement accuracy, a flow profile correction factor (FPCF) was derived based on the velocity distribution characteristics and applied to the raw flow meter output. A dedicated open-channel flow loop incorporating a 250 mm diameter pipe was constructed to test and calibrate the system under controlled conditions. Flow rates in the loop varied from 2 to 6 liters per second. The accuracy of the flow meter was evaluated using the Flow-Weighted Mean Error (FWME) metric. Experimental results showed that applying the FPCF significantly improved accuracy, reducing the maximum flow measurement error from 8.51% to 2.44%. Furthermore, calibration led to a substantial decrease in FWME from 1.78% to 0.08%, confirming the effectiveness of the proposed methodology. The flow meter was also subjected to clogging scenarios by artificially obstructing the flow. Under these conditions, the device was able to reliably measure the flow and successfully detected the clogging, triggering an alarm to the operator to take necessary action.