We present an extended study for upgrading a classical rotameter, a volume flow measuring device, by integration of wirelessly powered in-flow sensors. Therein, we used inductive power transfer operating at 13.56 MHz based on multiple transmitter coils distributed along a tube of the rotameter. The receiver coil was wound on the float being displaced along the pipe depending on the flow. A second coil on the float served for position detection, allowing, on the one hand, to identify and power just the two transmitter coils in direct vicinity of the float and, on the other hand, replace the visual readout of classical rotameters by a digital signal.We show comprehensive simulations of the transferred energy with many different coil arrangements and transmitter–receiver combinations, and normalized the results to allow for a generalized analysis. To verify our simulations, we demonstrated our approach on a 1-inch pipe, with transmitter coils of 34 mm diameter at a distance of 20 mm to each other, and a receiver coil with a diameter ranging from 11 mm to 23 mm. The system achieved a stable power transfer with less than 5% coupling factor variation regardless of the float position, delivering a steady 3.3 V output. The position detection using the second coil of the float enabled an average positioning tracking accuracy of 0.44 mm. We demonstrate the system’s functionality by powering a temperature sensor, and a Bluetooth transmitter, all embedded in the float, i.e., inside the pipe, maintaining stable operation with a standard deviation of only 381 mV in the received voltage across the entire travel range.Eventually, the system was evaluated on an industrial test rig equipped with external flow and temperature sensors showing good agreement between the embedded and external sensors.
