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Closed circuits have been used in electrical systems since Alessandro Volta's invention of the modern battery in 1800 made the first closed electrical circuits possible. Even though a capacitor in a circuit could be considered as an open circuit, its use requires electrical connections to a circuit. This paper reports successful measurement of fluid level using a self-resonating planar pattern of electrically conductive material that is an open-circuit single-component sans electrical connections that is wirelessly powered using external oscillating magnetic fields. The circuit responded with its own magnetic harmonic that changed monotonically with the fluid level. The same external antenna received the circuit response providing a means of interrogating the sensor. By eliminating electrical connections, there is no single point that, if damaged, prevents the circuit from being powered and interrogated, thus, eliminating a key failure mode of electrical devices. Sensors used for the initial fluid-level measurements have portions of their circuits severed from the other portions. The damaged sensors were then successfully used to measure the fluid level. Although the results for fluid-level measurement are presented herein, theoretically, many electrical devices whose functions depend on the use of electric fields, magnetic fields or resistance could be developed as open circuits. The applications are far-reaching, from safer damage-resilient self-sensing human-implanted medical sensors to applications with vehicle systems, buildings, food processing and storage, package tamper detection and other measurements that can be related to capacitance, inductance or resistance. Furthermore, this work lays the foundation for developing other electrical components that can be designed without the use of closed circuits or electrical connections.