The continued adoption of renewable energy and distributed generators has resulted in a rising number of supply points within the traditional electric power grid, necessitating the need for enhanced monitoring capabilities. The IEC 61850 standard can become an enabling technology for enhanced monitoring, but prohibitively high costs and complexity of compliant devices could become an impediment. Open-source IEC 61850 libraries, coupled with single-board computers and digital signal processors, provide a possible low-cost solution. This work presents the process of modelling and implementing such a device using an IEC 61850 open-source library, a Raspberry Pi embedded platform and an ADE9000 analogue front-end. Measurement accuracy and interoperability compliance tests are conducted to determine the suitability of the device for use in an industrial setting. A key contribution of the findings in this paper is the modelling and implementation of a viable, interoperable and low-cost IEC 61850-based power quality monitoring device using off-the-shelf components and an open-source software library. The implementation of this device provides a platform that is easily modifiable for use in a range of applications. Another contribution is the method of modelling IEC 61850 logical nodes and functions to analogue front-end measurement registers. The knowledge demonstrated shows how device modelling techniques can be used to extract additional information for mapping to existing logical nodes or to develop new ones. The paper's findings result in a low-cost IEC 61850-based power quality monitoring device. The device has applications as a general utility-scale monitor for DER plants, check metering, IEC 61850-based power quality mitigation algorithms and short-term power quality studies. It may also function as a low-cost entry point to IEC 61850-based communications in smaller municipalities, and additionally as a lab test and prototyping tool for technicians, engineers and university students.