This thesis documents the design details, development, and field testing of an advanced power system harmonic monitor. It begins by reviewing present harmonic standards and harmonic monitoring equipment. It then goes on to describe the design and field use of the first generation harmonic monitor. From the field use a number of problems with this monitor are identified leading to the second generation harmonic monitor known as CHART II. The acronym CHART means Continuous Harmonic Analysis in Real-Time. The design of the monitor including the data acquisition and computer processing equipment, as well as the display system, is such that it can acquire multiple channels of power system signals from remote locations. It can compute the harmonics of these signals continuously on a cycle-by-cycle basis, and store only the harmonics of interest. Harmonic computation is performed in real-time, with results displayed as they occur. Acquired data can be accurately time stamped for comparison with data from other monitoring sites, enabling simultaneous measurement at remote locations. The key areas of technology involved in implementing such an instrumentation system are: data acquisition from power system equipment, digital fibre optics, real-time digital signal processing, high speed multiprocessing bus systems, real-time multitasking operating systems, global positioning satellite systems, and computer networking. The application of digital signal processing to power system harmonic measurement is covered, and a field trial with the CHART II monitor is documented.