Advanced pH Measurement and Control: Digital Twin Synergy and Advances in Technology details system design, installation, maintenance and ongoing improvement, including a special focus on how digital twins and first-principles charge balance contribute to innovation, operability, productivity, reliability and maintainability. It offers insights into key principles and advances in electrode technology and diagnostics, including a simple and largely untapped method for computing titration curves that match laboratory curves, as well as guidance on selecting and implementing the best control valves and strategies. The extraordinary sensitivity and rangeability of pH used for measuring and controlling hydrogen concentration introduce many challenges in managing the nonlinearity in the control loop and the precision needed for the control valve. This, combined with pH's critical role in maintaining cell health in biological processes, as well as in the production of clean water, food, pharmaceuticals and chemicals, makes the best pH control system particularly important and challenging. Despite these challenges, the outcomes can lead to significant reductions in equipment costs and, more importantly, substantial improvements in system reliability and performance. Finally, the appendices cover fundamental principles and provide guidance on using new PID features to reduce project costs and maximize process efficiency, capacity and safety.