Abstract: A metering device and method of modular construction allows ease of set up, maintenance and process changes, without the need for changing structures and/or custom parts and without the need for special tools. The metering device monitors various operating parameters with closed loop computer feedback to enhance piston and pump control for accurate metering, to predict when routine maintenance should be performed to avoid failure, to permit automatic fine tuning of displacement during operation and to enhance production within specification tolerances while minimizing downtime. The piston cylinder assembly within the hard tooling can be readily changed to selectively have different diameter cylinders and pistons and to be readily convertible between macro and micro liquid metering. The metering device with its controls and ease of component changes allows metering systems with multiple metering devices to be easily set up with improved synchronization and accurate mixing ratios.