The feeders for powders and granules with the accuracy range of 1% to 5 % of set range depending on material feed are classified as volumetric feeders. There are dozen types of volumetric feeders available. They operate on the principal of feed rate control by volume instead of weight. Advantages of volumetric feeders include low initial cost, good overall performance at low feed rates and acceptable accuracy for materials with stable density and uniformity. Some of the volumetric feeders are roll feeder, screw feeder, belt feeders, paddle feeders and vibrating feeders.
The objective of using volumetric gas flowmeter is to measure the flow of gas. It uses discrete differential pressure, absolute pressure, and temperature sensor measurements to determine gas flow. Displays for flow meters can be simple analog indicators, and numeric or alphanumeric digital readouts.