Emerson Exchange 365

1. There could be a couple deciding factors - magmeter size will commonly be selected to match the process piping size to avoid making piping changes; select a size that provides a good velocity range for the application's flow range - it's good practice to try to keep the minimum flow rate above 2 ft/sec velocity to maintain the best accuracy, velocities are usually kept below 20 ft/sec to minimize wear on piping and other devices, for abrasive applications such as slurries the upper velocity should be limited to under 10-15 ft/sec depending on the severity of the abrasive factors of the slurry.
2. This is dependent on the available power, it doesn't make a difference in the operation or performance of the magmeter.