The dial runs from 0 mmHg up to about 300 mmHg.
You shouldnâ€™t need numbers much past 200, as even systolic pressures over 180 constitute an emergency.
When you look at the dial, make sure it is at the zero baselines before starting.
If it isnâ€™t, you need to calibrate it using a mercury manometer.
Connect it with a Y connector, and once you move the dial over, check the pressure at several readings on both meters to make sure the aneroid manometer matches the mercury manometer.