Why Manometer is used in Mine?
A manometer, commonly known as water gauge in a mine, is used to measure the pressure difference in the range of above 25 Kgf/m2. It consists of a U-shaped glass tube of uniform bore(about 6.5mm of internal diameter, tubes of smaller bore may give erroneous results due to capillary action).The upper ends of both the limbs are bent to horizontal so that rubber tubes can be easily connected to them. Each limb of the u-tube is about 50cm long (the exact length, of course, depends on the pressure range to be measured), and the limbs are about 20mm apart. A scale graduated in mm divisions is mounted vertically between the limbs. Water is used as manometric fluid—- hence the name water gauge. The other liquids that can be used in a manometer are: alcohol, mercury, glycerin——the liquid to be used depends on the pressure range to be measured.
To measure pressure difference between two places, the open ends of two rubber tubes connected to two limbs of a manometer are placed at these two places with the rubber tubes facing the air current. The difference in the water levels in the two limbs of the manometer gives the pressure difference. 1-mm w.g. i.e. 1 mm difference in the water level equals a pressure of 1 kgf/m2. The scale between the limbs indicates the water level difference in mm.
