In a manometer, the tube should contain a liquid whose specific gravity is ______ the specific gravity of the liquid whose pressure is to be measured.

Explanation:

U-tube Manometer:

(i) It consists of a glass tube in U shape, one end of which connected to the gauge point and another end open to the atmosphere.

(ii) The tube contains a liquid of specific gravity greater than that of the fluid of which the pressure is to be measured.

(iii) The choice of the manometric liquid depends on the range of pressure to be measured For the low-pressure range, liquid of lower SG is used and for the high range, generally, mercury is used.

(iv) A U-tube manometer is used inverted if the pressure differential is small (density of the manometric fluid is less than fluid) and A U-tube manometer is used upright if the pressure differential is large (density of the manometric fluid is large)

Limitation:

• This method requires reading of fluid level at two or more points since the change in pressure causes a rise in one limb and drop in another.