A manometer is a device used to measure pressure: that is, the physical quantity that reflects the force exerted by a body on a unit of surface. With these instruments it is possible to check the pressure of a gas or a liquid.
Many manometers are usually responsible for recording the gauge pressure, which is the difference between the actual pressure and the atmospheric pressure. For this they take the atmospheric pressure as a reference and then determine the difference with the real pressure of the fluid. It should be noted that atmospheric pressure is the pressure exerted by the atmosphere on the bodies that are immersed in it: at sea level, its normal value is 1013 mbar or 760 mm Hg.
There are two main types of pressure gauges. The analog gauges exhibit the pressure measured by a needle, while the digital gauges have an LCD screen which presents the result.
Pressure gauges are used, for example, to measure the pressure of vehicle tires. Controlling this pressure is very important: the tires must have the pressure suggested by the manufacturer to ensure their adherence to the pavement, avoid excessive wear and not encourage excessive fuel consumption. Since the tires lose pressure little by little but constantly, it is essential to use a pressure gauge to perform the check periodically.
To measure blood pressure, meanwhile, a blood pressure monitor or sphygmomanometer is used. It is an element that has a pressure gauge, a stethoscope and an inflatable cuff and is used to record diastolic pressure and systolic pressure.