Based on a principle developed by Evangelista Torricelli in 1643, theMercurial Barometeris an instrument used for measuring the change in atmospheric pressure. It uses a long glass tube, open at one end and closed at the other. Air pressure is measured by observing the height of the column of mercury in the tube. At sea level, air pressure will push on the mercury at the open end and support a column of mercury about 30 inches high. If you usedwaterinstead of mercury, you would need a glass tube over 30 feet in length.As atmospheric pressure increases, the mercury is forced from the reservoir by the increasing air pressure and the column of mercury rises; when the atmospheric pressure decreases, the mercury flows back into the reservoir and the column of mercury is lowered.

An aneroid barometer is an instrument for measuring pressure as a method that does not involve liquid. Invented in 1844 by French scientist Lucien Vidi[11] uses a small, flexible metal box called an aneroid cell (capsule), which is made from an alloy of beryllium and copper. The evacuated capsule (or usually more capsules) is prevented from collapsing by a strong spring. Small changes in external air pressure cause the cell to expand or contract. This expansion and contraction drives mechanical levers such that the tiny movements of the capsule are amplified and displayed on the face of the aneroid barometer. Many models include a manually set needle which is used to mark the current measurement so a change can be seen. In addition, the mechanism is made deliberately "stiff" so that tapping the barometer reveals whether the pressure is rising or falling as the pointer moves. This type of barometer is common in homes and in recreational boats but also used in meteorology, mostly as barograph and pressure instruments in radiosondes.

Motometer (historical names: Moto Meter, MotoMeter, Moto-Meter, MM) is a brand, known for measuring and displaying instruments for workshops and vehicle equipment. The originally independent company was founded at the beginning of the 20th century in the area of Stuttgart (South Germany). Until its insolvency in 1995, the Moto Meter AG was listed on the Frankfurt Stock Exchange.[1]

Blood pressure(BP), sometimes referred to asarterial blood pressure, is thepressureexerted by circulatingbloodupon the walls ofblood vessels, and is one of the principalvital signs. When used without further specification, "blood pressure" usually refers to thearterialpressure of thesystemic circulation. During each heartbeat, blood pressure varies between a maximum (systolic) and a minimum (diastolic) pressure.[1]The blood pressure in the circulation is principally due to the pumping action of the heart.[2]Differences in mean blood pressure are responsible for blood flow from one location to another in the circulation. The rate of mean blood flow depends on the resistance to flow presented by the blood vessels. Mean blood pressure decreases as thecirculating bloodmoves away from theheartthrough arteries andcapillariesdue toviscouslosses of energy. Mean blood pressure drops over the whole circulation, although most of the fall occurs along the small arteries andarterioles.[3]Gravity affects blood pressure viahydrostaticforces (e.g., during standing), and valves in veins,breathing, and pumping from contraction of skeletal muscles also influence blood pressure in veins.[2]Blood pressurewithout further specification usually refers to the systemic arterial pressure measured at a person'supper armand is a measure of the pressure in thebrachial artery, the major artery in the upper arm. A persons blood pressure is usually expressed in terms of the systolic pressure over diastolic pressure and is measured in millimetres of mercury (mmHg), for example 120/80.Blood pressure varies in healthy people and animals, but its variation is under control by the nervous and endocrine systems. Blood pressure that ispathologicallylow is calledhypotension, and that which is pathologically high ishypertension. Both have many causes and can range from mild to severe.