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An open (differential) mercury pressure gauge. A mercury pressure gauge is a type of manometer using mercury as the working fluid. The most basic form of this instrument is a U-shaped glass tube filled with mercury. More complex versions deal with very high pressure or have better means of filling with mercury.
Typically it is filled with mercury. If used incorrectly, this mercury can escape and contaminate the vacuum system attached to the gauge. McLeod manometer symbol according to ISO 3753-1977 (E) McLeod gauges operate by taking in a sample volume of gas from a vacuum chamber, then compressing it by tilting and infilling with mercury.
A sphygmomanometer (/ ˌ s f ɪ ɡ m oʊ m ə ˈ n ɒ m ɪ t ə r / SFIG-moh-mə-NO-mi-tər), also known as a blood pressure monitor, or blood pressure gauge, is a device used to measure blood pressure, composed of an inflatable cuff to collapse and then release the artery under the cuff in a controlled manner, [1] and a mercury or aneroid manometer to measure the pressure.
Pressure range, sensitivity, dynamic response and cost all vary by several orders of magnitude from one instrument design to the next. The oldest type is the liquid column (a vertical tube filled with mercury) manometer invented by Evangelista Torricelli in 1643. The U-Tube was invented by Christiaan Huygens in 1661.
Mercury manometers were the first accurate pressure gauges. They are less used today due to mercury's toxicity, the mercury column's sensitivity to temperature and local gravity, and the greater convenience of other instrumentation. They displayed the pressure difference between two fluids as a vertical difference between the mercury levels in ...
The use of mercury manometers is often required in clinical trials and for the clinical measurement of hypertension in high-risk patients, such as pregnant women. A cuff of the appropriate size [12] is fitted snugly, then inflated manually by repeatedly squeezing a rubber bulb until the artery is completely occluded.
Hence, cuff pressure is lowered and the overall blood volume remains constant. As blood volume and thus PG is held constant over time, the pressure difference between cuff pressure and intra-arterial pressure is zero. Intra-arterial pressure is equal to cuff pressure, which can easily be measured by means of the manometer M. [citation needed]
He was interested in the flow of human blood in narrow tubes, and invented the U-tube mercury manometer (or hemodynamometer) to measure arterial blood pressures in horses and dogs. [ 5 ]