Manometer
A manometer (muh-nom-i-ter) measures the pressure of gases or liquids using a tube filled with liquid, usually mercury. One end of the tube is closed and contains the gas or liquid to be measured. The other end of the tube is opened.
The manometer in the picture shows:
(A) The open end of the tube. This allows the liquid in the manometer to be influenced by air pressure. (B) The liquid in the tube. Notice the the liquid is higher on the left side than on the right side. (C) The closed end of the tub. In this diagram, this end of the tube is connected to a device submerged in another liquid. By connecting this device to the manometer, the pressure of the liquid in the beaker can be determined (Elfick, 2014). |
When determining the pressure of the gas or liquid being measured, you must determine the change in height (∆h) of the manometer's liquid from one side of the tube to the other. Then, you use a mathematical formula to determine the pressure of the gas or liquid.
A sphygmomanometer (sfig-moh-muh-nom-i-ter), or blood pressure cuff, is used to measure blood pressure. This device uses an inflatable cuff connected to a pump to measure the pressure of the blood pushing against the walls of arteries. The nurse or doctor uses a stethoscope to listen for the pumping of blood through the arteries. The cuff is also connected to a manometer, which uses mercury to define the measurement. By observing the levels of mercury within the manometer, the nurse or doctor can determine a person's blood pressure (Griffith, n.d.).