A manometer is a type of pressure gauge. Specifically, it is a type of gauge that uses a column of liquid to indicate and measure the pressure, in terms of force applied.
At its most basic, a manometer is a tube with a “U” shape that is filled with liquid. At normal household pressure the two columns of liquid, one on each side of the “U,” will be at the same hight. Pressure is then applied to one end of the tube. The liquid in one side of the “U” is pushed down and the other column goes up. This increase in height represents the force applied.
How are manometers used with Highland bagpipes?
The common type of manometer used with bagpipes is the U-tube manometer. This is usually a long, clear, silicone tube that is filled with water or some other stable liquid. One end of the tube will be open to the air and the other will be inserted into one of the drone tops.
When air is blown into the bagpipe it causes the column of liquid to move giving a representational value of pressure. Highland bagpipers can use this column of liquid to diagnose the quality of their overall blowing steadiness while playing the instrument. Unsteady blowing that fluctuates wildly will cause the column to "bounce" up and down. Steady blowing, where fluctuations are minimal, will cause the column of liquid to remain stable and in place based on the piper's playing pressure. This visual feedback can be useful for making improvements to one's sound production on the bagpipe.
Another popular type of bagpipe manometer is the dial gauge. This is actually called a Bourdon Gauge. The principle is the same, pressure force is being measured. In the Bourdon gauge a curved, flattened closed-end tube is connected at the open end to pipe. This pipe is then connected to the pressure force to be measured. As the force is applied it causes the tube to open causing the dial to move.