A single limb manometer is a type of fluid pressure measuring device that consists of a single vertical column of liquid, usually enclosed in a transparent tube. The column is open at one end to the atmosphere and the other end is connected to the point of measurement. The pressure at a point in a fluid is proportional to the height of the fluid above that point, and in a single limb manometer, the fluid level in the column will rise or fall depending on the pressure at the point of measurement.

Single limb manometers are commonly used in low-pressure measurement applications, such as in HVAC systems and laboratory settings. They are also used to measure small pressure differences, such as in fluid flow experiments and studies. Unlike U-tube manometers, which have two arms and can measure differential pressure, single limb manometers only measure gauge pressure.

Single limb manometers are simple, inexpensive, and easy to use, and are well suited for measuring low-pressure changes in a variety of applications. However, they are limited in their range and accuracy and are not suitable for high-pressure measurements.