depthrod

A depthrod is a measuring instrument used to determine the depth of a liquid or the distance to a submerged surface. It consists of a rigid or telescoping rod marked with depth units, such as centimeters or inches, and is designed to be lowered vertically into the fluid. When the end of the rod contacts the bottom or another reference surface, the reading on the scale indicates the depth from the liquid surface to that point. Depth rods are used in laboratories, aquaculture, hydrological studies, and field work where quick, low-tech depth measurements are needed.

Construction and operation vary by model. Simple depth rods are straight, rigid sticks with etched or printed scales. More advanced versions may be retractable or telescoping, sometimes mounted on a reel or handle to control deployment. Some rods include a weighted tip to help maintain vertical alignment, while others are designed for use with a separate measuring line. Digital or electronic variants may incorporate a sensor or depth counter, but the core principle remains a vertical measurement of depth.

Variants and related devices include folding or telescoping depth rods, freshwater or marine versions tailored to specific water conditions, and rods paired with containers, tanks, or wells for controlled measurements. While acoustic sounding and sonar provide depth information without direct contact, depth rods offer a simple, immediate, and robust method for obtaining depth readings in situations where contact measurement is practical and straightforward.

Applications span hydrology, limnology, aquaculture, construction, and routine tank or well inspections. Limitations include sensitivity to tilting, currents, or turbidity, which can affect accuracy, and a need for stable vertical positioning and proper calibration.