The National Ground Water Association’s (NGWA) Research and Education Foundation maintains a collection of historical scientific equipment related to the groundwater industry. In their 2011 Annual Report, NGWA recognized Robinson Noble’s donation of a circa. 1969 Stevens Type F water level recorder to the museum collection. The museum’s collection is hosted online at the Virtual Museum of Ground Water History; the Stevens Type F is located in the “Focus On the Science” wing.
This water level recorder pre-dated the solid-state water level sensors and dataloggers that are widely available today. The unit operated by means of a float and a weight suspended over a pulley via a beaded wire. The beads on the wire meshed with indentations on the pulley such that when water levels changed, the float moved up and down causing the pulley and attached drum to rotate. A pen traced a record of the water level change on chart paper affixed to the drum. The pen moved laterally across the chart paper by means of a clock drive, generating a real-time hydrograph. This model has a wind-up, gear-driven clock drive, but newer models are battery-powered and use quartz clock movements or solid-state circuitry.