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U.S. Geological Survey Open-File Report 2009-1101

## **The Partition Intervalometer: A Programmable  Underwater Timer for Marking Accumulated Sediment Profiles Collected in Anderson Sediment Traps: Development,  Operation, Testing Procedures, and Field Results**

| Title PageIntroductionDevelopmentFunction and OperationTesting Procedures and ResultsResults of Field TestsSummaryAcknowledgmentsReferencesList of FiguresAppendix 1:       Programming the Intervalometer Appendix 2:       Synopsis of Field Notes 
  | **By Richard R. Rendigs, Roger Y. Anderson, Jingping  Xu, Raymond E. Davis, and Emile Bergeron**

**Published 2009**
Abstract
This manual illustrates the development of a programmable  instrument designed to deploy a series of wafer-shaped discs (partitions) into the  collection tube of a sediment trap in various aquatic environments. These hydrodynamically  shaped discs are deployed at discrete time intervals from the Intervalometer and  provide markers that delineate time intervals within the sediments that  accumulate in the collection tube.

The timer and  mechanical system are lodged in an air-filled, water-tight pressure housing that  is vertically hung within the confines of a cone-shaped sediment trap. The  instrumentation has been operationally pressure tested to an equivalent water  depth of approximately 1 km.

Flaws discovered  during extensive laboratory and pressure testing resulted in the implementation  of several mechanical modifications (such as a redesign of the rotor and the  discs) that improved the operation of the rotor assembly as well as the release  of discs through the end cap. These results also identified a preferred azimuth  placement of the rotor disc relative to the drop hole of the end cap. 

In the  initial field trial, five sediment traps and coupled Intervalometers were attached  to moored arrays and deployed at two sites off the coast of Southern California for approximately 8  months. Each of the instruments released 18 discs at the programmed 10 day  intervals, except one unit, which experienced a malfunction after approximately  4 months. Most of the discs oriented in a near-horizontal position upon the  surface of the sediment in the collection tubes. Sampling of the sediments for  geochemical analyses was improved by these clearly defined markers, which indicated  the changes in the flux and nature of sediments accumulated during the  deployment period of each sediment trap.
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U.S. Department of the Interior |		U.S. Geological Survey		                                    URL: https://pubsdata.usgs.gov/pubs/of/2009/1101/		Page Contact Information: Contact USGS		Page Last Modified: Wednesday, 07-Dec-2016 21:54:48 EST