May 16, 2002 -- Sewage system overflows are a pressing problem. It's vitally important to know how often they occur and how much water is concerned each time. Suitable measures can be taken on the basis of this information.
The Sewer Datalogger from Van Essen Instruments can provide accurate measurements and an overflow report.
The datalogger is a self-recording instrument specially developed for the automatic recording of sewage system overflows. The instrument measures the water level in the sewage system with its built-in pressure gauge and stores the data in its internal memory. The memory can be accessed using a readout unit attached to a (portable) PC.
The datalogger consists of two connected parts, the measuring unit and the communications unit. Placing the readout unit on the communications unit establishes a link between the computer and the datalogger. Using the EnviroMon software, the instrument can be programmed to increase the frequency of measurements while an overflow is actually taking place.
The datalogger's measuring unit is hung in the sewer drain, below the top of the overflow wall. The in-built pressure gauge enables the it to measure the water level extremely accurately. The data obtained, the sewer water levels and the times at which they were measured, are stored in its internal memory up to a maximum of 16,000 measurements. This is more than sufficient to monitor the overflow location accurately for a lengthy period. Once installed, the communications unit is located just under the manhole cover.
The connection between measuring unit and the communications unit consists of a tough optic-fibre cable. The communications unit contains an ingenious system for barometric compensation. In order to ensure its long-term stability and high level of accuracy, the datalogger carries out an automatic calibration every day. This involves checking the zero point during a dry period. The whole system is powered by an internal battery with an 8-10 year lifespan.
The datalogger is constructed entirely of stainless steel and is impervious to corrosive chemicals in the sewer. Interference from moisture is eliminated by its completely sealed design. The datalogger's compact dimensions and handy suspension mechanism make it easy to install without having to enter the sewer itself. Nothing can be seen on the outside of the sewer system, which helps prevent vandalism.
The information stored in the datalogger's internal memory can easily be accessed using the readout unit and a (portable) computer. The data is transferred directly into the computer and can be presented in the form of a chart or graph, using EnviroMon.
The report menu offers the option of automatically generating an overflow report for standard situations. Facilities for exporting the data to spreadsheet programs are also included. The datalogger's memory can be read out at any chosen time, again without having to enter the sewer itself.
