I have used several different types of water level loggers fo Claudia, I have used several different types of water level loggers for shallow wetland groundwater, pond surface water and to monitor tidal fluctuations. All were pressure transducer type instruments. When I was with the US Geological Survey many years ago, they used instruments that had a float inside a stilling well. That's pretty old technology and I'm not sure if anything like that is currently available on the market. I am slightly familiar with instruments that are mounted on bridges that uses an infra-red signal
to measure the distance down to the water. These are typically used to monitor for flooding conditions at low bridges as a safety precaution. Years ago, small infra-red loggers were used in wells, but I believe the small enclosed space of the well and the high humidity made the readings unreliable. Anyway, all the practical units I am familiar with are pressure transducer types. In my experiance, they fall out in two catagories: 1. sealed and unvented units; such as the Onset water level loggers: http://www.onsetcomp.com/products/data-loggers/u20-001-01 (Solinst is another well know producer of these types) 2. vented cable units with a seperate tranducer at the bottom of the cable and the data logger on top; sucg as the Global water level logger and the Infinities USA loggers: http://www.globalw.com/products/wl16.html http://infinitiesusa.com/Site/Pressure_Water_Level_Data_Loggers.html I have used all three of these instruments and typically price is generally comparable and download time is similar as well. Some manufacturers have field data shuttles for easy download (Infinities uses an old HP calculator), but I'm prettu sure all can be downloaded to a laptop PC. There are distinct advantages between the two types. Type 1. is sealed, so you need an additional logger collecting barometric pressure data outside of the water to correct all your water level/pressure data. These units also have a limited lifespan, since you cannot replace their batteries. I think they can collect data for approx. 4-5 years before the batteries are exhausted. Also, they must be retrieved to download the data. Retrieval and downloading can be pretty simple and take just a few minutes. The advantages of Type 1 is they're very easy to install (put in stilling well or hang from a dock with string) and are inconspicuous (if theft, tampering of vandalism is a potential problem). They are also very rugged. Type 2 loggers have vented data loggers at the top of a cable, therefore the data doesn't need to be corrected with logger barometric data. The batteries in these units can also be replaces. Depending on logging frequency, they'll need to be replaced every 2-5 months. These units can also be downloaded without removing them from the housing, since the data logger is on top an has a screw on top to the USB or serial port for set up and data downloading. The disadvantages of Type 2 is that they are made to length, with a specific cable length connecting the pressure transducer on the bottom to the logger on the top. Also, the logger must be accessible, so they vulnerable to tampering, unless you place them in a locking housing. Also, if the logger is subject to being over topped by water (flooding or storm surge) they can malfunction or be ruined. I'm not sure of the availability in Europe of the specific instruments I've used, but I suspect similar types will be available. Please feel free to email me with any questions. Mike Schening [email protected] >From: Claudia Pogoreutz <[email protected]> >Subject: recommendations water level logger? Dear Listers, I am looking for submersible water level loggers, but the enormous diversity of products on the market has taken me quite aback. I would greatly appreciate any recommendations on this topic. Specifically, I intend to deploy the loggers long-term in shallow lotic environments. Desirable features ideally include long battery life, high logging capacity (memory), fast data download, being able to download the data in the field, and not requiring too much maintenance. (And all of this as inexpensive as possible!) I=92d be happy if anyone can make a recommendation regarding a specific producer, or even model, that has worked well for you! Many thanks in advance. Best fishes, Claudia Pogoreutz, M.Sc. PhD student Senckenberg Research Institute Department of River Ecology and Conservation Clamecystra=DFe 12 63571 Gelnhausen Ph: +49-0170-3602210 Email: [email protected]
