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I] <br />u <br />P <br />11 <br />I <br />7 <br />per-. <br />lJ' <br />11 <br />it <br />n <br />r <br />Drain Gauge User's Manual <br />4. Collecting Data <br />from the Em50, so the drainage reported is the cumulative <br />amount since the Em50 memory was last erased. The <br />Em50 will also output the water depth sensor mV reading <br />at each wake interval. <br />Other Data LoggingSvsTms <br />The Drain Gauge can also be adapted for use with other <br />data loggers, such as those from Campbell Scientific, Inc. <br />The Drain Gauge sensor requires an excitation in the <br />range of 2-5 volts. Any data logger which can produce a 2- <br />5 V excitation with approximately 10 millisecond duration <br />and read a volt -level signal with 12 bit or better resolution <br />should be compatible with the Drain Gauge. The current <br />requirement at 2.5 V is around 2 mA, and at 5V it is 7- <br />8mA. The calibration equations presented in this manual <br />are only valid for a 2.5 V excitation. If another excitation is <br />chosen, 'then the user will need to calibrate the water <br />depth sensor by injecting water into the clear calibration <br />tube and recording the mV output of the sensor after each <br />incremental injection. <br />Important Considerations <br />1. The Drain Gauge sensor is intended only for use with <br />data loggers and readout devices which can provide <br />short excitation pulses. Continuous excitation not only <br />wastes battery power, but may, under certain circum- <br />stances, cause the sensor to exceed government speci- <br />fied limits on electromagnetic emissions. <br />2. All Decagon readout devices use 2.5V excitation, so <br />the remainder of the discussion assumes this as the <br />excitation. If other voltages are used, adjustments to <br />the calibration equations provided will be needed. <br />23 <br />