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ECH2O Probe User's Manual <br />4. Collecting Data <br />0 <br />1 4. Collecting Data <br />NOTE: ECH20 probes are intended only for use with <br />dataloggers and readout devices which can provide short <br />excitation pulses, leaving the probes turned off most of <br />the time. Continuous excitation not only wastes battery <br />power, but may, under certain circumstances, cause the <br />probe to exceed government specified limits on electro- <br />magnetic emissions. <br />11 <br />�7 <br />Datalogger Requirements <br />The ECH2O sensors are designed to work most efficiently <br />with Decagon's 5 -channel Em5, Em50 or our ECH20 <br />Check handheld readout. They can, however, be adapted <br />for use with other dataloggers, such as those from Camp- <br />bell Scientific, Inc., for example. The ECH2O requires an <br />excitation voltage in the range of 2 to 5 volts. It produces <br />an output voltage that depends on the dielectric constant <br />of the medium surrounding the probe, and ranges <br />between 10 and 50% of the excitation voltage. Any data - <br />logger which can produce a 2.5 to 5V excitation with <br />approximately 10 millisecond duration and read a volt - <br />level signal with 12 -bit or better resolution should be com- <br />ompatible <br />patiblewith the ECH2O probes. For the EG 10 and EG <br />20 probes, the current requirement at 2.5V is around <br />2mA, and at 5V it is 7-8n A. For the EC -5, it is 10mA at <br />2.5V. <br />NOTE: ECH20 probes are intended only for use with <br />dataloggers and readout devices which can provide short <br />excitation pulses, leaving the probes turned off most of <br />the time. Continuous excitation not only wastes battery <br />power, but may, under certain circumstances, cause the <br />probe to exceed government specified limits on electro- <br />magnetic emissions. <br />11 <br />�7 <br />