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Procedure for Testing Liquid -Float Switch Sensors <br /> Application <br /> This procedure applies to liquid -float switches that are used for underground <br /> storage tank applications . It does not apply to external groundwater monitoring <br /> detectors . Each sensor should be tested in the products for which they are to be used . <br /> For a typical gasoline station this would include gasoline , diesel fuel , and water . <br /> Procedure <br /> 1 . Mount the sensor in a vertical cylinder with a known , uniform diameter from top to <br /> bottom . The sensor should be securely fastened so that it is in contact with the <br /> cylinder bottom in its normal orientation . <br /> 2 . Add liquid ( product or water) to the cylinder from a buret capable of reading <br /> volume to the nearest 0 . 2 ml . Liquid should be added in increments until the <br /> sensor responds to the liquid . Adequate time should be allowed between <br /> increments for all the sensors to respond if the response time is not <br /> instantaneous . <br /> 3 . When the approximate threshold has been determined , the sensor should be <br /> removed and the cylinder dried out for a repeat measurement . <br /> 4 . For subsequent measurements , liquid may be added quickly to just below the <br /> threshold level . <br /> 5 . Liquid should then be added very slowly until the sensor responds . <br /> 6 . Steps 3 through 5 should be repeated a minimum of 6 times for each liquid . <br /> 7 . Record all information in an appropriate manner . <br /> Calculations <br /> The cross sectional area of the test cylinder and the sensor must both be <br /> determined . The difference in cross section is used in the calculations . <br /> The test cylinder cross section is determined from the equation : <br /> Ac = 1Lr2 <br /> where Ac is the cross section of the cylinder and r is the radius of the cylinder . <br /> If the geometry of the sensor is uniform , it may be possible to calculate the cross <br /> sectional area using the appropriate equations . If the geometry is irregular, the <br /> displacement of the sensor must be empirically determined before the calculations can <br /> be completed . It is usually preferable to calculate the cross section when possible . <br /> Liquid-Float Switch Sensors Page 1 of 2 <br />