| 摘要 |
This is a specialized hand-held and battery-powered unit for field testing of backflow valves. It displays and prints a permanent record of simultaneous source- and discharge-port pressure values and their difference. To reduce operator distraction and confusion during backflow tests the source and discharge values are automatically equalized, bringing the difference to zero, whenever the actually sensed pressures are within a threshold differential such as 0.2 pounds per square inch. Preferably two pressure sensors are provided for connection to source and discharge ports respectively, yielding independent analog electrical signals representing the pressures; and two independent analog-to-digital converters respond to the two sensor signals respectively. Digital input signals from the converters pass to a microprocessor-which controls a digital display to show the three values continuously. The processor also controls an onboard printer to record the same values, together with elapsed time, at regular intervals such as two seconds. In the record are automatically recorded test parameters, which for integrity of the record include some data settable only at the factory: testing-device serial number, operator name and regulatory-agency license number, and serial number and date of the test itself.
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