Abstract: Fluid flowing in an open channel or aqueduct having a notched dam or weir produces a hydraulic head at the weir which is proportional to the rate of flow of the fluid in the aqueduct. A sampling device is provided in association with the aqueduct just upstream from the weir which is adapted to scoop up a sample of the flowing fluid in a quantity which is proportional to the hydraulic head. That quantity of fluid may then be measured as a function of the flow rate.

Abstract: A signal correlator for correlating pulse pairs received over a data transmission line as alternating positive and negative pulses representing data "1's" and "O's." The reception of a logic "1" is affirmed by testing for a negative polarity pule pulse an initial positive polarity pulse received over the transmission line. Conversely, the reception of a logic "O" is affirmed by testing for a positive pulse following an initial negative pulse received over the transmission line. The first pulse of a pulse pair received over the transmission line is temporarily stored in a flip-flop and the stored pulse value is compared by a comparator with the second pulse when it arrives. An error signal is developed by the comparator in the event that an error is detected between the stored pulse value and the second pulse with which it is compared in either pulse pair combination.

Abstract: A thermal recorder having an analog recording stylus and a digital recording head uses a stepping drive means for intermittently driving a thermally responsive recording medium past the analog recording stylus and digital recording head. The analog recording stylus is maintained in contact with the intermittently driven recording medium which the digital recording head is mounted on one end of a pivoted support arm. A solenoid is connected to the other end of the support arm and is selectively energized to bring the digital recording head into contact with the recording medium during the interval between the stepped movements of the recording medium when the recording medium is at rest.

Abstract: A closed system couples the inlet and outlet pressures generated by a centrifugal pump to a pair of flexible diaphragms which seal the flow tube in a pressure rebalance system for measuring fluid flow. The system is filled with a conducting fluid which forms certain resistance paths whose resistance varies with diaphragm position. This resistance change is used to generate signals which control the pump motor to the end that the diaphragms maintain a predetermined position and the pump head is equal to the differential pressure.