Clark Sonic Series CSLFB Brass Ultrasonic Liquid Flow Transmitter Manual0 pages

Rev112011 USER MANUAL CLARK SONIC® MODEL CSLFB The Model CSLFB is an ultrasonic transit time flow meter designed to accurately and reliably report the flow of non-compressible fluids in pipe diameters ranging from % inch to 2 inches. It is a 2- wire device reporting flow in the industry standard 4-20 mA protoͭcol. The meter introduces no pressure drop other than the pipe section which provides the means to position the ultrasonic transducers and to connect to the user's piping system. The small electronic board which implements all the func-tions to measure and report the flow is housed in the integral brass meter body and is sealed so as to protect the electronics from the environment. THEORY OF OPERATION Two ultrasonic transducers are positioned and angled so as to transmit and receive sound pulses that are launched at a flat reflec-tion point located on the opposing side of the pipe. The flight time of the sound pulse from the transmitting transducer to the receiving transducer will be shortened if the pulse is launched in the direction of flow and increased if launched opposite to the direction of flow. By alternating the transmitting and receiving transducers, the differͭence in these transit times can be used to calculate the velocity of the flow, which when multiplied by the area of the pipe, results in a measure of volumetric flow rate which is then used to set the current in the 4-20 ma loop proportional to the full scale value of the meter. The path of this sonic pulse traverses the pipe diameter twice and because of the generous spacing between transducers, the volume of fluid which influences the time of flight of this pulse is commensurate with the scale of the turbulence features in the flow. Turbulence by its nature has chaotic velocity components and by directing the sonic pulse through a volume comparable to the scale of this chaos, the effect on the flight time on any single measure-ment are much reduced, resulting in measurements that show less variation from the average. Stating it another way, a measure of the Standard Deviation of a number of measurements will be reduced, resulting in less uncertainty in the currently reported flow rate. clark USER MANUAL MODEL CSLFB ULTRASONIC FLOW TRANSMUTER Clark Solutions 10 Brent Drive, Hudson, MA 01749 Tel. 978 / 568 3400 Fax 978 / 568 0060 www.clarksol.com IMPLEMENTATION The accuracy and precision of the determined flow rate is ultimately determined by the accuracy and precision with which one can measure the transit times.