The instrument shall give measurements at an accuracy of ± 0.5% of the measured value. All flow meters shall be calibrated and calibration certificates submit for each flow meter. 4.4.2 Ultrasonic Doppler Flow Meter Ultrasonic Doppler flow meters shall be used for situations where a continuous volumetric flow measurement of a liquid containing solids in a closed pipe is required for monitoring purposes. The ultrasonic Doppler flow meter shall consist of a transducer and transmitter. The transducer and transmitter will be separate units with an interconnecting cable. The transducer shall be an inline unit, supplied with a wetted sensor installed in a flanged section of pipe. The transducer shall emit ultrasonic signals into the pipe which will strike solids carried by the liquid flow, deflecting the ultrasonic signals back to the transducer. The deflection will cause the received signals to be frequency shifted, the frequency shift being proportional to the flow rate. The transmitter shall be a microprocessor based unit with an integral operator interface housed within a corrosion resistant enclosure. The operator interface shall have a numeric display, bar graph display and a simple push button interface. All error codes, process variables, configuration data or other internal values shall be accessible and capable of being displayed on the integral operator interface. It shall be possible to limit access to configuration data parameters by means of a configuration password. The transmitter will be powered from a 110 V AC or 18 V to 30 V DC supply. Output shall be by 4 mA to 20 mA current loop which shall be proportional to the measured value. A digital output shall also be provided, configured to generate an alarm in the event of a system failure, and a total flow pulse output. The measurement system shall give a measurement accurate to ± 1% of the measured value. 4.4.3 Ultrasonic Transit Time Flow Meter Ultrasonic transit time flow meters shall be used for situations where a continuous volumetric flow measurement of a liquid containing no solids is required for monitoring purposes. The ultrasonic transit time flow meter shall consist of a transducer and a transmitter unit with interconnecting cabling. The transducer shall be an inline unit, supplied with a pair of wetted sensors installed in a flanged section of pipe. The sensors shall be located such that the signal path is diagonal across the pipe, passing through the central axis of the pipe. Each sensor shall emit ultrasonic signals across the pipe which will be received by the opposing sensor. Due to the sensor location, the two signal paths shall differ. In one direction, the ultrasonic signals shall be travelling in the direction of liquid flow, whilst in the other direction, the ultrasonic signals will be travelling against the direction of liquid flow. The flow rate shall be calculated from the difference in transit time between the two signal paths. The transmitter shall be a microprocessor based unit with an integral operator interface housed within a corrosion resistant enclosure. The operator interface shall have a numeric display, bar graph display and a simple push button interface. All error codes, process variables, configuration data or other internal values shall be accessible and capable of being displayed on the integral operator interface. It shall be possible to limit access to configuration data parameters by means of a configuration password. The transmitter will be powered from a 110 V AC or 18 V to 30 V DC supply. Output shall be by 4 mA to 20 mA current loop which shall be proportional to the measured value. A digital output shall also be provided, configured to generate an alarm in the event of a system failure, and a total flow pulse output. Page 118