This Rosemount 3108HP2PN1I1 belongs to Emerson 3108 ultrasonic transmitter series specially engineered for open channel flow and liquid level continuous measurement in wastewater, chemical effluent and water treatment industries. Adopting non-contact ultrasonic time-of-flight measuring principle, the unit sends out ultrasonic pulses toward liquid surface and calculates empty distance via echo receiving delay, then converts measured empty distance into real liquid level, further computing instantaneous and totalized open channel flow after relevant flume or weir parameter configuration.

The HP variant features full UPVC sealed construction with integrated built-in external temperature compensation probe to automatically calibrate sound velocity variation caused by ambient temperature shift and eliminate measuring drift error. Equipped with factory pre-installed 2-meter two-core signal cable and 1-inch NPT male thread for overhead suspended mounting, this specific model excludes local site display and provides combined 4–20mA analog plus HART7 digital loop-powered output for direct connection with distributed control system or matching Rosemount 3490 control unit for centralized flow programming and pump interlock control. The suffix I1 stands for full intrinsically safe certification complying with ATEX, IECEx and FM IS standards with Ex ia IIC T6 rating, allowing safe installation inside classified hazardous explosion-prone areas. All internal electronic components are fully factory encapsulated to achieve IP68 ingress protection rating, resisting temporary full submersion and harsh outdoor working conditions with weak acid and alkaline wastewater corrosion. Without movable internal mechanical parts, the transmitter realizes long-term stable operation and greatly reduces routine field maintenance workload after commissioning. Standard measuring effective range covers 0.3 meter up to 3.3 meter with fixed 0.3-meter blind zone, satisfying most conventional Parshall flume and thin-plate weir open channel measurement requirements.

The transmitter internal electronics generate periodic ultrasonic sound pulses which travel downwards through air space to liquid surface; partial sound waves reflect back as echo signal captured by built-in transducer. The circuit module computes flight time between pulse emission and echo reception to figure out empty height from transducer face to liquid surface. After inputting installation base height and open channel geometric parameters including flume type, notch dimension or weir size via HART communicator or matched control unit, the device automatically converts level data into real-time flow rate and accumulates total flow volume continuously. The attached external temperature sensor feeds real ambient temperature data into mainboard to modify sound speed value dynamically and guarantee consistent measuring accuracy across wide temperature fluctuation ranges.

Before field installation, select overhead vacant position above measured open channel avoiding strong water splash, intensive steam accumulation and solid suspended substance disturbance on liquid surface. Fix the unit with matched mounting accessory via 1-inch NPT external thread on installation bracket and keep transducer perpendicular to horizontal liquid plane strictly to prevent echo signal deflection causing measuring failure. Confirm installed vertical distance from transducer bottom to lowest liquid level stays above 0.3-meter blind zone; meanwhile reserve enough safety space to avoid liquid submerging transducer under maximum overflow working condition. Route the pre-attached 2-meter signal cable along fixed wiring channel and keep cable far away from high-power motor or frequency conversion equipment to prevent electromagnetic interference on 4–20mA and HART communication signal. For intrinsically safe installation under explosive hazardous location, strictly follow related IS wiring specification, adopt certified intrinsically safe barrier and limited power supply voltage below rated threshold per I1 certification requirement.

This transmitter applies loop-powered design with DC working voltage ranging from 10.5V to 40V; maximum allowable input voltage is restricted below 30V when deployed in intrinsic safety hazardous area. Connect positive and negative core wires of output cable respectively to DCS system analog input module or Rosemount 3490 control unit loop circuit. The 4–20mA current signal varies linearly corresponding with full measuring span while HART digital signal overlays on analog line to complete remote parameter setup, range modification and real-time fault diagnosis via standard HART field communicator or AMS management software. Control total loop load resistance within 500 ohm maximum to ensure stable signal transmission without distortion.

Complete basic setup by connecting HART hand communicator on signal loop circuit. Enter core configuration items sequentially including empty distance measuring range, installation reference height, corresponding open channel style such as Parshall flume, rectangular weir or V-notch weir and relevant geometric dimension data of selected flow structure. After finishing parameter entry, run single-point calibration at known liquid level position to correct measuring offset error and verify output current matches preset level-flow mapping relation. Adjust measuring update cycle according to field liquid surface fluctuation condition, configurable between 0.5 second and 2 seconds to balance response speed and data stability. Save all confirmed settings into transmitter nonvolatile memory after commission completion.

Carry out regular quarterly site inspection focusing on transducer surface cleanliness, clear accumulated sludge, foam or floating debris blocking ultrasonic emission path to avoid abnormal echo loss and inaccurate measurement. Check cable outer sheath integrity and wiring terminal tightness to rule out short circuit or loose connection issues periodically. Common abnormal condition solutions: if output stays fixed at full-scale value constantly, check actual liquid level falls within blind zone or severe signal echo interference exists; if measured data drifts obviously with ambient temperature change, verify external temperature probe normal connection status; when HART communication fails but 4–20mA output works fine, inspect loop load value and communicator wiring polarity correctness. Do not disassemble sealed transmitter housing arbitrarily to break factory IP68 protection performance, contact official after-sales support for internal component repair once hardware damage is confirmed.

Ambient applicable working temperature spans minus 40 degree Celsius to plus 60 degree Celsius for both running and storage; relative working humidity ranges from 5% to 95% non-condensing atmosphere under atmospheric working pressure with maximum instantaneous withstand pressure at 3 bar. The model owns CE certification plus ATEX, IECEx, FM and CSA intrinsic safety approvals; matched with Rosemount 3490 controller can obtain optional MCERTS environmental measurement certification for official wastewater emission metering compliance on environmental monitoring projects.