Hengao HAD-S118G Portable Fluorescence-Based Dissolved Oxygen Meter
| Brand | Hengao |
|---|---|
| Origin | Beijing, China |
| Manufacturer Type | Authorized Distributor |
| Origin Category | Domestic |
| Model | HAD-S118G |
| Pricing | Available Upon Request |
Overview
The Hengao HAD-S118G Portable Fluorescence-Based Dissolved Oxygen Meter is an optical sensor system engineered for high-accuracy, maintenance-free measurement of dissolved oxygen (DO) in aqueous environments. Unlike electrochemical Clark-type sensors—whose performance degrades due to membrane fouling, electrolyte depletion, and oxygen consumption during measurement—the HAD-S118G employs solid-state fluorescence quenching technology grounded in the Stern–Volmer principle. A blue LED excites a proprietary oxygen-sensitive fluorophore immobilized on the sensor surface; molecular oxygen (O₂) dynamically quenches the resulting red fluorescence, shortening its lifetime in direct proportion to DO concentration. This lifetime-based detection eliminates drift from photobleaching or intensity fluctuations, delivering stable, absolute measurements independent of sensor orientation, flow rate, or sample turbidity. The instrument is calibrated traceably to NIST-traceable standards and conforms to ISO 5814:2012 (Water quality — Determination of dissolved oxygen — Electrochemical probe method) and ASTM D888-22 (Standard Test Methods for Dissolved Oxygen in Water), with optical methodology validated for compliance in GLP and environmental monitoring workflows.
Key Features
- Fluorescence lifetime detection: Measures phase shift or decay time of red emission (620–680 nm), not intensity—ensuring immunity to light scattering, biofouling, and ambient light interference
- No oxygen consumption: Non-invasive optical sensing preserves sample integrity and enables continuous monitoring without perturbing the aquatic system
- Zero-maintenance operation: No electrolyte refills, no membrane replacements, no polarization time required—ready for use immediately after power-on
- Integrated compensation: Automatic full-range temperature compensation (−5 to 50 °C), barometric pressure correction (51–112 kPa), and user-selectable salinity compensation (0–55 ppt)
- Rugged field design: IP67-rated ABS housing, PET replaceable sensor cap, and corrosion-resistant optical window suitable for freshwater, seawater, wastewater, and industrial process streams
- Intuitive interface: Backlit 6.6 cm × 3.6 cm monochrome LCD with real-time display of DO (mg/L), saturation (%), temperature (°C), pressure (kPa), and salinity (ppt)
Sample Compatibility & Compliance
The HAD-S118G is validated for use across diverse aqueous matrices including potable water, surface water, groundwater, estuarine and marine systems, activated sludge, bioreactors, aquaculture tanks, and cooling tower fluids. Its optical architecture eliminates interference from hydrogen sulfide, chlorine, heavy metals, or suspended solids that commonly affect amperometric sensors. The device meets regulatory requirements for field-deployable DO measurement under EPA Method 360.1 (Dissolved Oxygen—Electrochemical Probe Method) and supports data integrity in ISO/IEC 17025-accredited laboratories. While not FDA 21 CFR Part 11–compliant out-of-the-box (no electronic signature or audit trail), raw measurement logs exported via USB are compatible with LIMS integration for controlled documentation.
Software & Data Management
The meter stores up to 500 timestamped readings internally (date, time, DO, temp, pressure, salinity). Data export is supported via micro-USB to CSV format for post-processing in Excel, MATLAB, or environmental reporting platforms (e.g., EQuIS, ArcGIS). No proprietary software is required—standard USB mass storage mode enables drag-and-drop file retrieval. Calibration history (zero and span points, date/time stamps) is retained in non-volatile memory. Firmware updates are delivered as signed binary files via Hengao’s technical support portal, ensuring version control and traceability.
Applications
- Environmental monitoring: Field validation of DO profiles in rivers, lakes, and coastal zones per USGS NWIS protocols
- Wastewater treatment: Real-time aeration basin optimization and effluent compliance verification against NPDES permit limits
- Aquaculture management: Hypoxia risk assessment in shrimp ponds and salmon raceways using saturation % thresholds
- Research & education: Undergraduate limnology labs, graduate biogeochemistry studies, and sensor validation experiments
- Industrial process control: Monitoring DO in pharmaceutical bioreactors, beverage fermentation tanks, and boiler feedwater systems
FAQ
Does the HAD-S118G require calibration before each use?
No. Factory calibration is stable for ≥6 months under normal field conditions. A single-point air-saturation check (100% DO at local temperature/pressure) is recommended before critical measurements.
Can it measure in highly turbid or colored water?
Yes. Fluorescence lifetime detection is unaffected by optical attenuation—unlike absorbance-based methods—making it suitable for algal blooms, peat-stained waters, and digester supernatants.
Is the sensor cap replaceable in the field?
Yes. The PET-based optical cap is user-replaceable with standard tools; replacement kits include calibration certificate and torque specification.
What battery life can be expected during continuous logging?
With alkaline AA cells, ≥30 hours of active measurement time is achievable; auto-power-off after 10 minutes of inactivity extends field deployment.
How is pressure compensation implemented?
An onboard piezoresistive barometer continuously measures ambient atmospheric pressure; the firmware applies the ideal gas law correction to convert partial pressure to concentration (mg/L) per ISO 5814 Annex B.
