YSI Pro20+ Dissolved Oxygen Meter with Integrated Stirring BOD Probe

Overview

The YSI Pro20+ Dissolved Oxygen Meter with Integrated Stirring BOD Probe is a field-deployable, multi-parameter water quality analyzer engineered for high-reproducibility dissolved oxygen (DO) measurements in biochemical oxygen demand (BOD) testing, wastewater monitoring, environmental surveys, and laboratory process validation. Unlike conventional galvanic or polarographic DO probes requiring external stirring or manual agitation, this system incorporates a motor-driven integrated stirrer within the probe assembly—ensuring consistent hydrodynamic conditions across samples and eliminating operator-induced variability during BOD incubation. The instrument operates on Clark-type electrochemical principles: for polarographic mode, it applies a polarizing voltage to reduce oxygen at the cathode; for galvanic mode, it leverages spontaneous redox potential between dissimilar metals. Both sensor types are interchangeable via the modular 60520-series temperature-compensated cable interface, enabling rapid configuration for field or lab use. The built-in barometer provides real-time atmospheric pressure compensation—critical for accurate DO reporting per ASTM D888 and ISO 5814—while the dual backlight LCD and tactile keypad support operation under low-light conditions common in wastewater treatment plants or nocturnal ecological sampling.

Key Features

• Integrated mechanical stirrer housed directly within the BOD probe (model 605780), delivering uniform flow velocity across the sensing membrane—essential for compliance with EPA Method 410.4 and Standard Methods 4500-O G
• Sub-10-second 95% response time using standard Clark-type membranes—among the fastest documented for handheld DO instruments in routine BOD applications
• One-button auto-calibration sequence: initiates zero-point and saturation calibration simultaneously, applies barometric correction, and stores calibration coefficients—all within 3 seconds
• Modular three-component architecture: host meter, detachable cable (1/4/10/20/30 m options), and swappable probe—each independently replaceable without tools or service downtime
• MIL-spec waterproof connector rated for >300,000 mating cycles and IP67 ingress protection—validated for submersion up to 1 m for 30 minutes and survivability after 1-meter free-fall impact
• Dual-mode DO sensing: user-selectable galvanic (605202) or polarographic (605203) electrodes, both thermally compensated via co-located NTC thermistor in the 60520-series cable
• Onboard data logging for 50 discrete measurement records—including timestamp, DO, temperature, conductivity, salinity, TDS, and barometric pressure

Sample Compatibility & Compliance

The Pro20+ with stirring BOD probe is validated for aqueous matrices including raw and treated wastewater, surface water, groundwater, effluent streams, and laboratory BOD dilution water. Its robust stainless-steel probe guard and chemical-resistant silicone membrane ensure stability in abrasive or particulate-laden samples. The system meets regulatory requirements for environmental monitoring under US EPA, ISO, and ASTM frameworks: DO accuracy aligns with ASTM D888 Class II specifications; barometric compensation satisfies ISO 5814:2012 Annex A; and the integrated stirrer design conforms to the hydrodynamic criteria outlined in APHA Standard Methods 4500-O G for BOD5 assays. While not intrinsically rated for hazardous locations, its IP67 enclosure and sealed battery compartment permit safe deployment in humid, outdoor, or splash-prone environments typical of municipal infrastructure and field ecology studies.

Software & Data Management

The Pro20+ operates as a standalone instrument with no mandatory PC dependency. All calibration parameters, date/time settings, and unit preferences are retained in non-volatile memory—even after battery replacement. Data export is performed manually via visual readout or recorded externally using standardized field notebooks. Although the device lacks Bluetooth or USB connectivity, its firmware supports field-upgradable calibration algorithms through YSI’s authorized service centers—ensuring long-term traceability and alignment with evolving metrological standards such as ISO/IEC 17025. Audit trails are maintained via physical logbooks compliant with GLP documentation practices; electronic data integrity is preserved by minimizing digital dependencies that could introduce uncontrolled variables in regulated BOD workflows.

Applications

• Routine 5-day BOD testing in wastewater treatment facilities, per EPA Method 405.1 and ISO 5815-1
• Field verification of DO saturation levels upstream/downstream of aeration basins or spill events
• Ecological monitoring of hypolimnetic oxygen depletion in stratified lakes and reservoirs
• Validation of membrane integrity and electrolyte stability in polarographic/galvanic sensors
• Educational laboratory instruction on respiration kinetics, microbial activity, and oxygen mass transfer
• QA/QC checks for DO sensor drift during extended deployments in remote monitoring stations

FAQ

Does the integrated stirrer require separate power or control wiring?
No—the stirrer motor is powered directly through the same cable that supplies the DO sensor and temperature circuitry. No additional connectors or external drivers are needed.
Can the stirring BOD probe (605780) be used with older Pro20 or Pro10 series hosts?
No—it is electrically and mechanically compatible only with the Pro20+ host (firmware v2.1 or later) due to revised power delivery protocols and motor driver integration.
Is barometric compensation mandatory for accurate DO readings?
Yes—partial pressure of oxygen varies with local atmospheric pressure; omission introduces systematic bias exceeding ±0.5 mg/L at elevations >500 m above sea level. The built-in barometer ensures compliance with ISO 5814 and ASTM D888 reporting requirements.
What maintenance is required for the stirring mechanism?
The brushless DC motor is sealed and lubricated for life. Routine cleaning of the stirrer vanes with deionized water and soft brush is recommended after exposure to viscous or biofouling samples.
How does the Pro20+ handle salinity compensation during DO measurement?
It applies temperature- and salinity-corrected solubility coefficients per Weiss (1970) equations, using either user-entered ppt values or real-time conductivity-derived salinity—enabling accurate DO reporting in estuarine or brackish water applications.