YSI Pro20i Portable Dissolved Oxygen and Temperature Meter

Overview

The YSI Pro20i Portable Dissolved Oxygen and Temperature Meter is a field-deployable, ruggedized electrochemical analyzer engineered for high-reliability measurement of dissolved oxygen (DO) and temperature in diverse aquatic environments. It employs a polarographic Clark-type sensor principle—where molecular oxygen diffuses through a gas-permeable membrane and undergoes reduction at a cathode under a fixed polarization voltage—enabling stable, low-drift measurements with minimal maintenance. Designed specifically for environmental monitoring workflows requiring regulatory-grade data integrity, the Pro20i delivers traceable, reproducible results across freshwater, marine, wastewater, and process water applications. Its dual-channel architecture simultaneously acquires DO (mg/L and % air saturation), temperature (°C), and barometric pressure (kPa), with automatic pressure compensation applied in real time during calibration and measurement—critical for compliance with ASTM D888, ISO 5814, and EPA Method 360.5 protocols.

Key Features

• User-replaceable polarographic DO probe with factory-calibrated membrane and electrolyte kit—no tool required for field electrode servicing.
• Fast response kinetics: reaches 95% of final reading within 8 seconds using standard membrane configuration—among the shortest stabilization times documented for portable polarographic systems.
• One-button calibration sequence completes full DO zero and span calibration—including automatic barometric pressure readout and compensation—in under 3 seconds.
• IP67-rated enclosure with physically isolated battery and electronics compartments: submersion up to 1 m for 30 minutes poses no risk to circuit integrity, even if battery compartment floods.
• High-cycle durability: cable strain relief rated for ≥300,000 flex cycles; stainless-steel probe guard provides mechanical protection during deployment in rocky or debris-laden waters.
• Backlit LCD display with luminous keypad enables operation under low-light conditions—including nocturnal sampling or turbid underwater profiling.
• Internal memory stores 50 complete measurement records (DO, temp, pressure, timestamp, user ID), eliminating manual transcription errors and supporting basic GLP-compliant data traceability.
• Extended battery life: 400 hours of continuous operation on two C-cell alkaline batteries, with low-power indicator and auto-sleep mode to conserve energy between readings.

Sample Compatibility & Compliance

The Pro20i is validated for use in natural surface waters (rivers, lakes, estuaries), seawater (up to 70 ppt salinity), aquaculture systems, wastewater treatment influent/effluent streams, fermentation bioreactors, and industrial cooling towers. Its polarographic sensor exhibits minimal interference from common ions (Cl⁻, NO₃⁻, SO₄²⁻), hydrogen sulfide (<50 µg/L), and moderate turbidity. The instrument conforms to RoHS, CE, and WEEE directives. Its IP67 rating meets IEC 60529 requirements for dust-tight and temporary immersion resistance. Drop-test certification per MIL-STD-810G (1 m concrete impact) ensures survivability in rugged field deployments. While not FDA 21 CFR Part 11–certified out-of-box, its immutable timestamped data logs support audit-ready documentation when integrated into validated laboratory information management systems (LIMS).

Software & Data Management

Data retrieval is performed via direct USB connection to Windows-based PCs using YSI’s free ProSolo software (v3.2+). The software enables batch export to CSV or Excel-compatible formats, graphical trend visualization, calibration history review, and metadata annotation (site ID, operator, depth, notes). All stored records include embedded UTC timestamps, pressure-corrected DO values, and raw sensor voltages—facilitating retrospective uncertainty analysis. No proprietary cloud platform is required; local storage preserves data sovereignty and aligns with institutional IT security policies. Audit trails are maintained through software-generated log files tracking calibration events, firmware updates, and memory writes—supporting GLP and ISO/IEC 17025 documentation requirements.

Applications

• Regulatory ambient water quality monitoring per EPA Region-specific TMDL programs and EU Water Framework Directive (WFD) reporting.
• Rapid-response emergency assessment following chemical spills, algal blooms, or hypoxic event detection.
• Academic and research fieldwork in limnology, marine biology, and environmental engineering curricula.
• Real-time DO control in recirculating aquaculture systems (RAS) and aquarium life-support infrastructure.
• Process validation and routine QC in municipal wastewater treatment plants—particularly in aeration basin optimization and nitrification monitoring.
• Bioprocess development labs measuring oxygen uptake rate (OUR) in aerobic fermenters and bioreactors.

FAQ

What calibration standards are required for the Pro20i?
A zero-oxygen solution (e.g., sodium sulfite) and a saturated air standard (at known atmospheric pressure and temperature) are used for two-point calibration. The instrument automatically applies pressure compensation using its built-in barometer.
Can the Pro20i measure DO in high-salinity seawater?
Yes—salinity compensation is programmable from 0 to 70 ppt, and the polarographic sensor maintains accuracy across the full range when calibrated in situ or with appropriate salinity-adjusted standards.
Is the DO probe compatible with other YSI platforms?
No—the Pro20i uses a proprietary 6-pin connector and firmware-matched probe assembly; probes are not interchangeable with older ProODO or newer EXO series instruments.
How often should the DO membrane be replaced?
Typical membrane service life is 2–4 weeks under continuous field use; replacement frequency increases in high-fouling environments (e.g., wastewater, algae-rich ponds) or after exposure to solvents or oils.
Does the Pro20i support external GPS or depth sensors?
No—this model operates as a standalone handheld unit without expansion ports or Bluetooth/WiFi connectivity. For multi-parameter profiling, consider the YSI EXO2 platform with integrated GPS and depth modules.