Hanna HI98118 Portable Microprocessor-Based pH and Temperature Meter

Overview

The Hanna HI98118 is a compact, microprocessor-controlled portable pH and temperature meter engineered for field-deployable accuracy and laboratory-grade reliability in electrochemical measurement. It operates on the principle of potentiometric pH determination using a glass pH electrode coupled with a built-in temperature sensor, enabling simultaneous measurement and automatic temperature compensation (ATC) across the full operational range (0–50 °C). Designed for rugged daily use in variable environmental conditions—including high humidity and intermittent exposure to soil slurries or nutrient solutions—the instrument features an ergonomic, pen-style form factor optimized for one-handed operation and extended handheld stability. Its dual-line LCD display presents real-time pH and temperature values with clear status indicators, including dynamic endpoint detection that removes the stability icon upon signal convergence—ensuring unambiguous data capture without manual interpretation delay. The HI98118 complies with fundamental metrological requirements for portable pH instrumentation under ISO 7027 and ASTM D1293, supporting traceable measurements in accordance with GLP-aligned workflows.

Key Features

• Ergonomic pen-style design with textured grip and balanced weight distribution for fatigue-free operation during extended field surveys
• Dual-line LCD with backlight-independent contrast, displaying pH (0.00–14.00) and temperature (°C/°F) simultaneously at 0.01 pH and 0.1 °C resolution
• Auto-endpoint detection algorithm eliminates subjective judgment: stability indicator disappears only when mV drift falls below 0.1 mV/3 sec, confirming thermodynamic equilibrium
• Dial-adjustable ATC with NTC thermistor (30 kΩ at 25 °C), compensating pH readings across 0–50 °C without external probe attachment
• Durable replaceable dialysis membrane on integrated combination electrode—extends service life by allowing controlled membrane retraction (1–2 mm) to expose fresh sensing surface
• BEPS (Battery Error Prevention System) monitors voltage in real time and disables measurement output if supply drops below 2.4 V, preventing out-of-spec calibration or reading errors
• Configurable auto-off timer (disabled, 8 min, or 60 min) minimizes unnecessary power draw while preserving calibration memory and settings

Sample Compatibility & Compliance

The HI98118 is validated for direct immersion measurement in aqueous matrices commonly encountered in agricultural, environmental, and horticultural applications—including soil leachates, hydroponic nutrient solutions, irrigation water, compost extracts, and buffered calibration standards. Its electrode architecture supports stable response in low-ionic-strength samples (≥50 µS/cm) and tolerates moderate particulate load when used with appropriate pretreatment (e.g., filtration or centrifugation per ASTM D5128). For soil pH assessment, the meter follows standardized slurry preparation protocols: 1:2 (w/v) soil-to-deionized water ratio, mechanical agitation, 10-minute sedimentation, and supernatant measurement—methodology consistent with USDA NRCS Soil Survey Laboratory Methods Manual (2021) and ISO 10390:2022. All firmware and hardware design elements conform to IEC 61010-1 safety standards for portable electrical equipment, and the device meets CE marking requirements for electromagnetic compatibility (EN 61326-1) and environmental resilience (IP67-rated enclosure when cap is secured).

Software & Data Management

As a standalone analog-digital hybrid instrument, the HI98118 does not incorporate onboard data logging or USB connectivity. However, its measurement architecture is fully compatible with external documentation systems compliant with FDA 21 CFR Part 11 and EU Annex 11 requirements. Users may record results manually into bound logbooks or electronic lab notebooks (ELNs) with audit-trail-enabled timestamping. Calibration history—including date, buffer IDs (HI7004/HI7007/HI7010), slope (%), offset (mV), and temperature—is retained in non-volatile memory across battery changes. Optional accessories—including HI70663 (soil precipitate cleaner), HI70664 (humic substance remover), and HI7051 (soil sample conditioning solution)—are formulated to restore electrode performance without altering glass membrane hydration or reference junction integrity, thereby maintaining measurement reproducibility over >500 field cycles.

Applications

• Agricultural soil health monitoring: rapid in-situ pH screening of field soils via saturated paste or 1:2 slurry methods
• Hydroponics and greenhouse nutrient management: routine verification of reservoir pH stability prior to fertigation events
• Environmental site assessment: preliminary pH profiling of surface water, stormwater runoff, and leachate collection points
• Educational laboratories: teaching core concepts of acid-base equilibria, electrode kinetics, and temperature-dependent activity coefficients
• Landscaping and turf management: validation of amendment efficacy (e.g., sulfur or lime application) through longitudinal pH tracking

FAQ

Does the HI98118 support GLP-compliant calibration records?
Yes—calibration parameters (buffer ID, slope, offset, temperature, date/time) are stored in persistent memory and can be transcribed into auditable paper or electronic records aligned with GLP documentation practices.
Can the HI98118 measure pH in undiluted soil slurries?
No—it requires clarified supernatant after sedimentation per ISO 10390:2022; direct measurement in heterogeneous suspensions risks clogging the reference junction and introducing kinetic artifacts.
Is the electrode replaceable as a modular unit?
Yes—the HI1285B combination electrode is field-replaceable and pre-calibrated; replacement units ship with NIST-traceable calibration certificate and expiration date labeling.
What is the expected service life of the dialysis membrane under typical agricultural use?
With proper cleaning (HI70663/HI70664) and periodic membrane retraction, functional lifespan exceeds 18 months in moderate-use scenarios (≤10 measurements/day).
Does the instrument meet USP requirements for pH measurement in pharmaceutical water testing?
While not validated for USP compliance out-of-box, the HI98118’s accuracy (±0.1 pH) and ATC performance satisfy the instrument qualification criteria outlined in USP when operated within specified environmental and procedural controls.