Professional 3-in-1 waterproof tester for simultaneous pH, ORP, and temperature measurements. The Hanna HI98121 delivers laboratory-grade accuracy with 0.01 pH resolution, ±0.05 pH accuracy, and ±2 mV ORP precision, featuring a replaceable pH electrode, automatic temperature compensation, and a floating design—making it the ideal choice for pool monitoring, sanitizer verification, wastewater treatment, and industrial applications.
Key Features & Benefits
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3-in-1 combo meter – Measures pH, ORP (oxidation-reduction potential), and temperature simultaneously
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High precision – 0.01 pH resolution with ±0.05 pH accuracy, ±2 mV ORP accuracy
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Waterproof & floats – IP67 rated, designed to float for easy retrieval if dropped in water
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Replaceable pH electrode – HI73127 electrode extends tester life indefinitely
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Auto calibration – One or two-point pH calibration with dual buffer sets
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Temperature compensation – Automatic ATC for accurate pH readings at any temperature
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HOLD feature – Freezes reading on display for easy recording
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Factory-calibrated ORP – Fixed platinum ORP sensor, ready to use
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Complete kit – Includes electrodes, buffers, ORP test solution, cleaning solution, and batteries
Why Measure Both pH and ORP?
The HI98121 allows you to monitor both pH and ORP simultaneously, providing a complete picture of water chemistry. This dual measurement capability is essential for:
Swimming Pool & Spa Monitoring
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pH: Ensures water balance for swimmer comfort and equipment protection (ideal 7.2-7.8)
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ORP: Verifies sanitizer effectiveness and disinfection potential (ideal 650-750 mV for pools)
- Together, pH and ORP provide complete water quality assessment
Food Sanitization
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pH: Monitors cleaning solution acidity/alkalinity
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ORP: Confirms sanitizer strength and effectiveness for food safety compliance
- Critical for HACCP programs and health department requirements
Wastewater Treatment
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pH: Ensures proper treatment process conditions
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ORP: Monitors oxidation/reduction reactions and treatment effectiveness
- Optimizes chemical dosing and process control
Industrial Applications
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Plating operations: pH and ORP control for consistent plating quality
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Cooling towers: Corrosion and scale prevention through pH/ORP monitoring
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Chemical processing: Redox reaction monitoring and process optimization
Understanding ORP (Oxidation-Reduction Potential)
Similar to pH measurement that quantifies how acidic or alkaline solutions are, ORP measurements quantify the overall state of a solution as having the ability to oxidize or reduce chemical species. ORP is measured in millivolts (mV):
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Positive ORP values: Indicate oxidizing conditions (chlorine, ozone, hydrogen peroxide)
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Negative ORP values: Indicate reducing conditions (antioxidants, reducing agents)
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Higher ORP in pools: Indicates stronger sanitizer effectiveness and better disinfection
The HI98121 uses a platinum ORP sensor—a noble metal that is chemically inert and promotes rapid electron exchange for accurate, stable ORP measurements.
Advanced Features for Professional Use
Waterproof & Floating Design
IP67 waterproof rating protects against water immersion, while the floating design ensures that if you accidentally drop the tester in a pool, tank, or water body, it won't sink—simply retrieve it from the surface and continue testing.
Replaceable HI73127 pH Electrode
The included HI73127 pH electrode features:
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Extractable cloth junction: Can be renewed by pulling out to expose fresh material
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Glass body: Chemically resistant and quick to reach thermal equilibrium
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Easy replacement: Simple screw-on design when replacement is needed
- Extends tester life indefinitely—replace electrode instead of entire meter
Fixed Platinum ORP Sensor
The built-in ORP sensor uses pure platinum for optimal performance:
- Factory calibrated for immediate use
- High exchange current density for rapid response
- Chemically inert—won't oxidize or reduce
- Durable construction for long-term reliability
Automatic Temperature Compensation (ATC)
Built-in temperature sensor provides automatic temperature compensation for pH readings, ensuring accuracy across the temperature range of -5.0 to 60.0°C (23.0 to 140.0°F). Temperature is displayed simultaneously with pH and ORP.
Flexible pH Calibration
Automatic one or two-point calibration with two selectable buffer sets:
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Buffer Set 1: pH 4.01, 7.01, 10.01
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Buffer Set 2: pH 4.01, 6.86, 9.18
Choose the buffer set that best matches your application requirements.
HOLD Feature
The HOLD button freezes the reading on the display, making it easy to record measurements in challenging environments or when you need to document results.
Lightweight & Ergonomic Design
At just 100g (3.5 oz), the HI98121 is lightweight and ergonomically designed for comfortable handheld use. The compact size (163 × 40 × 26 mm) makes it easy to carry and use anywhere.
Applications
- Swimming pools and spas (pH and chlorine monitoring)
- Aquariums and aquaculture (water quality management)
- Food and beverage sanitization (HACCP compliance)
- Wastewater treatment (process monitoring and control)
- Cooling tower water treatment (corrosion prevention)
- Plating operations (bath monitoring)
- Industrial process control (redox reactions)
- Environmental monitoring (water quality assessment)
- Laboratory and research (general pH/ORP testing)
Complete Kit - Ready to Test
The HI98121 arrives with everything needed for immediate pH and ORP testing:
- HI98121 pH/ORP/Temperature tester with floating design
- HI73127 replaceable pH electrode
- HI73128 electrode removal tool
- pH 4.01 buffer solution sachet (20 mL)
- pH 7.01 buffer solution sachet (20 mL)
- HI70022 470 mV ORP test solution sachets (2 × 20 mL)
- HI70300N storage solution sachet (20 mL)
- HI700601 electrode cleaning solution sachet (20 mL)
- 1.5V AAA batteries (4 pcs.)
- Instrument quality certificate
- Instruction manual
Technical Specifications
| Specification |
Detail |
| SKU |
HI98121 |
| pH Range |
-2.00 to 16.00 pH |
| pH Resolution |
0.01 pH |
| pH Accuracy (@25°C/77°F) |
±0.05 pH |
| pH Calibration |
Automatic, one or two-point with two buffer sets (pH 4.01/7.01/10.01 or 4.01/6.86/9.18) |
| pH Temperature Compensation |
Automatic (ATC) |
| ORP Range |
±1000 mV |
| ORP Resolution |
1 mV |
| ORP Accuracy |
±2 mV |
| ORP Calibration |
Factory calibrated |
| Temperature Range |
-5.0 to 60.0°C / 23.0 to 140.0°F |
| Temperature Resolution |
0.1°C / 0.1°F |
| Temperature Accuracy |
±0.5°C / ±1°F |
| pH Electrode |
HI73127 replaceable pH electrode (included) |
| ORP Electrode |
Fixed platinum ORP sensor |
| Waterproof Rating |
IP67 (waterproof and floats) |
| Automatic Shut-Off |
Auto-off after 8 minutes of non-use |
| Battery Type / Life |
1.5V AAA (4) / Approximately 250 hours continuous use |
| Environment |
-5 to 50°C (23 to 122°F); RH max 100% |
| Dimensions |
163 × 40 × 26 mm (6.4 × 1.6 × 1.0") |
| Weight |
100 g (3.5 oz.) |
Typical ORP Values by Application
Swimming Pools
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Ideal range: 650-750 mV (indicates effective chlorine sanitization)
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Minimum: 650 mV (health department requirement in many jurisdictions)
- Higher ORP = better disinfection and pathogen control
Drinking Water
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Typical range: 200-400 mV (chlorinated municipal water)
- Positive ORP indicates oxidizing disinfectants present
Wastewater Treatment
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Aerobic treatment: +100 to +400 mV (oxidizing conditions)
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Anaerobic treatment: -100 to -300 mV (reducing conditions)
Replacement Parts & Accessories
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HI73127: Replacement pH electrode
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HI70004P: pH 4.01 buffer solution
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HI70007P: pH 7.01 buffer solution
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HI70010P: pH 10.01 buffer solution
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HI70022: 470 mV ORP test solution
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HI70300: Storage solution for pH & ORP electrodes
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HI700601: Electrode cleaning solution
Why Choose the HI98121?
The HI98121 is the only waterproof, floating combo meter in its class that measures pH, ORP, and temperature simultaneously. The replaceable pH electrode design protects your investment, while the factory-calibrated platinum ORP sensor ensures accurate oxidation-reduction measurements right out of the box. Whether you're a pool professional, food safety manager, wastewater operator, or industrial technician, the HI98121 delivers the accuracy, reliability, and convenience you need.
Economical Professional Solution
Get professional-grade accuracy for both pH and ORP in a single, affordable meter. The HI98121 eliminates the need to purchase separate pH and ORP meters, saving you money while providing comprehensive water chemistry monitoring.
Warranty & Support
The HI98121 pH/ORP/Temperature Tester is backed by Hanna's quality guarantee and customer support. For technical assistance, calibration questions, or replacement parts, our expert team is ready to help.
