Lab-grade pH measurement purpose-built for RO, distilled, and deionized water — in a field-ready, IP57-rated body.
The Apera PH850-PW (AI5541) is a portable pH meter engineered specifically for low ion-concentration water sources — RO, drinking, distilled, and deionized water — where standard pH electrodes routinely produce slow, drifting, or unreliable readings. Equipped with the Swiss LabSen® 803 3-in-1 glass pH/temperature electrode, it delivers fully stabilized readings in 30–60 seconds with ±0.01 pH accuracy across the full 0–14 pH range.
Most pH meters ship with electrodes optimized for nutrient-rich, high-conductivity solutions. Put those probes into RO water, DI water, or any low ion-concentration feed and you get sluggish response, unstable readings, and calibration drift — because the reference junction can't maintain adequate electrolyte flow in a nearly ion-free environment.
The Apera PH850-PW (SKU AI5541) is built around that exact problem. Its Swiss-engineered LabSen 803 electrode uses an ultra-low-resistance L-type cylindrical glass membrane (under 50 MΩ) specifically formulated to generate accurate, stable signals in purified water. The moveable sleeve junction allows users to dial in electrolyte infiltration rate to match the ion concentration of the sample — a control that standard fixed-junction electrodes simply don't offer. The result: stabilized readings in 30–60 seconds, even in near-zero-conductivity water.
Any licensed cannabis or hemp cultivation facility running reverse osmosis as the foundation of their water program needs a meter that can accurately read that RO baseline — before nutrients are added. A standard pH pen will drift or read incorrectly in RO water, giving you a false starting point that throws off your entire feed calculation.
The PH850-PW is the right tool at the pre-mix stage: verify RO output pH, check distilled or deionized source water, and validate your water treatment system is performing to spec. It's also well-suited for water quality compliance checks in facilities where source-water documentation is part of state licensing requirements. The foldable stand doubles the unit as a benchtop instrument for lab workstations, while the IP57 waterproof rating and silicone grip case make it equally practical on the grow floor or in the mechanical room.
The included LabSen 803 is a 3-in-1 glass electrode combining pH measurement, ORP capability (with a separate ORP probe), and integrated temperature sensing in one body. Its Swiss-patented pH/temperature combination structure places the temperature element in an independent cavity directly beneath the glass membrane, with a built-in heat-conducting medium that increases temperature response speed by 40% compared to a conventional isolated thermistor — which directly accelerates automatic temperature compensation (ATC) and shortens overall stabilization time.
The silver ion trap reference system adds an additional layer of junction protection. On top of the standard long-life reference, the trap absorbs exuded Ag⁺ ions to prevent junction clogging in samples that contain sulfides or proteins — common in certain nutrient formulas. Apera's proprietary blue gel inner solution is non-flowing, which eliminates air bubble formation inside the glass membrane and removes a common source of measurement instability. The cylindrical glass membrane is also significantly more impact-resistant than traditional glass bulb designs.
The PH850-PW meter body offers 1–3 point automatic calibration, automatically recognizing five standard buffer solutions (pH 1.68, 4.00, 7.00, 10.01, and 12.45) across both USA and NIST series. After a two- or three-point calibration, the meter displays electrode slope — a direct indicator of probe condition that tells you when the LabSen 803 needs maintenance or replacement, before it starts affecting data quality.
Intelligent self-diagnosis flags out-of-range values, electrode invalidation, and incorrect calibration in real time. Auto-hold locks the reading when the measurement stabilizes, and auto power-off preserves battery life during busy production days. Power comes from 3 AA batteries, keeping the meter operational without proprietary charging infrastructure. The standard BNC connector means the PH850-PW body is also compatible with other Apera LabSen-series electrodes if you expand into general water solutions or ORP measurement. Warranty coverage is 3 years on the meter body and 6 months on the LabSen 803 electrode.
| SKU | AI5541 / PH850-PW |
| pH Range | 0–14 pH |
| pH Accuracy | ±0.01 pH |
| Temperature Range | 0–80°C (32–176°F) |
| Electrode | Swiss LabSen 803 3-in-1 Glass pH/Temp. Electrode |
| Electrode Glass Membrane Resistance | <50 MΩ (ultra-low resistance, L-type cylindrical) |
| Stabilization Time (RO/DI Water) | 30–60 seconds (fully stabilized) |
| Calibration | 1–3 point auto-calibration; recognizes pH 1.68, 4.00, 7.00, 10.01, 12.45 |
| Waterproof Rating | IP57 |
| Power | 3 × AA batteries |
| Connector | Standard BNC (pH) + RCA (temperature) |
| Warranty | 3 years (meter body) / 6 months (LabSen 803 electrode) |
Standard pH electrodes rely on sufficient ion concentration in the sample to maintain stable reference junction potential. In RO, distilled, or deionized water — which are extremely low in dissolved ions — a standard probe produces slow drift, erratic readings, and unreliable calibration. The LabSen 803 electrode in the PH850-PW uses an ultra-low-resistance glass membrane (<50 MΩ) and a moveable sleeve junction specifically engineered to generate stable signals in these low-conductivity environments, reaching stabilized readings in 30–60 seconds.
Yes. The PH850-PW and LabSen 803 electrode are designed primarily for purified water and low ion-concentration solutions, but Apera confirms they are also suitable for general water solutions. The meter covers the full 0–14 pH range with ±0.01 accuracy. For facilities measuring both RO source water and mixed nutrient solution, this single unit can handle both.
The PH850-PW meter body supports ORP measurement in mV mode, but an ORP probe (such as Apera's 301Pt-C, sold separately) is required. The included LabSen 803 is a pH/temperature electrode only.
After completing a 2- or 3-point calibration, the PH850-PW displays the electrode slope value on screen. Slope is the most direct indicator of electrode condition — a significant deviation from the expected 95–105% range signals that the probe is degrading. The built-in self-diagnosis function will also flag electrode invalidation when calibration is no longer achievable within acceptable parameters.
The meter runs on 3 AA batteries — no proprietary charging required. It includes a foldable stand that allows the unit to function as a benchtop meter on a workbench or lab station, in addition to standard handheld field use.
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