Pool Link 500 Series, Amperometric FAC PPM Probe (0-20ppm)

The Pool Link 500 Series Amperometric Free Available Chlorine (FAC) PPM Probe (0–20 PPM) (Pool Link / Link Automation) is a commercial-grade electrochemical sensor designed for continuous, direct quantification of free chlorine residual in commercial aquatic facilities, waterparks, splash pads, and municipal pools.

Operating on amperometric principles, it measures the electrical current generated by the reduction of hypochlorous acid ($\text{HOCl}$) and hypochlorite ions ($\text{OCl}^-$) at a working electrode surface, providing real-time concentration readouts in parts-per-million ($\text{PPM}$ or $\text{mg/L}$) independent of cyanuric acid interference. The expanded 0–20 PPM range accommodates high-demand recreational water venues requiring elevated disinfectant thresholds or automated shock/breakpoint chlorination tracking.

Hardware & Analytical Architecture

Engineered for continuous immersion in dynamic bypass flow loops across high-turnover natatorium and waterpark environments:

• Micro-Porous Membrane Assembly: Utilizes a replaceable, electrolyte-filled membrane cap (typically microporous PTFE, PVDF, or composite polymer). The selective membrane allows dissolved hypochlorous acid molecules to diffuse through to the internal electrode while preventing bather organics, oils, suspended solids, and scale from coating the working electrode surface.

• Working & Counter/Reference Electrode Pair: Features an internal gold ($\text{Au}$) or platinum ($\text{Pt}$) working cathode where chemical reduction occurs, paired with a silver/silver chloride ($\text{Ag/AgCl}$) reference anode in a specialized, pre-buffered internal gel electrolyte reservoir.

• Expanded Dynamic Range (0–20.00 PPM): Calibrated to maintain linearity well beyond standard recreational bands ($1.0–5.0\text{ PPM}$), allowing uninterrupted monitoring through secondary shock dosing, waterpark wave pools, and hyper-chlorinated municipal splash pads.

• Signal Conditioning Electronics: Houses an encapsulated internal pre-amplifier that converts low nanoampere-level reduction currents into a stable, low-noise analog voltage or digital signal transmitted directly to the Pool Link 501 controller board.

• Flow-Dependent Diffusion Chamber: Designed specifically to mount inside the Pool Link 500 Series machined acrylic bypass flow cell manifold, ensuring consistent laminar flow velocity across the membrane face.

Technical Specifications

• Measurement Range: 0.00 to 20.00 PPM (mg/L) Free Available Chlorine (FAC).

• Resolution: 0.01 PPM ($0.00–9.99\text{ PPM}$); 0.1 PPM ($10.0–20.0\text{ PPM}$).

• Operating pH Dependency: Operates optimally between pH 6.80 and 8.00 (calibrated via the controller's integrated pH sensor for automated hypochlorous acid dissociation curve compensation).

• Linearity & Accuracy: $\pm 2\%$ of full scale or $\pm 0.05\text{ PPM}$ (whichever is greater) under stable flow and temperature.

• Response Time ($T_{90}$): Typically reaches $90\%$ of reading within 15 to 30 seconds after sample chlorine concentration shifts.

• Sample Stream Flow Requirements: Requires a constant bypass velocity of 0.5 to 1.5 GPM (approx. 1.9 to 5.7 LPM) within the acrylic flow cell to prevent sample starvation at the membrane boundary.

• Operating Temperature Range: 35°F to 120°F (2°C to 49°C).

• Maximum Hydraulic Pressure: 50 PSI (approx. 3.45 bar) in closed acrylic flow manifolds.

• Process Fitting: 1" or 3/4" NPT threaded body / compression collar gland mount matched to the Pool Link 500 Series multi-port acrylic chamber.

• Cable Configuration: Standard 10-foot (approx. 3.0 m) factory-shielded, low-noise multi-conductor lead (terminated with a keyed CONX water-tight circular plug or labeled PCB terminal pins).

Commissioning, Calibration & Electrolyte Maintenance

         Bypass Flow In (Laminar, 0.5–1.5 GPM)
                         │
                         ▼
        ┌───────────────────────────────────┐
        │       Probe Body / Pre-Amp        │
        │  ┌─────────────────────────────┐  │
        │  │ Internal Buffer Electrolyte │  │
        │  │       (Ag/AgCl Anode)       │  │
        │  └──────────────┬──────────────┘  │
        │                 │                 │
        │          Working Cathode          │
        │         (Gold / Platinum)         │
        └─────────────────┬─────────────────┘
                          ▼
            [ Selective Membrane Cap ]
                          ▲
                          │
          Continuous Diffusion of HOCl/OCl⁻

• Polarization Period (Burn-In): When newly installed or refilled with fresh electrolyte, the probe requires 1 to 2 hours of continuous electrical polarization under steady bypass flow before zero-point and span calibration can occur.

• Zero & Span Calibration:

  • Zero Reference: Calibrated in dechlorinated water (or by using the controller's software zero offset).

  • Span Calibration: Performed using a calibrated primary colorimeter or DPD-1 photometer test taken directly from the petcock sampling valve while the pool is at normal operational setpoint ($2.0–5.0\text{ PPM}$).

• Electrolyte & Membrane Replacement Interval: The internal gel electrolyte and membrane cap should be serviced every 6 to 12 months, or sooner if response times become sluggish or readings drift erratic due to calcification or bio-film fouling.