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

The Pool Link 500 Series Amperometric Total Available Chlorine (TAC) PPM Probe (0–20 PPM) (Pool Link / Link Automation) is a specialized commercial-grade electrochemical sensor engineered for continuous, real-time quantification of Total Chlorine residual in municipal aquatic facilities, indoor competitive natatoriums, waterparks, and commercial spas.

Unlike Free Available Chlorine (FAC) probes that selectively measure hypochlorous acid ($\text{HOCl}$) and hypochlorite ($\text{OCl}^-$), the TAC probe incorporates an internal catalytic or iodide-supplemented reagent electrolyte behind its microporous membrane. This reaction reduces both free chlorine and combined chlorine species—chloramines such as monochloramine, dichloramine, and nitrogen trichloride—converting them into a measurable reduction current scaled directly to parts-per-million ($\text{PPM}$ or $\text{mg/L}$) Total Chlorine. When paired with a matching 500 Series FAC probe, it allows the controller to compute real-time Combined Chlorine ($\text{TAC} - \text{FAC} = \text{Combined Chlorine}$) to automate UV systems, ozone destruction loops, or breakpoint shock dosing.

Hardware & Analytical Architecture

Engineered for continuous immersion in dynamic bypass flow loops across high-bather-load commercial environments:

• Catalytic Total Chlorine Reaction Matrix: Employs a specialized membrane-covered electrolyte cell containing a potassium iodide ($\text{KI}$) buffer system. Chloramines and free chlorine diffuse through the membrane and oxidize iodide ions into triiodide ($\text{I}_3^-$), which is electrochemically reduced at the working electrode, generating a current proportional to Total Chlorine concentration.

• Micro-Porous Polymer Membrane Cap: Features a precision microporous PTFE or PVDF membrane assembly designed to protect the internal working electrode from bather organics, body oils, cyanuric acid, and calcium scale while regulating diffusion rates.

• Electrode Configuration: Contains a noble metal cathode (typically platinum or gold) where chemical reduction takes place, paired with an integrated silver/silver chloride ($\text{Ag/AgCl}$) reference anode submerged in the buffered electrolyte reservoir.

• Expanded Dynamic Range (0–20.00 PPM): Broad measurement window covers standard operational ranges ($1.0–5.0\text{ PPM}$) as well as elevated thresholds required for secondary disinfection loops, indoor chloramine management, and automated breakpoint hyper-chlorination cycles.

• Internal Pre-Amplifier Circuitry: Houses encapsulated signal-conditioning electronics within the upper body, translating nanoampere redox currents into a temperature-compensated, low-noise analog voltage or digital signal for the Pool Link 501 controller.

• Bypass Cell Compatibility: Direct mechanical fit for the Pool Link 500 Series machined acrylic multi-port bypass flow cell manifold.

Technical Specifications

• Measurement Parameter: Total Available Chlorine (TAC / Total Residual Chlorine).

• Measurement Range: 0.00 to 20.00 PPM (mg/L).

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

• Operating pH Dependency: Operates across pH 6.50 to 8.50 (best performance achieved when paired with the controller's active pH sensor for automatic algorithmic compensation).

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

• Response Time ($T_{90}$): Reaches $90\%$ of stabilized value within 60 to 120 seconds (TAC reaction dynamics are slightly slower than direct FAC reduction due to the internal iodide oxidation step).

• Sample Stream Flow Requirements: Requires a continuous bypass flow of 0.5 to 1.5 GPM (approx. 1.9 to 5.7 LPM) within the acrylic chamber to prevent boundary layer depletion at the membrane surface.

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

• Maximum Hydraulic Working Pressure: 50 PSI (approx. 3.45 bar).

• Process Fitting: 1" or 3/4" NPT external body threads / compression gland mount.

• Cable Lead: Standard 10-foot (approx. 3.0 m) factory-shielded, chemical-resistant multi-conductor cable terminated with a sealed CONX circular connector or stripped/tinned PCB terminal leads.

Commissioning, Calibration & Electrolyte Maintenance

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

• Polarization (Burn-In) Period: Upon initial installation or after electrolyte replenishment, the sensor requires 2 to 4 hours of continuous electrical polarization under steady bypass flow before zero-offset and span calibration can be finalized.

• Calibration Protocol:

  • Zero Calibration: Set in dechlorinated water or via controller zero-offset adjustment.

  • Span Calibration: Performed using a calibrated primary photometer or colorimeter test (Total Chlorine DPD-3 or DPD-4 reagent test) drawn directly from the probe chamber petcock while the recirculation system operates under normal bather loads.

• Electrolyte & Membrane Replacement: The internal catalytic iodide electrolyte and membrane cap require routine servicing every 3 to 6 months (or sooner under heavy bather and high-chloramine conditions), as internal reagents gradually deplete through continuous chemical consumption.