Pool Link 500 Series, Optical Flow Switch (PI)

The Pool Link 500 Series Optical Flow Switch (PI) (Pool Link / Link Automation) is a solid-state, non-invasive electro-optical safety interlock engineered for the Pool Link 500 and 501 Series commercial water chemistry automation systems. Incorporating an industrial photo-interrupter (PI) or infrared/visible optoelectronic detection module, it monitors sample bypass velocity without placing mechanical paddles, shuttles, or delicate bearings in direct contact with the flowing water.

Acting as the system's primary safety interlock, it verifies water circulation across analytical probes and immediately commands the controller to de-energize chemical feed outputs (liquid chlorine feeders, acid metering pumps, and $CO_2$ solenoids) if the bypass flow stalls or drops below the critical threshold.

Hardware Architecture & Optoelectronic Dynamics

Designed to eliminate the mechanical binding, scaling, and pin wear common to wet-contact switches in high-bather commercial natatoriums and waterparks:

• Non-Invasive Optical Detection: Utilizes an integrated infrared (IR) LED emitter paired with a matched phototransistor receiver positioned on opposite sides of a clear optical sight-tube or machined acrylic flow channel.

• Optical Sensing Mechanisms (Model-Dependent):

  • Refractive Stream Detection: Senses the change in light refraction index between an air-filled dry tube and a full, laminar water stream.

  • Floating Optical Target / Flag: Monitors an internal, free-floating high-contrast opaque polymer bead or disk suspended in the clear vertical barrel. Dynamic water velocity elevates the target past the IR beam; loss of flow allows the target to settle below the optical axis, breaking the beam.

• Fouling-Resistant Solid-State Operation: Eliminates rotating shafts, mechanical pivots, and spring assemblies that easily jam from hair, lint, suspended body oils, or calcium carbonate scale in commercial pools.

• Integrated Signal Conditioning: Features an encapsulated miniature PCB containing threshold comparators and an output driver (open-collector or miniature dry-contact relay) that filters out optical flicker, air-bubble noise, and ambient light interference.

• Local Visual Status Indicator: Outfitted with an external bi-color or solid status LED on the sensor housing (typically Green = Flow Active / Interlock Closed, Red/Dark = No Flow / Locked Out), allowing instant verification during equipment room rounds.

Technical Specifications

• Compatible Controllers: Pool Link 501, Pool Link 500 Series, and Link Automation commercial controllers with active dry-contact or low-voltage DC flow interlock inputs.

• Output Configuration:

  • Isolated SPST dry contact (Normally Open - NO, closes upon verified flow).

  • Rated for low-voltage signal circuits: Max 24V AC/DC, 0.5A.

• Operating Power Requirement: 5V to 24V DC auxiliary input supplied directly by the Pool Link 501 mainboard accessory header.

• Hydraulic Actuation Limits:

  • Cut-In (Flow OK): Typically 0.35 to 0.50 GPM (approx. 1.3 to 1.9 LPM).

  • Cut-Out (No Flow): Drops out below 0.25 to 0.30 GPM (approx. 0.95 to 1.1 LPM).

• Maximum Working Pressure: 50 PSI (approx. 3.45 bar) within standard cast acrylic bypass flow cells.

• Operating Water Temperature: 32°F to 120°F (0°C to 49°C).

• Process Fitting: Integrated directly into the Pool Link 500 Series acrylic sight barrel or plumbed inline via standard 1/4" NPT or 1/2" NPT compression adapters.

• Wiring Interface: Standard 10-foot (approx. 3.0 m) factory-jacketed 3-wire or 4-wire shielded instrumentation cable (Power, Common/Ground, Signal/Switch).

Maintenance, Cleaning & Alignment Protocols

• Optical Barrel Scaling: Over time, high total dissolved solids (TDS) or elevated calcium hardness can form a hazy carbonate film on the inside walls of the clear sight tube, attenuating the IR beam and triggering false "NO FLOW" alarms.

• Routine Descaling: Isolate the bypass loop using the inlet/outlet petcocks. Unthread the optical barrel assembly and soak the clear tube in a 5% to 10% muriatic acid solution or white vinegar for 5 to 10 minutes to dissolve mineral clouding. Rinse with fresh water; do not use abrasive pads on the optical acrylic.

• Shielding from Ambient Light: While filtered for infrared frequencies, avoid pointing high-intensity halogen or unshielded UV work lights directly at the sensor's optical barrel during equipment room maintenance, as strong external light can occasionally saturate the phototransistor.