The pH-Rx from Etatron D.S. (Italy) is an integrated measurement-and-dosing control system that combines a pH and Redox (ORP) analyzer with a chemical metering pump in a single wall-mounted unit. Rather than requiring separate instruments for measurement, control, and chemical injection — with the wiring, calibration, and interoperability issues that introduces — the pH-Rx reads the process value directly from a pH and Redox electrode pair and drives the dosing pump proportionally to maintain the setpoint. This architecture is the workhorse of water treatment in cooling towers, swimming pools, electroplating baths, wastewater neutralization, and food & beverage CIP systems.

How does the proportional PWM dosing control work?

In ON/OFF mode, the pump runs at full stroke frequency whenever the measured value exceeds the setpoint plus hysteresis, then stops when it drops below the setpoint — simple but prone to overshoot. In proportional PWM mode, the controller modulates the pump's stroke frequency in inverse proportion to the deviation from setpoint: near setpoint, the pump strokes slowly (minimizing overshoot); far from setpoint, it strokes at maximum frequency (120 or 150 strokes/min depending on model) for rapid correction. The setpoint, hysteresis band, proportional band, and maximum dosing time (over-dosing alarm) are all configurable via the backlit LCD and membrane keypad. A PT100 temperature sensor input provides automatic temperature compensation — essential for accurate pH measurement where electrode slope varies with temperature per the Nernst equation (0.198 mV/pH/°C at 25°C).

What pump configurations are available in the pH-Rx family?

The DLX pH-Rx uses a solenoid-driven diaphragm pump with PVDF body, PTFE diaphragm, ceramic check balls, and FPM (Viton) seals — compatible with acids, bases, and oxidizing agents — delivering 1 to 20 l/h at up to 20 bar. The DLXB variant adds a mechanical stroke-length adjuster (20–100%) for finer flow trimming without changing stroke frequency. The eTwin pH-Rx packages two independent peristaltic pump heads with two parameter controllers in one IP65 enclosure — typically pH control on one channel and chlorine or Redox on the other — for compact dual-parameter water treatment in a single wall-mounted instrument.