An online pH controller combines a pH/ORP electrode with a 96 × 96 mm panel controller to measure pH 0 – 14 and ORP ±1200 mV continuously, with automatic temperature compensation, 4–20 mA output, alarm relays and RS485 Modbus. It serves water and wastewater treatment, boiler water, food and chemicals – following European practice under IEC 60746-2 and EN 61326-1.
pH controller specifications
| Parameter | Value |
|---|---|
| Range | pH: 0.00 – 14.00 pH; ORP: −1200 … +1200 mV |
| Accuracy | pH: ±0.1 pH; ORP: ±2 mV |
| Temperature compensation | 0 – 100 °C, manual / automatic (Pt1000, Pt100, NTC 10k) |
| Sensor operating temperature | 0 – 60 °C (standard); 0 – 100 °C (high-temperature sensor) |
| Sensor | 2/3-in-1 combination pH electrode, ORP electrode |
| Calibration | 3-point: pH 4.00; 6.86; 9.18 |
| Display | 128 × 64 dot-matrix LCD |
| Analog output | Isolated, reversible 4–20 mA, max load 750 Ω |
| Control output | 2 high/low alarm relays, NO contacts 3 A / 250 VAC |
| Communication | RS485 Modbus, 2400 / 4800 / 9600 baud |
| Supply | 220 VAC ±10 %, 50/60 Hz (standard); 110 VAC, 24 VDC, 12 VDC (optional) |
| Protection | IP65 |
| Controller ambient | 0 – 70 °C, RH ≤ 95 % |
| Size / cut-out | 96 × 96 × 130 mm / 92 × 92 mm, panel mount |
How pH measurement works
A glass electrode produces a potential proportional to pH according to the Nernst equation: the theoretical slope is 59.16 mV/pH at 25 °C and changes with temperature, so compensation with Pt100/Pt1000/NTC is needed. A healthy electrode shows a 92 – 102 % slope and an offset within ±30 mV at pH 7 (Thermo Fisher – pH Measurement Handbook). Calibrate at three points with pH 4.00, 6.86 and 9.18 buffers bracketing the sample.
Online pH measurement and control with the pH controller
- Isolated 4–20 mA to PLC/SCADA for logging and control.
- 2 high/low relays drive acid/alkali dosing pumps or alarms.
- RS485 Modbus to HMI or BMS.
Applications
- Boiler water: pH 10.5 – 12.0 in the boiler and > 9.2 in feedwater per EN 12953-10 – combine with boiler TDS control.
- Feedwater treatment, RO, cooling water and towers.
- Wastewater neutralisation; ORP for cyanide and chromium treatment and chlorine disinfection.
- Food, beverage, pharmaceuticals, plating, chemicals.
Calibration and electrode care
- Use fresh buffers at sample temperature; rinse with distilled water between buffers.
- Do not wipe the glass bulb; blot gently.
- Never let the electrode dry; store it in storage solution.
- Clean deposits in 0.1 M HCl for about 15 minutes; replace the electrode when the slope falls below 92 %.
Reference standards
| Standard | Scope |
|---|---|
| IEC 60746-2 | Performance of electrochemical analysers – pH |
| DIN 19266 | pH reference buffer solutions |
| EN 61326-1 | EMC |
| EN 60529 | IP65 protection |
| EN 12953-10 | Boiler feedwater and boiler water pH |
Related products
Contact ISE
EQUIPMENT INDUSTRIAL SOLUTION CO., LTD (ISE) – Ho Chi Minh City, Vietnam.
Contact us: Sales +84 909 617 185 – Technical +84 979 117 185 – Email: [email protected]
