Digital ORP Probe with Platinum Ring Electrode and 1 inch NPT Thread for 2000 mV Range ORP Sensor Applications

The DRH790 digital ORP probe is the installation-flexible member of the DRH790 family: a φ35 mm ABS-bodied ORP sensor with a platinum ring electrode and a genuine 1" NPT thread at both ends, so the same probe can be fitted to a side-wall bracket, a top flange, a pipe tee, a submerged holder or a flow-through cell without adapters. The 100 mm insertion depth (115 mm including the cleaning connector) matches standard imperial fittings, which is what most plating lines, chemical skids and municipal plants already use.

The platinum ring is the key to long-term ORP stability. Unlike a glass pH bulb, the platinum surface is not affected by hydrofluoric acid or high-alkali conditions, and it responds to the oxidising or reducing power of the water rather than to acidity. The DRH790 therefore handles -2000 to +2000 mV with 1 mV resolution and ±2 mV accuracy, covering chromium reduction at strongly negative potentials as well as hypochlorite and ozone oxidation at strongly positive potentials.

Calibration supports zero-point, slope and deviation modes. Deviation calibration is particularly useful in plating and chemical service, where a small, stable offset often appears after the electrode has been in a bath for a few weeks: instead of replacing the probe, you measure a standard solution once, enter the deviation, and the reading is corrected on the spot. The ABS housing is sealed to IP68 for continuous immersion, and the PUR cable (10 m standard) resists oils, plating mist and UV, which PVC cable does not.

Electrically, the probe runs on 9 to 36 VDC at roughly 0.2 W, and power and communication are isolated inside the sensor body — an important detail in plating and electrochemical plants where stray currents and different earth potentials are normal. Data is delivered over RS485 Modbus RTU, so the ORP value and the sample temperature can be polled by a PLC, a multi-channel controller or a SCADA gateway, and several probes can share one bus by using different slave addresses.

1. Platinum ring electrode. The platinum sensing surface is chemically inert and unaffected by hydrofluoric acid or strong alkali, and it cleans back to a stable response far more easily than a coated glass membrane.
2. True 1" NPT thread at both ends. A genuine imperial thread with 100 mm insertion depth means the probe drops into standard tees, flanges and immersion holders without adapters or custom machining.
3. Five installation methods. Side-wall, top flange, pipeline, submerged and flow-through mounting are all supported by the same body, so one spare part covers every location in the plant.
4. ±2000 mV range, ±2 mV accuracy. Full oxidising and reducing coverage with enough precision to control reduction and oxidation reactions tightly.
5. Deviation calibration on site. Correct a stable offset with a single standard solution and one entry, avoiding unnecessary electrode replacement and downtime.
6. IP68 immersion-rated ABS body. Continuous submersion in tanks, sumps and channels, with a compact φ35 mm × 260 mm profile that fits congested skids.
7. PUR cable, 10 m standard. Polyurethane jacket resists oil, abrasion, plating mist and UV, and factory termination preserves the IP68 seal.
8. Isolated RS485 Modbus electronics. Internal isolation removes ground-loop error and lets the probe sit far from the controller on the same bus as other instruments.
9. Wide 9–36 VDC input. About 0.2 W consumption allows battery and solar operation for remote or temporary monitoring points.
10. Low maintenance footprint. Monthly visual check, monthly calibration verification and annual electrode replacement are enough to keep the probe in service.

• Electroplating and metal finishing: chromium reduction (hexavalent to trivalent), oxidising bath control, rinse water monitoring in acid and alkaline lines.
• Chemical process industry: oxidation and reduction reaction control, oxidant dosing, effluent oxidation state monitoring.
• Printed circuit board and electronics manufacturing: etching and oxidation bath supervision, rinse water quality.
• Printing and dyeing: oxidant control in bleaching and dye baths for consistent colour reproduction.
• Wastewater treatment: cyanide destruction, sulphide oxidation, disinfection control and industrial effluent compliance.
• Drinking water and purified water: chlorine and ozone disinfection residual verification.
• Food, beverage and pharmaceutical process water: CIP oxidant control and process water oxidation state monitoring.
• Cooling and circulating water: oxidant programme control for biofouling prevention.

The installation angle must be within ±30° of vertical; do not install the probe horizontally or upside down. Keep the protective cap fitted while the probe is being mounted and remove it only after the installation is complete. In plating and chemical baths, keep the platinum ring clear of heater elements and agitator blades, and allow at least one probe diameter of clearance from the tank wall to avoid stagnant pockets.

Clean the platinum ring with a soft cloth and mild detergent, rinse with deionised water, then calibrate with an ORP standard solution (200 mV or 468 mV). Record the deviation value after each calibration — a steadily growing deviation is the earliest sign that the reference cell is ageing.

If communication fails, verify the wiring and then the communication parameters (address, baud rate, parity bit, stop bit). If the value is abnormal, check whether the platinum ring is clean and whether the sensor is damaged, restore the factory calibration value, clean and recalibrate with standard buffer, then check the electrode service life.

Please specify the connection type (bare wire, M12 plug or waterproof aviation plug), cable length (10 m standard) and mounting method so we can confirm the correct accessories. OEM labelling and custom cable lengths are available for volume orders. Send your process conditions — ORP range, temperature, pressure and chemical environment — and our engineers will confirm the configuration.