Many projects start with one question: “What is the pH range?” It is an important question, but it is not enough to choose an industrial pH meter.
The complete measuring loop includes the controller, electrode, temperature compensation, installation point, signal output and maintenance routine. A controller can have a wide range and still be a poor fit for a liquid that coats the glass, attacks the reference junction or cannot be reached safely for cleaning.
Here is the practical approach: select the controller and electrode as one loop, then confirm how the measurement will connect to the control system.
The short version
- Define the liquid and operating conditions before comparing models.
- Select the electrode for the chemistry, not only for the pH range.
- Confirm the exact 4–20mA, RS485 and relay functions on the chosen model.
- Plan installation, calibration and cleaning before automatic control is enabled.
1. Start with the process, not the product name
Before comparing an industrial pH meter, write down the conditions at the measuring point:
- Is the required measurement pH, ORP or both?
- What are the normal and maximum measurement ranges?
- What are the normal and maximum temperature and pressure?
- Does the liquid contain fluoride, salts, oils, suspended solids, heavy metals or organic deposits?
- Will the electrode be installed in a tank, pipe, bypass flow cell or immersion assembly?
- What cable length and maintenance access are required?
- Does the control system need 4–20mA, RS485 Modbus RTU, relay contacts or more than one of these?
This information changes the selection. A wastewater neutralization tank, an acid-mist scrubber and a clean process-water line may all measure pH, but they do not necessarily need the same electrode or installation.
2. Choose the electrode for the liquid
The electrode is the part that contacts the process. It should not be treated as an accessory chosen after the controller.
For general industrial pH monitoring, TB84H0 can be considered after the liquid, temperature, pressure, installation thread and cable are confirmed. A standard pH sensor may not be suitable when the process contains fluoride, heavy deposits, high salt or aggressive chemicals.
TB84H7W is intended for selected fluoride-containing applications where an HF-resistant pH sensor may be required. HF resistance does not establish complete chemical compatibility. The full chemistry and fluoride concentration still need to be reviewed.
For oxidation-reduction measurement, TB84R1 can be considered when ORP is an appropriate process indicator. ORP shows the combined oxidation-reduction condition at the electrode surface. It is not a direct concentration measurement for a specific chemical.
3. Compare the controller by the way it will be used
The following table is a practical starting point for three Tenber pH/ORP controllers. It is based on the current model manuals and does not replace an application review.
| Model | Measurement and range | Documented integration | Typical selection direction |
|---|---|---|---|
| PH-301 | pH 0–14; ORP −1999 to +1999 mV; temperature 0–100°C | Two isolated 4–20mA outputs and two HI/LO control points | For compatible analogue inputs and separate measurement and temperature signals. |
| PH-302 | pH −2 to +16; ORP −2000 to +2000 mV; temperature −10 to +130°C | One isolated 4–20mA output, RS485 Modbus RTU and two relay controls | For compact panels that need digital communication as well as analogue and relay functions. |
| PHS-3301 | pH −2 to +16; ORP −2000 to +2000 mV; temperature −10 to +150°C | Two isolated 4–20mA outputs, RS485 Modbus RTU, three relay functions and data logging | For a 144 mm controller that needs broader integration and documented record storage. |
The interface is model-specific. The verified PH-301 manual lists isolated 4–20mA outputs and relay control, while PH-302 and PHS-3301 documentation identifies RS485 Modbus RTU. Confirm the exact model, output mapping, isolation, load and communication settings before wiring.
A quick way to narrow the choice
- Choose PH-301 when the project needs a 144 mm controller with separate analogue signals for pH/ORP and temperature, plus two HI/LO control points.
- Choose PH-302 when panel space is tighter and the project needs one isolated 4–20mA output, RS485 Modbus RTU and two relays.
- Choose PHS-3301 when a 144 mm controller needs two isolated current outputs, RS485, three relay functions and recorded data.
Panel fit can also decide the model. The documented PH-301 panel opening is 138 × 138mm, PH-302 uses a 92.5 × 92.5mm opening, and PHS-3301 uses a 141 × 141mm opening. Confirm the current drawing before cutting a panel.
4. Decide what the signal needs to do
4–20mA is commonly used to transmit a measured value to a compatible PLC, recorder or DCS. Check the number of channels and what each channel represents. PH-301 documents one output for pH/ORP and another for temperature. PH-302 documents one isolated pH/ORP current output. PHS-3301 documents two isolated current outputs, with pH/ORP and temperature mappings available through its output settings.
RS485 Modbus RTU can carry digital measurement values and settings, but the controller and receiving system must use matching communication parameters. Check the address, baud rate, register map, wiring and signal reference before commissioning.
Relay outputs can support compatible alarms or dosing-control arrangements. They do not replace the complete safety design. Review mixing time, dosing-pump capacity, alarm limits, interlocks and sensor-failure behavior before automatic chemical addition is enabled.
5. Plan the installation and temperature compensation
Install the electrode where the liquid is representative and the sensing area stays wetted. Avoid trapped air, dead zones and direct chemical-feed points. The electrode also needs enough clearance for calibration, cleaning and replacement.
Temperature compensation may be automatic or manual, depending on the controller and process arrangement. PH-301 documents NTC30K, PT1000 and manual compensation. PH-302 documents Pt1000, NTC10K and manual mode. PHS-3301 documents Pt1000, NTC10K and manual compensation across a wider temperature range.
When automatic compensation is selected, the connected probe type must match the controller setting. A wrong probe selection can make both the temperature value and compensated pH reading unreliable.
6. Calibrate before connecting automatic control
Finish the wiring and check the receiving device before applying power. Then follow the current controller manual for initial settings and calibration.
For pH measurement, use suitable standard solutions and complete the calibration points required for the process range. For ORP, use a suitable reference solution and check the result against the intended process application. Before enabling dosing or alarms, compare the displayed value with an accepted reference method and verify the signal direction.
Cleaning and calibration intervals should follow the fouling and drift observed at the site. The PHS-3301 manual identifies electrode efficiency below 80% as an indication that the electrode may be ageing. That is a maintenance check for the documented controller procedure, not a universal service-life guarantee for every electrode.
Common mistakes to avoid
Choosing by pH range alone
A wide controller range does not make every electrode suitable for strong acid, fluoride, oil, suspended solids or high-temperature service.
Assuming every model has Modbus
Communication functions vary by model. Confirm RS485, baud rate, address and register information on the exact controller before promising integration to a customer.
Connecting a relay to an unsuitable load
Relay ratings and contact protection must match the connected device. Inductive and capacitive loads may need an external protection circuit.
Enabling dosing before checking the complete loop
Verify the electrode, calibration, output scaling, relay direction, alarm behavior and mixing delay before automatic chemical addition.
What to send for model selection
For a practical quotation, send the measurement parameter, liquid composition, expected range, temperature, pressure, installation method, cable length, required output, communication, relay or dosing logic, quantity and destination country.
If the liquid contains fluoride, strong acid, strong alkali, heavy metals, oil, high salt or organic deposits, include that information in the first message. It may affect the electrode, holder, cleaning method and maintenance plan.
This is the information Tenber needs to review the controller, electrode, temperature probe and installation as one measuring configuration. It is more useful than choosing from the parameter name alone.
Need help matching the controller and electrode?
Send the process conditions first so Tenber can review the complete measuring configuration. Discuss Your Application