DODO AQUA pH
Industrial Online pH Sensor
pH · Temperature
- 0-14 pH, ±0.1 pH
- RS-485 Modbus-RTU
- IP68, 3/4" NPT immersion
- DC 12-24 V, < 0.3 W
- Automatic temperature compensation
- 5 m cable, GX12 fitted
Works with DODO LOGGER, the DODOTiK Platform and the DODOLINK app — see how.
Overview
DODO AQUA pH (DOT-PHS-200) is a submersible industrial pH sensor with the signal conditioning built into the probe body, so what leaves the sensor is already a calibrated digital pH value on RS-485 Modbus-RTU - no separate transmitter, no analog pH loop, no high-impedance cable run to protect.
That matters more for pH than for any other measurand. A raw glass electrode puts out a few tens of millivolts across hundreds of megohms, and the usual field failure is not the electrode but the cable between the electrode and a transmitter mounted somewhere drier. Digitising at the probe removes that cable from the measurement entirely.
The sensing element is a dual high-impedance differential amplifier feeding a patented reference system: the internal reference solution bleeds outward through a microporous salt bridge under at least 100 kPa (1 bar), so the junction is always flowing out rather than drawing process liquid in. The factory rates that forward bleed at over 20 months, roughly twice the service life of a conventional industrial reference.
Key features
- Full range - 0-14 pH at 0.01 pH resolution, ±0.1 pH accuracy
- Compensated - automatic temperature compensation via a built-in NTC element
- Digital at the probe - RS-485 Modbus-RTU out; no pH transmitter needed
- Long-life reference - pressurised microporous salt bridge, 20+ months of forward bleed
- Submersible - IP68, 3/4" NPT thread for tank, pipe or submerged mounting
- Two-point calibration - over the bus, with the standard 6.86 / 4.00 / 9.18 buffers
- Plug-in - 5 m cable with the DODO LOGGER GX12 connector fitted as standard
Measured parameters
| Parameter | Unit | Range | Accuracy | Resolution |
|---|---|---|---|---|
| pH | pH | 0-14 pH | ±0.1 pH | 0.01 pH |
| Temperature | °C | 0-65 °C (working range) | — (compensation element, not a specified output) | 0.1 °C |
Technical specifications
Measurement
| Parameter | Value |
|---|---|
| Measured parameters | pH, with temperature as a compensation channel |
| Measuring range | 0-14 pH |
| Resolution | 0.01 pH |
| Accuracy | ±0.1 pH |
| Temperature compensation | Automatic (NTC) |
| Calibration | Two-point - zero at pH 6.86, slope at pH 4.00 or 9.18 |
Electrical
| Parameter | Value |
|---|---|
| Supply voltage | DC 12-24 V ±10 % |
| Power consumption | < 0.3 W @ 12 V |
| Output | RS-485, Modbus-RTU |
| Baud rate | 9600 (default) |
| Frame format | 8 data bits, 1 stop bit, no parity (8N1) |
| Default slave address | 6 |
| Addressing | Field-changeable over the bus, range 1-127 |
| Cable | 5 m, Φ6 mm shielded, corrosion-resistant jacket, GX12 4-pin female fitted; other lengths on request |
Mechanical & environmental
| Parameter | Value |
|---|---|
| Body diameter | Φ30 mm |
| Overall length | 185 mm |
| Wetted material | POM |
| Mounting | Immersion, 3/4" NPT thread - tank, pipe or submerged |
| Working temperature | 0 … +65 °C |
| Working pressure | < 0.2 MPa |
| Ingress protection | IP68 |
Plug DA-PH into DODO LOGGER and it is already on your phone
No firmware reflash, no driver to write, no backend deployment. The logger self-describes its schema to the platform, so a new sensor appears in the dashboard and in the app on its own.
1 · Plug in
The fitted GX12 4-pin connector screws onto the logger's Modbus RS-485 socket. No stripping, no terminal block, no tools. Up to four sensors per logger.
2 · Select it
DA-PH is in the logger's no-code sensor library. Pick it in the web interface, assign a slot, and it starts logging.
3 · Logged locally
Every reading to microSD, always on, offline included. CSV download straight off the card.
4 · Live in the cloud
MQTT/TLS to the DODOTiK Platform — live dashboards, full history, alert thresholds, device management.
5 · On a phone
The same readings and alerts in DODOLINK for iOS and Android, for whoever is out in the field rather than at a desk.
Nothing here is lock-in. DA-PH is a standard Modbus-RTU device on a standard RS-485 bus. The DODO LOGGER, the platform and the app are the fastest route from probe to dashboard, not the only one — the full register map is published below and in the datasheet, and the sensor can be ordered with bare leads for a PLC, DCS, SCADA or paperless recorder.
Dimensions
| Dimension | Value |
|---|---|
| Overall length | 185 mm |
| Body diameter | Φ30 mm |
| Electrode guard diameter | Φ22 mm |
| Process thread | 3/4" NPT, both ends |
| Wrench flat | 28 mm |
| Cable length | 5 m (standard) |
Wiring — GX12 4-pin connector
The cable is terminated in a GX12 4-pin female aviation connector, fitted as standard. It screws directly onto the DODO LOGGER Modbus RS-485 socket. For a third-party logger or a terminal block, order the bare-lead variant rather than cutting the connector off at the sensor's gland — the gland is part of the IP68 seal.
| Pin | Signal | Function |
|---|---|---|
| 1 | VCC | Power + (DC 12-24 V) |
| 2 | GND | Ground |
| 3 | A (D+) | RS-485 A |
| 4 | B (D−) | RS-485 B |
Modbus RTU register map
RS-485 Modbus-RTU, 9600 baud, 8 data bits, 1 stop bit, no parity. Default slave address 6. Published in full so the sensor can be read by any Modbus master — PLC, DCS, SCADA or a paperless recorder.
| Register | Value | Access | Notes |
|---|---|---|---|
| 0x0000 | Measured value + temperature | Read | 4 registers: pH value, pH decimals, temperature value, temperature decimals |
| 0x1000 | Zero calibration | Write | In pH 6.86 buffer; write 0 |
| 0x1002 | Slope calibration (pH 4.00) | Write | In pH 4.00 buffer; write 0 |
| 0x1004 | Slope calibration (pH 9.18) | Write | In pH 9.18 buffer; write 0 |
| 0x1006 | Zero calibration value | Read | Returns the stored zero offset |
| 0x1008 | Slope calibration value | Read | Slope × 1000 |
| 0x1010 | Temperature calibration | Read / Write | Write actual temperature × 10; read the stored offset × 10 |
| 0x2002 | Device address | Read / Write | Default 6, range 1-127 |
| 0x2020 | Factory reset | Write | Write 0 - restores factory calibration |
Calibration
Calibration is performed over the bus — there is no handheld meter to carry and no transmitter to adjust.
The sensor is calibrated at the factory. Do not recalibrate a probe that is reading correctly - each calibration writes over the stored reference and a calibration performed in a badly made buffer is worse than none.
Zero (pH 6.86). Make up 250 mL of pH 6.86 buffer from distilled water and one sachet of calibration powder, stirring until fully dissolved. Stand the probe in it for 3-5 minutes. If the reading has settled anywhere other than 6.86, write the zero-calibration command.
Slope (pH 4.00 or 9.18). Repeat with the buffer that brackets your process: 4.00 for acidic media, 9.18 for alkaline. Rinse the probe between buffers - carry-over from one buffer into the next is the main cause of a bad slope.
Buffer values move with temperature. The factory reference table gives pH 6.86 as 6.98 at 0 °C and 6.83 at 50 °C; calibrate near process temperature where you can.
Calibration commands
| Operation | Request | Response |
|---|---|---|
| Zero, in pH 6.86 buffer | 06 06 10 00 00 00 8C BD | 06 06 10 00 00 00 8C BD |
| Slope, in pH 4.00 buffer | 06 06 10 02 00 00 2D 7D | 06 06 10 02 00 00 2D 7D |
| Slope, in pH 9.18 buffer | 06 06 10 04 00 00 CD 7C | 06 06 10 04 00 00 CD 7C |
Applications
Drinking-water treatment - coagulation, softening and final-stage pH control
Wastewater and effluent - neutralisation before discharge, consent monitoring
Aquaculture - pond and recirculating-system water quality
Hydroponics and fertigation - nutrient-solution pH control
Chemical dosing - acid/alkali balance in a process loop
Industrial process water - boiler feed, cooling circuits, scrubber liquor
Before you specify it
Limits worth knowing before the order goes in, rather than after the sensor is in the ground.
- Mounting below 15° above horizontal traps a bubble on the reference junction.
Ordering information
| Order code | Description |
|---|---|
| DA-PH | DODO AQUA pH (DOT-PHS-200), 0-14 pH, RS-485 Modbus-RTU, 5 m cable with GX12 4-pin female connector |
| DA-PH-L10 | As DA-PH, 10 m cable |
| DA-PH-L20 | As DA-PH, 20 m cable |
| DA-PH-BL | As DA-PH, bare leads instead of the GX12 connector (for PLC, DCS or terminal-block wiring) |
What's in the box
- DODO AQUA pH sensor with 5 m cable, GX12 4-pin female connector fitted
- Calibration powder, 3 sachets (pH 6.86, 4.00, 9.18)
- Test certificate
Quality and warranty
- IP68 sealed body, POM wetted parts
- 72-hour burn-in and stability test on every unit before shipment
- Warranty: 1 year from date of sale, excluding damage from improper use
- The glass electrode is a wearing part; reference life is rated at 20+ months of continuous service
Handling and maintenance
- Rinse the glass in distilled or deionised water before each measurement and blot it dry with filter paper - carrying droplets of the previous sample into the next one is the most common source of pH error.
- Store the probe wet. When it is out of service, cap it with the protective sleeve filled with 3.5 mol/L potassium chloride, or stand it in a vessel of the same solution. A glass electrode allowed to dry out is often not recoverable.
- Never store it in distilled water or in a protein solution, and keep silicone grease away from the glass.
- If the glass goes translucent or scales up, wash it in dilute hydrochloric acid and rinse with water.
- Keep the terminal dry. If it is contaminated, wipe with absolute alcohol and dry before reconnecting.
- If the probe will no longer hold a calibration after cleaning, the electrode has reached end of life. Replace it.
Frequently asked questions
Does DODO AQUA pH work with a PLC, SCADA or a third-party data logger?
Yes. DA-PH is a standard RS-485 Modbus-RTU device at 9600 baud, 8N1, so any Modbus master can read it - PLC, DCS, SCADA or a paperless recorder. The full register map is published in the datasheet, and the sensor can be ordered with bare leads instead of the GX12 connector for terminal-block wiring. There is no proprietary driver and no lock-in.
What is the default Modbus address of DA-PH?
6. The address is changeable in the field over the bus, so several sensors can share one RS-485 pair as long as each has a unique address.
How do I connect DODO AQUA pH to DODO LOGGER?
Screw the fitted GX12 4-pin connector onto the logger's Modbus RS-485 socket - no stripping, no terminal block, no tools. DA-PH is in the logger's no-code sensor library, so an installer selects it in the web interface and it begins logging to microSD and publishing to the DODOTiK Platform and the DODOLINK app. No firmware reflash, no backend change.
What does DA-PH measure, and how accurately?
pH: 0-14 pH, accuracy ±0.1 pH.
How do I order DA-PH, and what does it cost?
DA-PH is sold direct and through distributors. Pricing depends on configuration and quantity, so request a quote with the order code and the quantity you need and DODOTiK will come back with export pricing and volume tiers. Available configurations: DA-PH; DA-PH-L10; DA-PH-L20; DA-PH-BL.
Is there anything to watch out for when specifying DA-PH?
Mounting below 15° above horizontal traps a bubble on the reference junction.
More from DODO AQUA
Request a quote for DA-PH
Sold direct and through distributors. Tell us the order code, the quantity and the destination country and we will come back with export pricing, volume tiers and lead time.