Dissolved Oxygen Probe AT-SB-PROBE-DO-T-C1
Datasheet
1. Introduction
"The SENSBLUE RS-485 Dissolved Oxygen Probe (AT-SB-PROBE-DO-T-C1) is designed for the aquaculture industry. It offers stable online monitoring, providing excellent performance compared with traditional sensors. As a fluorescence-based dissolved oxygen sensor, it requires no membrane or electrolyte and features strong anti-interference capabilities. It does not require frequent calibration, has no oxygen consumption, and no flow rate limitations. Additionally, it includes automatic temperature and gas pressure compensation, a fast reaction speed, and a long service life. This makes it an economical and convenient choice for the real-time dynamic monitoring of oxygen levels in aquaculture."
2. Features
- Digital sensor, RS485 output, support MODBUS
- No electrolyte required, strong anti-interference, no need for frequent calibration; no oxygen consumption, no flow rate limit;
- Built-in temperature sensor, automatic temperature compensation;
- Tailor-made for the breeding market, with cost-effective performance
3. Technical Specifications
| Measurement principle | Fluorescence method |
| Range | 0-20mg/L or 0-200% saturation |
| Accuracy | ±3% |
| Casing material | 316L(KWS-630) Titanium alloy(KWS-630T) |
| Max water depth | 30m |
| Response time | 60s |
| Temperature range | 0-50℃ |
| Sensor interface | RS-485, MODBUS protocol |
| Power consumption | -0.1W (recommended power supply: DC9-24V, current>50mA) |
| Assembly | M22*1.5 (optional accessories can be converted to
NPT3/4 thread), immersion installationa |
| Sensor dimensions | Φ22mm*152.7mm |
| Probe cable length | 10 meters (default), customizable |
| Calibration | One or two-point calibration |
| Fluorescent cap life | Guaranteed to use for one year (under normal use) |
4. Dimensions and Wiring
5. Installation and Pinouts
5.1 Installation
(1) Removing the protective cover Prior to installation, please remove the rubber protective cap from the front of the dissolved oxygen sensor and keep it in a safe place.
(2) Wiring and power supply:
1. The sensor's watertight connector, and the cable (or female connector) must be tightly screwed together to prevent water ingress.
2. Do not use the sensor cable to suspend the sensor. It is recommended to install a cable protective sleeve to ensure the connection remains powered and watertight.
3. Before switching on the power, ensure that the supply voltage and wiring sequence are correct.
(3) Sensor installation
1. The unit features an M22*1.5 rear thread (optional accessories are available to convert this to an NPT 3/4" thread) for fixed or shell-clamp installation. (Note: It is recommended to install the sensor with the electrode facing downwards).
2. To account for fluctuating water levels, it is recommended to install the sensor at least 30cm below the lowest water line to avoid prolonged exposure to air during measurement.
3. The sensor must be securely fixed to prevent probe damage caused by water flow or other external factors.
5.2 Pinouts
| Pinouts | |
|---|---|
| 1 - Pin 12-24V DC | 4 - RS485 B- |
| 2 - GND | 5 – NA |
| 3 - RS485 A+ | 6 - NA |
| 7 - NA | |
6. Calibration
6.1 Calibration method
The dissolved oxygen sensor supports single-point (typically the 100% saturation point) or two-point calibration. The calibration parameter uses a percentage scale (expressed as a decimal, e.g. 0.96 for 96%). Single-point calibration primarily adjusts the K-value (slope), whereas two-point calibration adjusts both the K and B values (slope and offset).
6.2 Standard solution preparation
1.) Zero-point standard solution To prepare the zero-point standard solution, pour 200ml of distilled water into a beaker. Gradually add anhydrous sodium sulfite while stirring until the solution is saturated (i.e., when it can no longer dissolve and solid crystals begin to appear). The resulting mixture is your zero-point standard solution.
2.) 100% oxygen environment Pour 200ml of pure or distilled water into a beaker. Use a small aerator to oxygenate the water thoroughly for 10–15 minutes (larger volumes of water will require more time).Note: If on-site conditions are restricted, the sensor can be cleaned and a saturation-point calibration can be performed in open air, though accuracy may be slightly reduced.
6.3 Manual calibration calculation of K and B example (taking 2-point calibration as an example)
First, restore the user calibration data to the default settings: K=1, B=0 (refer to the Modbus documentation for details). Clean the sensor and place it in a 100% oxygen environment (air). Read the dissolved oxygen value and wait for the data to stabilize. The value should be close to 1 (i.e. 100% saturation), for example, 0.96; record this value as Y. Wash the sensor again and place it in the zero-point standard solution, ensuring the front end of the sensor is completely immersed. Read the dissolved oxygen value and wait for the data to stabilize at a value close to 0, for example, 0.015; record this as X. Calculate the new K and B values using the following formulas:
K = 1 - 0 / Y – X B = - K x X
Finally, write the calculated K and B values into the sensor registers (see the Modbus documentation for further details).
6.4 Required equipment and materials
Anhydrous sodium sulfite powder; Deionized water or distilled water (such as Watsons distilled water); Beaker, gloves, stirring rod, small aerator.
7. Maintenance schedule and methods
7.1 Maintenance cycle
Different from the electrochemical principle of dissolved oxygen probes, fluorescence dissolved oxygen probes do not consume oxygen, have no filling fluid, etc., and do not require frequent maintenance. Normal cleaning and user calibration are sufficient.
| Maintenance tasks | Maintenance cycle (cleaning, calibration) |
|---|---|
| Cleaning the sensor | Recommended every 2~3 weeks (extended for automatic cleaning brushes. Shortened for those without cleaning brushes and large biomass) |
| Inspecting the sensor and fluorescent cap for damage | Check every 30 days |
| Replacing the fluorescent cap | Replace once a year |
| Calibrating the sensor | Recommended every 30 days for frequent use; before each use for occasional use; or adjust according to actual working conditions on site. |
Note: The maintenance frequency in the above table is only a suggestion. Please ask maintenance personnel to maintain the sensor according to the actual use of the sensor; however, it is recommended to replace the fluorescent cap once a year.
7.2 Maintenance methods
(1) Sensor maintenance
a.) Cleaning the outer surface of the sensor: Use tap water to clean the outer surface of the sensor. If there are still debris left, wipe it with a damp soft cloth. For some stubborn dirt, you can add some household detergent to the tap water to clean it;
b.) Cleaning the outer surface of the fluorescent cap: Remove the protective cover at the front of the sensor (if any), rinse the dirt on the sensor light window with clean water, and finally put the protective cover on; if you need to wipe it, please wipe it gently with a soft cloth and do not scratch it hard, otherwise, it will scratch or break the fluorescent film layer, and the sensor will not work properly.
c.) Cleaning the inner surface of the fluorescent cap: If water vapor or dust invades the inside of the fluorescent cap, the cleaning steps are as follows:
- Remove the fluorescent cap and rinse the inner surface of the fluorescent cap with tap water;
- For dirt containing fat and oil, use warm water with household detergent to clean it;
- Rinse the inner surface of the fluorescent cap with deionized water;
Gently wipe all surfaces with a clean lint-free cloth and place it in a dry place to allow the water to evaporate completely.
d.) Check the sensor body and cable: The cable should not be tight during normal operation, otherwise there is a risk of cable breakage, resulting in communication abnormalities; check whether the sensor housing is damaged due to corrosion or other reasons.
e.) Daily storage of the fluorescent cap: When not in use, place it in a protective cover with a moist sponge and check and rehydrate it regularly to keep the fluorescent film moist for a long time. If the head of the sensor fluorescent cap is dry for a long time, the measurement results will drift. It needs to be soaked in water for 48 hours before continuing to work.
(2) Precautions
Avoid the inner surface of the fluorescent cap from being exposed to sunlight. Please do not scratch the fluorescent film with your hands. Avoid applying any mechanical stress (pressure, scratches, etc.) directly to the fluorescent film during use.
8. FAQ
The following table lists possible problems with dissolved oxygen sensors and their solutions. If your problem is not listed or the solution does not solve your problem, please contact us.
| Fault phenomenon | Possible causes | Solution |
|---|---|---|
| The probe cannot communicate or does not display the measurement result | Error in connection between controller
and cable |
Reconnect the controller
and cable |
| Cable failure | Contact us | |
| The measurement value is too high, too low or the value is continuously Unstable | Foreign objects attached to the outer surface of the fluorescent cap | Clean the outer surface of the fluorescent cap |
| The fluorescent cap is damaged | Replace the fluorescent cap | |
| The fluorescent cap has exceeded its service life | Contact us | |
| Internal hardware failure of the probe | ||
| The temperature measurement value exceeds the measurable range or the reading is garbled | Temperature sensor or probe failure | Contact us |
9. Modbus Protocol
The RS485 communication protocol uses MODBUS communication protocol, and the sensors are used as slaves.
| Baud rate | 9600 |
| Starting position | 1 |
| Data bits | 8 |
| Stop bit | 1 |
| Check digit | N |
Read and write data (standard MODBUS protocol).
The default address is 0x01, the address can be modified by register
Reading data
Host call (hexadecimal)
01 03 00 00 00 01 84 0A
| Code | Function Definition | Remarks |
| 01 | Device Address | |
| 03 | Function Code | |
| 00 00 | Start Address | See register table for details |
| 00 01 | Number of registers | Length of registers (2 bytes for 1 register) |
| 84 0A | CRC checksum, front low and back high |
Slave answer (hexadecimal)
01 03 02 00 xx xx xx xx
style="width: 20%;" !Code style="width: 40%;" !Function Definition style="width: 40%;" !Remarks| 01 | Device Address | |
| 03 | Function Code | |
| 02 | Number of bytes read | |
| XX XX | Data (front low and back high DCBA) | See register table for details |
| XX XX | CRC checksum, front low and back high |
Writing data
Host call (hexadecimal)
01 10 1B 00 00 01 02 01 00 0C C1
| Code | Function Definition | Remarks |
| 01 | Device Address | |
| 10 | Function Code | |
| 1B 00 | Register Address | See register table for details |
| 00 01 | Number of registers | Number of read registers |
| 02 | Number of bytes | Number of read registers x2 |
| 01 00 | Data (front low and back high DCBA) | |
| 0C C1 | CRC checksum, front low and back high |
Slave answer (hexadecimal)
01 10 1B 00 00 01 07 2D
| Code | Function Definition | Remarks |
| 01 | Device Address | |
| 10 | Function Code | |
| 1B 00 | Register Address | See register table for details |
| 00 01 | Returns the number of registers written | |
| 7D 2D | CRC checksum (front low and back high) |
Register Table
| Start address | Command Description | Number of registers | Data format (hexadecimal) |
| 0x1100H | User calibration K/B (read/write)
Note: K and B need to be read and written at the same time, and separate reading and writing are not supported. |
4 | 8 bytes in total 00~03: K 04~07: B
To read K for example, read out as 4 bytes of data (low bit in front, DCBA format, need to convert this data to floating point) To write k, for example, we need to convert k to 32-bit floating point and write it in (DCBA format) |
| 0x2700H | Fluorescent cap parameters settings | 16 | 32 bytes in total
00~03：L0 04~07：L1 08~11：L2 12~15：L3 16~19：TanZero 20~23：T0 24~27：T1 28~31： T2 DCBA format, this data needs to be converted to floating point numbers |
| 0x2600H | Dissolved oxygen value acquisition | 6 | 12 bytes in total
00~03: Temperature values 04~07: Dissolved oxygen percentage 08~011: Dissolved oxygen mg/L Reads the temperature value / dissolved oxygen value as 4 bytes of data each (low bit first, DCBA format, this data needs to be converted to floating point number) |
| 0x3000H | Device address
(read / write) |
2 | 00~01: Device address Settable in the range 1 to 254 e.g. get data as 02 00 (low bit first means address is 2) To write to address 15, for example, write 0F 00 (lower bit first) to the corresponding address When the current device address is unknown, FF can be used as a generic device address to interrogate the current device address |
| 0x1500H | Setting salinity values
(read / write) |
2 | 4 bytes in total 00~03: Salinity value Default is 0, unit ppt, DCBA format, this data needs to be converted to floating point number) |
| 0x2400H | Set air pressure value
(read / write) |
2 | 4 bytes in total 00~03: Air pressure value The default standard atmospheric pressure is 101.325, unit kpa, DCBA format, this data needs to be converted into a floating-point number |