COS51E Dissolved Oxygen Sensor Product Overview
The COS51E dissolved oxygen sensor is an industrial-grade sensor used for continuous online monitoring of dissolved oxygen concentration in water, widely applied in fields such as wastewater treatment, aquaculture, environmental monitoring, and industrial process control.
The sensor adopts the fluorescence method (LDO) measurement principle, requiring no electrolyte or membrane, with low maintenance and good long-term stability. The following will systematically introduce its technical parameters, installation, commissioning, and maintenance points based on the COS51E Chinese manual.
Download COS51E Chinese Manual.pdf
Measurement Principle and Core Advantages
Fluorescence Measurement Principle
The COS51E sensor operates based on the fluorescence quenching effect. The fluorescent substance on the sensor probe surface emits red light after being excited by blue light. The higher the dissolved oxygen concentration in water, the lower the red light intensity and the shorter its lifetime.
By measuring the fluorescence lifetime, the dissolved oxygen concentration can be converted. The entire process does not consume oxygen, so it is not affected by flow rate or stirring.
Comparison with Traditional Electrochemical Sensors
| Comparison Item | COS51E Fluorescence Method | Traditional Electrochemical Method |
|---|---|---|
| Measurement Principle | Fluorescence Quenching | Galvanic/Polarographic |
| Consumes Oxygen | No | Yes |
| Flow Rate Requirement | None | Requires certain flow rate |
| Maintenance Cycle | Long (6~12 months) | Short (1~2 months) |
| Electrolyte/Membrane | Not required | Requires periodic replacement |
From the table above, the COS51E has significant advantages in maintenance cost and long-term stability, especially suitable for unattended online monitoring scenarios.
Main Technical Parameters
According to the COS51E Chinese manual, its core parameters are shown in the table below for selection and procurement reference.
| Parameter Item | Specification Description |
|---|---|
| Measurement Range | 0~20 mg/L (extendable) |
| Resolution | 0.01 mg/L |
| Measurement Accuracy | ±1% FS or ±0.1 mg/L |
| Response Time | T90 ≤ 60 s |
| Operating Temperature | 0~50 ℃ |
| Protection Rating | IP68 |
| Output Signal | RS485 Modbus / 4-20 mA |
| Supply Voltage | DC 12~24 V |
The above parameters are subject to the actual manual. When purchasing, please verify whether the range, output signal, and installation interface match the on-site requirements.
Installation and Commissioning Steps
Installation Precautions
- The installation location should avoid bubbles, direct strong light, and severe agitation areas.
- The probe must be fully immersed in water; a submersion depth of no less than 10 cm is recommended.
- Avoid installing directly below water inlets or aeration outlets to prevent reading fluctuations.
- The cable should be fixed with a drip loop to prevent moisture from entering the wiring chamber.
Commissioning Steps
- Check whether the wiring is correct and confirm the supply voltage is within DC 12~24 V.
- Power on and preheat for 10~15 minutes until the reading stabilizes.
- Place the probe in oxygen-free water (such as saturated sodium sulfite solution) for zero calibration.
- Place the probe in saturated dissolved oxygen water for full-scale calibration.
- Input the salinity compensation value according to the on-site temperature to complete the setup.
- Record the calibration data and confirm the output signal matches the host computer.
After commissioning, it is recommended to observe continuously for 24 hours to confirm stable readings without jumps before putting into formal operation.
Daily Maintenance and Troubleshooting
Maintenance Points
- Regularly rinse the probe surface with clean water to remove attachments and biofilms.
- Wipe the fluorescent cap with a soft cloth dipped in neutral detergent; do not scrape with hard objects.
- Replace the fluorescent cap promptly when aged or damaged; its typical lifespan is 1~2 years.
- Perform calibration every 3~6 months to ensure measurement accuracy.
Common Faults and Handling
| Fault Phenomenon | Possible Cause | Handling Method |
|---|---|---|
| Reading too high | Fluorescent cap contaminated or aged | Clean or replace the fluorescent cap |
| Reading fluctuates greatly | Bubble interference or unstable flow rate | Adjust installation position |
| No signal output | Power supply or wiring fault | Check power supply and cable |
| Calibration failure | Standard solution expired or contaminated | Replace standard solution and recalibrate |
If the problem persists after handling according to the table above, please refer to the COS51E Chinese manual or contact the manufacturer's technical support.
Selection and Procurement Recommendations
When purchasing the COS51E, it is recommended to focus on the following three points:
- Range matching: Select an appropriate range based on the actual dissolved oxygen range of the water body to avoid wasting accuracy.
- Output interface: Confirm whether the host computer or PLC supports RS485 Modbus or 4-20 mA.
- Installation method: Choose immersion, pipeline, or buoy-type installation accessories based on the tank structure.
For complete technical documentation, click the link at the beginning of the article to download the COS51E Chinese Manual PDF for more detailed wiring diagrams and calibration procedures.