Fluorescent dissolved oxygen sensorThe achievement of precise measurement mainly relies on its special working principle and a series of design features. The following are the key factors for achieving precise measurement:
1、 Working principle
The fluorescent dissolved oxygen sensor operates based on the principle of fluorescence quenching. When light of a specific wavelength (such as blue light) is irradiated onto the fluorescent substance inside the sensor, the fluorescent substance will be excited and emit red light. Due to the quenching effect, oxygen molecules can carry away energy, so the time and intensity of the excited red light are inversely proportional to the concentration of oxygen molecules. The sensor calculates the concentration of oxygen molecules by measuring the phase difference between the excitation red light and the reference light, and comparing it with the internal calibration value.
2、 Design Features
1. High quality fluorescent substances: The sensor uses high-quality fluorescent substances, such as fluorescent coatings containing oxygen sensitive marker molecules, which are sensitive and stable to oxygen molecules, ensuring measurement accuracy.
2. Precise optical system: The sensor is equipped with a precise optical system, including components such as LED light sources and photodiodes, for emitting and receiving fluorescent signals. The high precision and stability of these components help ensure the reliability of measurements.
3. Temperature compensation function: The sensor is equipped with a built-in temperature transmitter and has automatic temperature compensation function. Under different water temperature conditions, sensors can automatically adjust measurement parameters to reduce measurement errors and improve measurement accuracy.
4. Intelligent communication interface: The sensor is equipped with RS485 communication interface and adopts ModBus RTU communication protocol, which can be easily connected to the computer for monitoring and communication. This helps to achieve remote monitoring and management of sensor data, improving the automation and intelligence level of measurement.
3、 Calibration method
To ensureFluorescent dissolved oxygen sensorAccurate measurement and regular calibration are essential. Common calibration methods include zero point calibration, full point calibration, single point calibration, and multi-point calibration.
1. Zero point calibration: Place the sensor in an anaerobic environment, such as boiling and cooling sealed deionized water or using a chemical deoxygenation agent to remove dissolved oxygen from the water. After the sensor reading stabilizes, set its output value to zero.
2. Full point calibration: Place the sensor in saturated air and water for calibration. Usually, pure water is fully aerated at a certain temperature and standard atmospheric pressure to achieve saturation of dissolved oxygen in the water. Immerse the sensor in saturated air-water and adjust the output value of the sensor to the dissolved oxygen concentration value of saturated air-water at that temperature after the reading stabilizes.
3. Single point calibration: Select a standard solution with a known dissolved oxygen concentration (preferably close to the common measurement value of the sensor during actual use), place the sensor in the standard solution, and adjust the output value of the sensor to the dissolved oxygen concentration value of the standard solution after the reading stabilizes. This method is relatively simple to operate, but the calibration accuracy may not be as good as the two-point calibration method.
4. Multi point calibration: Select multiple standard solutions with different dissolved oxygen concentrations (the concentration range should cover the measurement range of the sensor), place the sensor in each standard solution in sequence, and record the output value of the sensor after the reading stabilizes. Then establish a calibration curve through software or manual calculation to improve the accuracy of the sensor throughout the entire measurement range.
The fluorescent dissolved oxygen sensor achieves precise measurement through its unique working principle, high-quality design features, and precise calibration method. These characteristics make fluorescent dissolved oxygen sensors play an important role in environmental protection, aquaculture, biotechnology, and other fields.