Table of Contents Dissolved oxygen (DO) refers to the amount of oxygen dissolved in water. It is expressed as the mass of oxygen per
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Dissolved Oxygen Meter
Our RS-LDO*-N01-2-20-EX dissolved oxygen meter is a device for measuring the concentration of dissolved oxygen in water. It adopts the principle of fluorescence measurement, does not consume oxygen, and does not require electrolytes. The dissolved oxygen measurement range is 0~20mg/L. Built-in temperature transmitter with automatic temperature compensation function.
- Model: RS-LDO*-N01-2-20-EX
- MOQ: 1 PCS
- Delivery date: within 24 hours
- Price: $84
About - Dissolved Oxygen Meter
Our dissolved oxygen sensors are divided into two types: seawater and freshwater. The calibration function provides a simpler and more convenient way to calibrate. Water dissolved oxygen meter can be widely used in water treatment, aquaculture, rivers, lakes, and seawater quality monitoring industries.
Features
- Dissolved oxygen measurement range is 0~20mg/L (0~200% saturation).
- The Modbus communication address can be set, and the baud rate can be modified.
- The dissolved oxygen sensor uses a wide voltage power supply, DC 10~30V can be.
- Uses imported high-quality fluorescent membrane.
- The principle of fluorescence measurement is adopted, no oxygen is consumed, and no electrolyte is required.
- Free cloud platform for the data view.
Parameters
| Power supply | DC 10~30V |
|---|---|
| Signal output | RS485 |
| Power consumption | 0.2W |
| Working principle | Fluorescence Method |
| Measure range | 0~20mg/L (0~200% saturation) |
| Measure error | ±3%FS; ±0.5℃ (25℃) |
| Resolution | 0.01mg/L; 0.1%; 0.1℃ |
| Response time | ≤60s |
| Operating conditions | 0~40℃ |
| Fluorescent film lifespan | 1 year under normal use |
| Protect class | IP68 |
| Pressure resistance | 0.6MPa |
| Electrode wire length | Default 5m |
| Shell material | Standard type: Corrosion-resistant plastic, stainless steel; Economy type: Corrosion-resistant plastic |
Working principle
Fluorescence Dissolved Oxygen: Based on the quenching principle of active fluorescence by specific substances in physics.
By measuring the phase difference between the excited red light and the reference light, and comparing it with the internal calibration value, the concentration of oxygen molecules can be calculated.
Compared to polarography, fluorescence measurement does not require the consumption of oxygen in water, and it has a faster response time, stronger anti-interference ability, and more accurate measurement results.
Calibration
1. Zero oxygen standard solution preparation
In a place without wind and direct sunlight, take purified water (distilled water or deionized water) deep enough to cover the stainless steel part of the electrode. For every 95 g of water, add 5 g of anhydrous sodium sulfite. Stir thoroughly until fully dissolved to obtain a 5% sodium sulfite solution. Let it stand for 1 hour to ensure that the oxygen in the solution is completely consumed. If conditions allow, a trace amount of cobalt chloride can be added as a catalyst.
2. 100% oxygen environment preparation
In a place without wind and direct sunlight, take purified water (distilled water or deionized water) deep enough to cover the stainless steel part of the electrode. Use an air pump to continuously aerate the water for 1 hour, then let it stand for 30 minutes to obtain air saturated water.
Alternatively, use a sealed container, take a small amount of water, and shake it vigorously for 30 seconds to obtain air saturated with water vapor. During calibration, keep the fluorescent membrane about 1 cm above the water surface, ensuring the membrane is moist but without water droplets.
3. In the configuration tool, find the Dissolved Oxygen option under the Water Quality Sensor tab.
4. Place the dissolved oxygen sensor in the 100% oxygen environment. After the dissolved oxygen reading stabilizes, click the Full Scale Calibration button to complete the 100% oxygen saturation calibration.
5. Then place the sensor into the zero oxygen standard solution. Gently stir to speed up the response, then let it stand. After the dissolved oxygen reading stabilizes, click the Zero Calibration button to complete the zero oxygen calibration.
Note:
In each calibration environment, the device should be left stationary for a sufficient amount of time to ensure that the device temperature is the same as the ambient temperature.
FAQs - Dissolved Oxygen Meter
Why does a negative value appear when measuring 0% oxygen? Is this normal?
A negative value is normal. During calibration, the value recorded corresponds to the fluorescence lifetime at 0 percent oxygen. In actual measurement, this value can fluctuate, and long term use may also introduce drift.
In practice, it is possible to apply a limit and force all values below zero to be displayed as zero. However, if this is done, users with their own calibration requirements would not be able to judge whether the 0 percent oxygen value is truly stable during calibration.
What should be noted when using a dissolved oxygen meter?
Avoid using it in organic solvents, and do not clean the membrane cap with organic solvents. The fluorescent membrane uses an embedding method to fix the fluorescent material within the film. Organic solvents can cause the fluorescent material to leach out.
What is the role of salinity and atmospheric pressure?
Our product actually measures dissolved oxygen saturation in percent. The dissolved oxygen concentration is calculated from this value using salinity, atmospheric pressure, temperature, and other constants. Changes in salinity and atmospheric pressure affect the dissolved oxygen concentration at the same saturation level. The general trends are: higher salinity results in lower dissolved oxygen concentration, and higher atmospheric pressure results in higher dissolved oxygen concentration.
How to install a dissolved oxygen meter?
The sensor should be fixed and installed below the liquid surface. During installation and use, avoid impact or scratching of the fluorescence membrane head, and prevent the membrane head from being covered by bottom sediments. Remove the rubber protective cap before use. The dissolved oxygen electrode is equipped with an NPT 3/4 thread and can be used with our waterproof pipe. Feed the cable through the pipe, then screw the sensor into the threaded port of the waterproof pipe.
How to maintain a dissolved oxygen meter?
For the outer surface of the electrode: Rinse with tap water and gently wipe with a soft, damp cloth. For stubborn contamination, a small amount of household detergent may be added to tap water for cleaning.
For the outer surface of the optical (fluorescent) cap: Rinse the sensor’s optical window with clean water to remove surface contaminants. If wiping is necessary, use a soft cloth and wipe gently. Do not scrape or apply excessive force, as this may damage the fluorescent membrane and result in inaccurate measurements.
If dust or moisture has entered inside the optical (fluorescent) cap. Unscrew the optical cap and rinse the inner surface of the cap and the instrument’s optical glass window with tap water. If oily contaminants are present, clean with tap water mixed with a small amount of household detergent. After cleaning, thoroughly rinse off any detergent residue, then dry all cleaned surfaces with a lint-free soft cloth. Finally, place the components in a dry environment and allow any remaining moisture to fully evaporate.
What is the dissolved oxygen concentration when measuring in air, and how does it change with temperature?
Under normal conditions, humid air is considered to represent 100% dissolved oxygen saturation. The dissolved oxygen concentration varies with temperature: as temperature increases, the dissolved oxygen concentration at saturation decreases. This is because higher temperatures intensify molecular motion, making oxygen molecules more likely to escape from the water.
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