RS485 Interface Dissolved Oxygen Sensor Anti Interference KFDO601

KFDO601 Online Fluorescence Dissolved Oxygen No Electrolyte Is Required And Will Not Be Polarized No Oxygen Consumption

 

 

1.Difference between polarographic and fluorescence measurements of dissolved oxygen

 

 

1: Fluorescence method dissolved oxygen measuring instrument is based on the principle of fluorescence quenching. The fluorescent material at the front of the sensor is a special platinum porphyrin composite of a polyester foil that allows the gas molecules to pass through. The surface is coated with a black light-blocking material to prevent the interference of sunlight and other fluorescent substances in the water.

The blue light illuminates the fluorescent material and causes it to excite and emit red light. Since oxygen molecules can take away energy (quenching effect), the time and intensity of the excited red light is inversely proportional to the concentration of oxygen molecules. By measuring the phase difference between the excitation red light and the reference light, and comparing with the internal calibration value, the concentration of oxygen molecule can be calculated. After linearization and temperature compensation, the final value is output.

2: The polarographic sensor consists of a silver anode and a gold cathode with a ring at the bottom. A thin semi-permeable film, spread over the sensor, can isolate the electrode from the outside while allowing gas to enter. The bottom of the sensor is filled with a small amount of surfactant electrolyte to enhance wetting during operation.

When a polarization voltage is applied to the electrode of the polarographic sensor, oxygen penetrates the membrane and reacts at the cathode, generating a current.

 

 

2.Feature

 

• No electrolyte is required and will not be polarized.
• No oxygen consumption, not affected by flow rate.
• Built-in temperature sensor, automatic temperature compensation.
• Free from interference by chemicals such as sulfides
• Small drift, rapid reaction, more accurate measurement.
• Long service cycle, lower cost of use.
• Simple replacement of fluorescent cap.
• Rs-485 interface, Modbus/RTU protocol.
• Low power consumption,anti-interference.

 

3.Technical Specifications

 

Model	KFDO601
Measuring principle	Fluorescence method
Range ability	0~20mg/L (0 ≤ 200% saturation)
Resolution ratio	0.01mg/L,0.1℃
Precision	±2%F.S.,±0.5℃
Temperature compensation	Automatic temperature compensation(Pt1000)
Output mode	RS-485 bus, Modbus-RTU protocol
Working conditions	0～45℃,<0.2MPa
Storage temperature	-5～65℃
Installation mode	Immersion mounting
Cable length	5 meters, other lengths customizable
Power dissipation	＜0.3W@12V
Source	12～24VDC ±10%
levels of protection	IP68
Calibration	Two-point calibration
Fluorescent cap life	Guaranteed use for one year (under normal use)
Sensor shell material	POM and 316L stainless steel

4.Dimensional Drawing

Note:The sensor connector is m16-5 core waterproof connector male.

 

5.Installation and Electrical Connection

 

5.1 Install

 

 

The sensor shall be installed fixedly below the liquid level. The installation and use shall avoid collision or scraping against the surface of the fluorescent film head. The fluorescent film head part shall avoid being attached by the bottom sediment.Remove the rubber cover when use.

5.2 Electrical connection

• Red wire-power cord(12～24 V)
• Black wire-ground wire(GND)
• Blue Line-485 A
• White Line-485 B

Check wiring sequence carefully before power on to avoid unnecessary losses caused by wiring errors.

Wiring instructions: Considering that the cables have been immersed in water (including seawater) or exposed to air for a long time, all wiring positions are required to be waterproof, and the cables should have certain corrosion resistance.

 

6.Maintenance

 

6.1 Maintenance Schedule and Methodology

6.1.1 Maintenance Schedule

Different from the dissolved oxygen probe technology of electrochemical principle, the fluorescence dissolved oxygen probe does not consume oxygen and does not need to be cleaned frequently (except when it is used in viscous liquid).

Maintenance Task	Recommended Maintenance Frequency
Cleaning sensor	Wash every 30 days
Check for damage to sensors and fluorescent caps	Check every 30 days
Replace the fluorescent cap	Replace it once a year
Calibrate sensors (if required by the competent authority))	According to the maintenance schedule required by the competent department

Note: The maintenance frequency in the above table is only recommended, and the maintenance personnel shall clean the sensor according to the actual use of the sensor; however, the replacement frequency of the fluorescent cap is recommended once a year.

6.1.2 Maintenance Method

a) Sensor outer surface: clean the outer surface of the sensor with tap water, if there is still debris residue, wipe with wet soft cloth, for some stubborn dirt, you can add some household washing liquid to tap water to clean.

b) Surface of fluorescent film head: If there is dirt on the surface of fluorescent film head, please rinse with clean water or wipe gently with a soft cloth.Pay attention to the intensity of cleaning to avoid causing scratches in the measuring area and affecting the measurement accuracy.

c) Inside the fluorescent film head: it is generally unnecessary to clean. If water vapor or dust enters into the fluorescent film head, the cleaning steps are as follows:

• Screw down the fluorescent film head;
• Rinse the inner surface of the fluorescent film head and the optical window of the sensor.
• For oily dirt, you can use household cleaning solution;
• Gently dry the water with a clean flannelless cloth and let dry;
• Reinstall the fluorescent film head.

d) Check the cables of the sensor: there should be no damage to the skin and root of the cables;Terminals should not be submerged in water;When the sensor is normally installed, the cable should not be tensioned, otherwise the internal wire of the cable will easily break and the sensor cannot work normally.

e) Check whether the casing of the sensor is damaged by corrosion or other causes.

f) Daily storage of fluorescent film head: When not in use, a rubber protective cover with a wet sponge should be covered to keep the surface of the measuring area of fluorescent film head wet.If the surface of the measuring area of the sensor fluorescent film head is chronically dry, measurement error or data instability will occur, and it shall be soaked in water for 48 hours before use.

6.2 Frequently Questions

Wrong	Probable Cause	Solution
The operating interface cannot connect or does not display the measurement results	Error connecting controller to cable	Reconnect the controller and cable
	Cable failure	Please contact us.
	The fluorescent cap is not tightened or damaged	Refit and tighten the fluorescent cap or replace the fluorescent cap.
The measured value is too high, too low, or the numerical value remains unstable.	The outer surface of the fluorescent cap is attached to the outer object	Clean the outer surface of the fluorescent film head and agitate the film head during measurement.
	The fluorescent cap was damaged	Replace the fluorescent cap
	The fluorescent cap has exceeded its service life
Temperature measurements change slowly.	The temperature measuring area (stainless steel housing) is attached to the exterior	Gently brush the attachment with a soft brush

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

6.3 Calibration of Sensors

a) Zero Calibration

Weighing 5 g of sodium sulfite by a balance, adding 95mL of water into a 250-mL measuring cylinder, pouring the water into a beaker, adding the sodium sulfite which has been weighed, stirring with a glass rod, dissolving, and obtaining a solution of 5% sodium sulfite, putting the sensor in a solution, And the zero point calibration is carried out after the three-minute numerical stability is stable. Refer to the Appendix to the instructions

b) Slope Calibration

The sensor probe is placed in air saturated water and the slope is calibrated after 3 minutes of numerical stability. The instructions refer to the appendix.

c) Preparation of Air Saturated Water: add 2% 3 volume fresh distilled water to the constant temperature water bath to float the porous plastic sheet on the water surface (see figure below). At the same time, the bubbler (air pump) is used to aerate the water continuously for more than 1 hour, stop aeration, and get air saturated water after 20 minutes or so. Put the sensor into the water and calibrate the slope after the numerical value is stable.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Note: as an option, slope calibration can also be performed in water-saturated air. Put the sensor in a calibration bottle with a small amount of water (the probe is higher than the water surface 2-3mm) to ensure that the sensor film cap remains wet but has no water droplets, and the calibration slope is calibrated after 3 minutes of numerical stability.

6.4 Points for Attention

• Avoid sun exposure to the inner surface of the fluorescent cap.
• Please don't touch the fluorescent film with your hands.
• Measuring and calibrating the surface of fluorescent film to avoid attaching bubbles.
• Avoid directly applying any mechanical stress (pressure, scratches, etc.) to the fluorescent film in use.