COD Automatic Online Monitor

The COD Automatic Online Monitor is a high-performance analytical instrument specifically designed for real-time monitoring of chemical oxygen demand (COD) in water. It adheres to national standards and features high accuracy, stable operation, and easy maintenance, making it an ideal choice for water quality monitoring in industrial and municipal scenarios, which is also widely used in online COD monitoring of industrial wastewater and municipal sewage discharge.

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Performance Features

Selector Valve Assembly

It controls the reagent sampling sequence with flexible channels and versatile functions. It boasts advantages such as small volume, easy maintenance, and long service life.

Sampling Assembly

A peristaltic pump is adopted for negative pressure suction, and there is always an air buffer zone between the reagent and the pump tube, which avoids corrosion of the pump tube. Meanwhile, it makes reagent mixing more simple and flexible.

Metering Assembly

The visual photoelectric system realizes precise reagent metering, overcoming the quantitative error caused by the wear of the peristaltic pump tube. At the same time, it achieves accurate quantification of trace reagents, with each dose being only 1.5 ml, greatly reducing reagent consumption.

Sealed Digestion Assembly

The high-temperature and high-pressure digestion system accelerates the reaction process and overcomes the corrosion of the equipment caused by the volatilization of corrosive gases in the open system.

Reagent Tube

Imported new PTFE transparent hoses are used, with an inner diameter of more than 1.5 mm, which reduces the probability of blockage by water sample particles.

Working Principle

The water sample is delivered through a peristaltic pump and a nine-way valve. Under the action of digestion solution and acid solution, the mixture of water sample, potassium dichromate solution, mercuric sulfate solution (mercuric sulfate can eliminate the interference of chloride ions in the water sample, because chloride ions can form very stable mercuric chloride with mercury ions), and silver sulfate solution (silver sulfate is added as a catalyst to oxidize straight-chain aliphatic compounds more effectively) is heated to 165℃. After dichromate ions oxidize the organic matter in the solution, the color changes. The analyzer detects this color change and converts it into a COD value for output. The amount of consumed dichromate ions is equivalent to the amount of oxidizable organic matter.

Technical Specifications

Item	Specification
Method Basis	National Standard GB11914-89 "Water Quality - Determination of Chemical Oxygen Demand - Potassium Dichromate Method"
Measurement Range	0-15000 mg/L COD (Extendable)
Accuracy	When ≥100mg/L, no more than ±10%; When <100mg/L, no more than ±8mg/L
Repeatability	When ≥100mg/L, no more than ±10%; When <100mg/L, no more than ±6mg/L
Indication Error	No more than ±10%
Measurement Cycle	50 minutes; Digestion time can be adjusted arbitrarily from 5 to 120 minutes according to actual water samples
Sampling Cycle	Time interval (adjustable arbitrarily from 55 to 9999 minutes) and on-the-hour measurement mode
Calibration Cycle	Adjustable at any interval from 1 to 99 days and at any time
Maintenance Cycle	Generally once a month, about 30 minutes each time
Output	4~20mA (2 channels), RS232, RS485
Relay Output	2 control relay outputs
Environmental Requirements	Indoor with adjustable temperature, recommended temperature +5～28℃; Humidity ≤90% (no condensation)
Power Supply	AC220±10% V, 50±10% Hz, 5 A
Dimension	800 mm (H) × 430 mm (W) × 300 mm (D)
Others	1. Abnormal alarm and power failure will not lose data; 2. Touch screen display and command input; 3. After abnormal reset and power recovery, the instrument automatically discharges residual reactants inside and resumes work automatically.

For more information about the COD Automatic Online Monitor or to place an order, please feel free to contact us. Our professional team will provide you with high-quality services.

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