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What Is the Measurement Range of a COD Sensor? 
 Chemical Oxygen Demand (COD) is one of the most important indicators in water quality monitoring. It reflects the level of organic pollution in water and is widely used in environmental monitoring, wastewater treatment, and surface water management.

One of the most common questions from engineers and buyers is:
“What is the measurement range of a COD sensor?”

In this article, we will explain COD sensor measurement ranges, what affects them, and how to choose the right sensor for different water monitoring applications.

What Is the Measurement Range of a COD Sensor?

The measurement range of a COD sensor refers to the concentration range of organic pollutants that the sensor can accurately detect and measure, usually expressed in mg/L (milligrams per liter).

In general, COD sensor ranges vary depending on the application:

Low-range sensors: 0–50 mg/L (clean water, drinking water sources)
Standard-range sensors: 0–200 mg/L (surface water, rivers, lakes)
Medium-range sensors: 0–1000 mg/L (municipal wastewater, industrial effluent)
High-range sensors: up to 2000 mg/L or more (heavy industrial wastewater)

Choosing the correct range is critical because:

A too-low range may saturate in polluted water
A too-high range may reduce sensitivity in clean water

What Factors Affect COD Sensor Measurement Range?

Several technical factors determine how a COD sensor performs across different ranges:

1. Measurement Principle

Most modern COD sensors use UV absorption technology (typically at 254nm), which correlates organic matter concentration with light absorption.

2. Water Type

Different water bodies require different ranges:

Rivers & lakes → lower COD range
Sewage & industrial wastewater → higher COD range
3. Sensor Calibration and Algorithms

Advanced sensors can convert raw optical data into COD, BOD, and TOC estimates, improving versatility across ranges.

4. Optical Design & Stability

Sensor stability, drift control, and signal processing affect accuracy across the full measurement range.

How to Choose the Right COD Sensor Range?

When selecting a COD sensor, consider:

Expected pollution level of water
Monitoring environment (river, wastewater plant, seawater, etc.)
Required response speed
Maintenance frequency

For most engineering applications, a 0–1000 mg/L range COD sensor is the most flexible choice.

Recommended Solution: KNF-1008APro Intelligent COD Sensor

For users looking for a high-performance and wide-range COD monitoring solution, the KNF-1008APro COD Intelligent Sensor provides a reliable and advanced option.

It is designed for real-time water quality monitoring across multiple environments, including surface water, rivers, lakes, reservoirs, municipal sewage, and seawater.

Key Features
UV absorption method (254nm & 546nm dual wavelength)
Multi-parameter measurement: COD, BOD, TOC, turbidity
Wide measurement range:
COD: 0–200 / 1000 mg/L
Turbidity: 0–500 / 2000 NTU
BOD: 0–100 / 500 mg/L
TOC: 0–80 / 400 mg/L
Fast response time: <10 seconds
RS485 Modbus-RTU communication
Built-in cleaning brush for reduced maintenance
Data software included (calibration, analysis, diagnostics)