Turbidity and COD sensors are optical instruments. Customers usually notice errors when the optical window is dirty, bubbles remain on the measuring area, or the sensor is too close to the container bottom or wall.

Short Answer

Keep optical windows clean, avoid bubbles, maintain enough distance from container surfaces, and calibrate with the correct zero and slope standards. For COD sensors, calibrate turbidity first, then perform COD calibration.

Turbidity Sensor Calibration Basics

For zero-point calibration, place the sensor vertically in a zero-turbidity solution and keep the probe tip at least 10 cm from the bottom of the beaker. Wait 3 to 5 minutes until the value stabilizes. For slope calibration, use the proper standard solution and again wait for stability.

Shake the standard solution evenly before calibrating. Uneven standards can make the calibration value unreliable.

COD Sensor Calibration Order

When calibrating COD, the turbidity part of the COD sensor should be calibrated first, followed by COD calibration. For COD zero-point calibration, a 5 mg/L COD solution may be used. For slope calibration, a 100 mg/L COD solution may be used.

During COD calibration, the optical paths must be fully submerged by more than 2 cm and must be free of bubbles.

Cleanliness Is Measurement Accuracy

The measurement window and quartz plates must be clean and free of foreign matter. Mud, fingerprints, algae, oil film or air bubbles can all change the optical signal.

Use clean water and a lint-free cloth for gentle cleaning. Do not scratch the window. In field water with high suspended solids, inspect the window more often.

Installation and Field Precautions

Keep turbidity probes at least 100 mm from the bottom and walls during testing. Avoid fluorescent containers or environments that can interfere with optical measurement. If water flow is rapid, fix the COD sensor securely to avoid impact damage.

Never suspend the sensor by the cable. The cable connector must remain secure, and the cable should not be under tension.

Related YexSensor PDF Guides

For calibration commands and model-specific handling notes, see the Water Quality Sensor Calibration and Usage Precautions PDF and the Water Quality Sensor Usage and Maintenance Instructions PDF.

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