Turbidity meters are essential tools for monitoring water quality in various industries, including environmental monitoring, wastewater treatment, food, and beverage. These meters measure turbidity for drinking and surface water. Calibration ensures the accuracy of turbidity measurements, providing reliable data for quality control. Here’s a step-by-step guide on how to calibrate your portable or benchtop turbidity meter effectively.

Step 1: Prepare the Equipment

Gather all the necessary equipment for calibration:

• Turbidity calibration standard solutions
• Cleaning solutions
• Clean, lint-free cloth
• Distilled water
• Calibration cuvettes
• Gloves

Step 2: Clean the Meter

Proper cleaning is crucial to remove any residue or contaminants that could affect the accuracy of the measurements. Use a clean, lint-free cloth moistened with cleaning solutions to wipe the optical surfaces of the meter carefully.

Step 3: Prepare Calibration Standards

Ensure that the calibration standards are within their expiration date and properly mixed before use. Follow the manufacturer’s instructions for dilution if necessary. It is recommended that the turbidity value of the prepared calibration solutions to be close to the default calibration points.

Warning: Handle hydrazine sulfate with care because it is a carcinogen reagent. Avoid inhalation, ingestion, or skin contact. Formazin solution can also contain some hydrazine traces.

Step 4: Zero Calibration

Zero calibration establishes the baseline reading when there is no turbidity in the sample. Place a clean cuvette filled with distilled water into the meter and adjust the instrument to read zero.

Step 5: Calibration with Standards

Low-Level Calibration: Insert the cuvette containing the low-level turbidity standard into the meter. Allow the reading to stabilize, then adjust the meter to the known turbidity value of the standard.

High-Level Calibration: Repeat the process with the high-level turbidity standard. Insert the cuvette containing the high-level standard and adjust the meter to the known value.

For best results, the measurement techniques must be followed during calibration. If formazin standards are used, mix the cuvettes gently for about 1 minute and then allow the standard to settle for 1 more minute before calibration. Calibration can be performed in two, three four or five points. Calibration of the turbidity range will not affect the free or total chlorine measurements. Before making the calibration, be sure that you are in the correct range.

Step 6: Verification

After calibration, it’s essential to verify the accuracy of the measurements. Use a different instrument or test the samples in a laboratory for comparison. If there are discrepancies, recalibrate the turbidity meter and verify again until the readings are consistent.

Step 7: Documentation

Document the calibration process, including the date, standards used, and any adjustments made. Keep records of calibration for regulatory compliance and quality assurance purposes.

Step 8: Routine Maintenance

Regular maintenance is the key to keeping your turbidity meter in optimal condition. Clean the instrument after each use and follow the manufacturer’s recommendations for calibration frequency and any other maintenance procedures.