Water Quality & Calibration

Generally it is recommended that calibration is performed and checked daily or before use. When data accuracy is crucial, for compliance requirements or when results are questionable, calibration frequency and verification of the system response becomes more imperative.

At Rice, we carry solutions, standards and accessories:

  • pH Buffers
  • Conductivity Standards
  • ORP Standards
  • Electrode Care Solutions
  • Dissolved Oxygen Solutions
  • Calibration Accessories


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pH

  • It is a known fact that pH electrodes must, from time to time, be calibrated to maintain measurement accuracy. How often you need to calibrate your electrode varies considerably with each application and its unique conditions. Your data is only as good as your calibration and the only way to ensure the system is providing accurate data is to check response in a buffer with a known pH value. Electrode care & maintenance are also an essential part of data quality and reliability in the field.

Conductivity

  • Conductivity meters and cells should be calibrated to a standard solution before using. Select a standard that is closest to the conductivity of the solution to be measured. Conductivity measurements are temperature dependent. The degree to which temperature affects conductivity varies from solution to solution. Conductivity sensors are not subject to much wear, but are very contamination sensitive. Therefore, calibration has to be performed very carefully to avoid incorrect measurements. Conductivity standards may only be used once; the sensor has to be cleaned first and moistened with standard to avoid the displacement of any possible adhering residues of sample or distilled water.

Dissolved Oxygen

  • Calibrate the DO sensor regularly. Dissolved oxygen is affected by water vapour saturation and temperature. Calibration should be performed in an area of constant temperature. Ambient air (100%) can be used as the standard, a moist (never wet) sponge in a calibration beaker creates a water vapour-saturated atmosphere above the sensor surface. A zero solution is also available when low dissolved oxygen values are expected.

ORP

  • Calibration for ORP electrodes and meters is not as common as in pH, conductivity and other electrochemical measurements. Oxidation-Reduction Potential (ORP) or Redox measurements are based on displaying the response of a specialized electrode in a solution. Like pH electrodes, each ORP electrode has unique characteristics that cause variability in the signal the electrodes send to the meter. For most ORP applications, the absolute accuracy is far less important than the speed and relative changes measured in the system. Solutions are typically used to confirm if the electrode gives a response to ORP.