Field adjustment parameters - PR53 - PR53AC - PR53AP - PR53GC - PR53GP - PR53M - PR53SD - PR53W

PR53 Series User Guide

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User guide

The field adjustment can be calculated with the following pattern: Adjusted concentration = Raw concentration × Field gain + Field offset

Each concentration curve has its own field adjustment. If you change the concentration curve, field adjustment is no longer the same.

Accurate calibration is only achieved if the sample is taken correctly. Pay special attention to following details:
  • Field adjustments are used to cancel out any inaccuracy of the concentration model, or process condition related factors. The field sample values must be taken from the particular unit that is to be adjusted, not from a laboratory unit, for example.
  • The sampling valve and the refractometer should be installed close to each other in the process.
    WARNING Wear protective clothing appropriate to your process when operating the sampling valve and handling the sample.
  • Run the sample before starting to collect data points to avoid sampling old process liquid that has remained in the sampling valve.
  • Read the raw concentration value at exactly the same time with sampling.

    The easiest way of doing this is to use the Field sample feature. The value of each sample is the average of 10 consequent measurements to increase accuracy and reduce possible process noise.

  • Use a tight container for the sample to avoid evaporation.
Offline calibration using process liquid very seldom gives reliable results, as problems are caused by:
  • Low flow which makes sample to form an unrepresentative film on the prism
  • Sample evaporation at high temperature or undissolved solids at low temperature giving deviations from laboratory determinations
  • An aging sample which is not representative
  • Outside light reaching the prism