What does the slope percentage indicate after a calibration on an IntelliCAL™ LDO101 Luminescent/Optical Dissolved Oxygen Probes?

Document ID

Document ID TE3947

Published Date

Published Date 10/09/2019
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Question
What does the slope percentage indicate after a calibration on an IntelliCAL™ LDO101 Luminescent/Optical Dissolved Oxygen Probes?
Summary
Slope percentage on LDO.
Answer
This probe has a factory calibration slope specific to the senor cap lot that is stored on the iButton. When a calibration is complete and sucessful a slope percentage will be displayed. This slope value is calculated by comparing the slope of that calibration to that of the factory calibration. The slope is calculated by the mg/L reading on 100% DO from a user calibration, divided by the factory calibration curve for the mg/L DO reading on 100% DO at the same temperature and pressure. A slope that is more than 105% or less than 95%  is not the same as a 5% error. Instructions for performing an accuracy check can be found here: How can the IntelliCAL™ LDO101 electrode accuracy be checked?

It is not an indication of electrode accuracy, but is instead an indication of sensor cap condition. The sensor cap should be replaced once per year. If a slope out of range message is displayed after a calibration, that is an indication that the sensor cap needs to be replaced, even if it's before the year is up. Damage to the sensor cap or interaction with agressive or abrasive samples can lead to degredation at an excellerated rate, the slope percentage and sensor cap age can be helpful in judging the rate at which this degredation is occuring.

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