Endress+Hauser Memosens COS81D, Operating Instructions Manual

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Calibration and adjustment Memosens COS81D
22 Hauser
7 Calibration and adjustment
The sensor is calibrated and adjusted in the factory prior to delivery and is therefore ready
for immediate use.
Calibration or adjustment is required in the following situations:
• Changes due to process conditions, e.g. for Cleaning in Place (CIP), Sterilization in Place
(SIP) and autoclaving
• Changes due to stress: temperature and/or chemicals (cleaning)
• Following a spot cap replacement
Recommended procedure after replacing a spot cap
First calibrate and adjust the sensor at the zero point and then in the presence of
oxygen. Alternatively, you can enter the spot cap calibration data provided directly at
the transmitter.
Calibration and adjustment can also be monitored or renewed cyclically (at typical time
intervals, depending on operating experience), e.g. within the context of system
monitoring.
7.1 Types of calibration
The following types of calibration are possible:
• Zero point
• Single-point calibration in nitrogen or COY8 zero-point gel
• Numeric input
• Point at oxygen
• Air, water vapor-saturated (recommended)
• Air-saturated water
• Air, variable
• Test gas calibration
• Numeric input
• Sample calibration
• Fermenter scaling
• Temperature adjustment
7.2 Zero point calibration
The zero point is not so important when working with relatively high concentrations of
oxygen. In this type of application, a zero point calibration is required only after the spot
cap has been replaced.
However, once oxygen sensors are used at low concentrations and in the trace range, they
must also be calibrated at the zero point.
Zero point calibrations are demanding as the ambient medium - usually air - already has a
high oxygen content. This oxygen must be blocked off for zero point calibration of the
sensor.
A calibration with zero-point gel COY8 can be used for this purpose:
The oxygen-depleting gel COY8 (→  35)creates an oxygen-free medium for zero point
calibration.
Prior to sensor zero point calibration, check the following:
• Is the sensor signal stable?
• Has the compensation time of 30 min - 40 min elapsed?
• Is the value displayed plausible?
1. If the sensor signal is stable:
Calibrate the zero point.