Endress+Hauser Memosens COS81E, Руководство по эксплуатации

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Commissioning Memosens COS81E
22 Hauser
7.2.1 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
• Spot cap replacement
7.2.2 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 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 adjustment time of 30 min - 40 min for the zero-point gel COY8 elapsed?
• Is the value displayed plausible?
1. If the sensor signal is stable:
Calibrate the zero point.
2. If necessary:
Adjust the sensor to the zero point.
If the oxygen sensor is calibrated too early, this can result in an incorrect zero point.
Rule of thumb: operate the sensor for at least 30 min in the COY8 zero-point gel.
Follow the instructions in the kit documentation enclosed with the COY8 zero-point
gel.
7.2.3 Calibration in oxygen with 100% rH
1. Activate the hold status at the transmitter.
2. Remove the sensor from the medium.
3. Clean the outside of the sensor carefully with a damp cloth.
4. Suspend the sensor just above the surface of the water.
Do not immerse the sensor.
5. Allow a temperature compensation time of approx. 20 minutes for the sensor in the
ambient air. Make sure that the sensor is not exposed to any direct ambient effects
(direct sunlight, drafts) during this time.