Hach ORBISPHERE 3658 Basis-Benutzerhandbuch Seite 18

Calibration
Method
Liquid CO solution
2
Gas at atmospheric
pressure
Gas at elevated
pressure (2-3 bar)
Before calibrating check that the sensor membrane surface is tight, smooth and wrinkle free. Select
the gas measurement phase for calibration (for full details see
Next, select the calibration medium using the Hach 3658 program (see
on page 17).
Ensure that normal measurement mode is selected in the Measurement Mode menu of the Hach
3658 program (see Measurement mode
Calibration must only be carried out once the TC sensor is giving a stable measurement. Expose the
membrane to the calibration sample until this stable reading is obtained. This usually takes about
5 minutes.
For calibration it is important that the sensor's membrane is at the same temperature as the
calibration sample. Therefore, allow some sample to pass through the flow chamber for 3 minutes
before calibrating.
6.2.1 Using the high precision calibration kit
Using the ORBISPHERE High Precision Calibration Kit, calibration and validation of the instrument
can be carried out quickly and easily. This ensures that each measurement of dissolved CO
true and accurate reading which is essential to final product quality.
In short these calibration kits offer:
• Traceable and accurate calibration
• Quick and easy solution preparation
• Eliminates handling of aggressive chemicals which are usually required in reference preparation
• High and low level kits are available to ensure accuracy in the appropriate measurement range
Once the solution has been prepared in the calibration bottle, it can be used in the standard package
piercer in place of the sample package.
6.2.2 Using a source of pure CO
Ensure that the purge cycle is running correctly by placing the purge gas exit tubing into water. This
rate should be more than four bubbles during the purge which lasts for 4 seconds. This purge cycle is
repeated every 20 seconds.
18 English
Table 1 Sensor calibration information
Time Benefits
5 min High accuracy (for
liquid analysis)
5 min Quick and easy
10 min Higher accuracy than
atmospheric method.
Validation of the
sensor linearity
on page 17).
gas
2
Drawbacks
Sensor linearity
validation not
possible
Less accurate than
other methods
Requires a certified
pressure gauge
Gas measurement phase
Calibration medium
Reference
ORBISPHERE High
Precision Calibration
Kit
Gas with known purity,
certified barometer
Certified pressure
gauge
on page 16).
gives a
2