KROHNE OPTISYS TUR 1050 EN - Manual (Page 33)

OPERATION
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OPTISYS TUR 1050
www.krohne.com 11/2012 - 4002444301 MA OPTISYS TUR 1050 R02 en
5.6.3 Calibration procedure (offset calibration)
Under certain circumstances an offset calibration is more suitable than a physical calibration as
described in the previous chapter. This might be the case if the process application contains a
number of devices so that a regular physical calibration is not possible.
The maximum offset value is ±1 NTU/FNU. If the deviation goes beyond this value, a physical
calibration is necessary. An offset calibration always starts with a comparison of samples:
• Collect a grab sample of the process water with the optional grab sample cuvette.
• Measure the turbidity with the help of the device.
• Take a second grab sample and measure its turbidity using a turbiditymeter for laboratory use
(the manufacturer's service department can give you examples of suitable devices).
• Compare the turbidity values of both samples. If they are very close, then an offset calibration
is not required and you can stop the procedure at this step.
If both samples differ substantially (but less than 1 NTU/FNU), continue with the actual offset
calibration. The following steps make the turbidity reading of the device agree with the value of
turbidity meter for laboratory use:
• In the normal measuring mode (AUTO), press the button MODE/EXIT twice.
i The device switches in the configuration mode and the arrow in the display appears in front
of "CONFIG".
• Press ^ several times until "OFST" appears in the lower row of the display.
i While the lower row shows"OFST", the upper row indicates the status of the offset function
("ON" or "OFF", default setting is "OFF")
• Change the status of the offset function by pressing ↓ or ↑, see following drawing.
INFORMATION!
Be aware that an offset calibration does not offer the accuracy of a physical calibration. An offset
calibration makes the device accurate only at turbidity levels in the immediate vicinity of the grab
sample's value and not in the full measuring range!