45
Performing and Evaluating Measurements
Points to be Observed when Performing Measurements
Air bubbles
The CASY System precisely monitors the incidence of “critical” air bubbles in the rising fluid column
within the vertical tube. Large air bubbles affect the accuracy of the sample volume measurement
and may therefore result in the cell concentration being measured incorrectly. If an air bubble ex-
ceeds a critical size during a measurement, the following error message appears:
ERROR SCREEN
TT-2AB-9999 15.04.2009 10:15
Large Air Bubble detected !
Regular use of CASY clean.
is recommended.
Further information will be
provided by your manual.
USE ENTER TO CONFIRM.
PRESS CLEAN TO FLUSH THE LIQUID SYSTEM.
If you observe the vertical tube in the inspection window at the front of the measuring unit, you will
be able to see the air bubble. If the air bubble rises to the fluid meniscus and disappears, it will not
affect subsequent measurements. You can repeat the measurement immediately after confirming
the error message by pressing
ENTER
. If, however, the air bubble remains suspended in the verti-
cal tube, you must remove it by replenishing the fluid system using the
CLEAN
flushing function.
Deposits within the fluid system sometimes become noticeable through frequent air bubble error
messages. If necessary, run a
Weekly Cleaning Routine
(see Chapter 4.1) to remedy the problem.
Ensure that the system is flushed thoroughly with distilled water to remove any remnants of CASY
clean.
If, during the measurement, only small air bubbles are evident within the vertical tube, no action
is necessary. Small air bubbles – which are higher in number with small measuring capillaries –
are caused by the process of electrolysis at the inner electrode. These are normal, no error message
is triggered and the measurement is not affected.
