25
Startup
Preparing for Measurement
For checking the background a setup for the appropriate capillary must be loaded or generated. The
dilution factor must be set to 1 since only filtered CASY ton is used for measuring the background.
In addition, the cursor positions should be set to the scale limits to detect all potentially contaminat-
ing particles.
Depending on the measuring capillary used, the background should not exceed the following val-
ues:
150 µm measuring capillary:
<100 Counts/ml
60 µm measuring capillary:
<200 Counts/ml
45 µm measuring capillary:
See instructions on how to use the 45 µm measuring capillary.
Too high a background may result from impurities in your CASY ton or not having used a new CASY
cup. Filter the CASY ton through a particle filter . The pore size of the particle filter should normally
be ≤ 0.8 μm. If you use the 45 μm capillary, then the pore size should be ≤ 0.45 μm. Use a new CASY
cup for every measurement. Repeat steps 1 to 5 with freshly filtered CASY ton. If the system fails to
become clean even after several attempts, you should carry out the
Weekly Cleaning Routine
(see
Chapter 4.1). If this exercise fails to produce the desired result, please check that the location of
your CASY System satisfies the criteria indicated in Chapter 3.1.
You must ensure that all the vessels used to prepare the samples, the CASY ton used to flush the
system and dilute the samples and also any CASY cups used are
free of grease and particle im-
purities
. For routine preparation of the measuring samples, use a dispenser (10 ml) with a particle
filter wherever possible.
To avoid incorrect measurements, CASY cups should be used once only.
Instructions on how to use the 45 µm measuring capillary:
The 45 µm measuring capillary has been optimized for microbiological applications. A special process
for signal detection is used to ensure that very small cells near the system’s physically determined
lower measuring limit are reliably recorded. This process works reliably from a
minimum concen-
tration of 20,000 cells/ml
upwards. The background displayed when running empty with filtered,
degassed CASY ton (up to 3000 counts/ml) is of no consequence for measurements above the
minimum concentration.
For measurements using the 45 µm measuring capillary
CASY ton must be degassed on a regular
basis
. Owing to the higher capillary resistance and the higher measuring vacuum, failure to degas
may lead to false measuring results due to gas bubbles being present in the capillary. Storing the
CASY System and the used CASY ton at constant temperatures as well as ensuring that the CASY ton
is
never stored cold
will lower the necessity to degas CASY ton permanently. To degas the CASY
ton, use an ultrasonic bath and a vacuum pump (suction cylinder with water jet pump). Degas for at
least 10 minutes to guarantee fault-free measuring operation.
