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Installing and Calibrating an Aperture Tube
Using Small Aperture Tubes (20 µm and 30 µm)
4. Fill the clean beaker with clean or pre-filtered ISOTON® II or de-ionized water (see Pre-Filtering
the Electrolyte and Cleaning Fluid, page 3-5). Make sure that the fluid level is higher than the fluid
level during the previous run.
5. Lift the beaker to immerse the aperture tube and electrode in the beaker’s filtered liquid. Swish
to remove remaining particles.
6. Place the beaker on the platform below the Aperture Tube and allow remaining liquid to drip
into the beaker.
Figure 3.3 illustrates how to use a squeeze bottle filled with clean or pre-filtered ISOTON® II to clean
an Aperture Tube. This is a convenient cleaning method that can be used to supplement the beaker
immersion cleaning method.
Figure 3.3 Cleaning an ST Aperture Tube with a Squeeze Bottle
Small Aperture Noise Profiles
The images below illustrate a typical noise profile obtained using a clean system, and a noise profile
obtained using a system that requires additional cleaning.
The noise profile obtained using a clean Analyzer system (Figure 3.4) shows a background count
primarily in the region between 0.4 and 0.5 µm. Some background noise remains when using small
apertures.
The noise profile obtained using an Analyzer system that has not been properly cleaned (Figure 3.5)
shows a high background count due to system contamination.
Both profiles were obtained using a 20 µm ST Aperture Tube and filtered ISOTON® II. Runs were
completed in time mode (30 seconds) with current set to 600 µA and gain set to 4. For information
on current and gain settings appropriate for small apertures, see page 3-28.
PN A51387AB
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