Maintenance, Service, and Troubleshooting 6-21
5. The upper insulator is pressed into the sheath cone to maintain good
alignment of the center rod therefore the insulator must be pressed out
from below by pushing on the Dacron screen. Orient the sheath cone
so that the sharp edge is pointed upwards. Place the cone in a press
and support it by the outer edges. Using a plastic dowel slightly smaller
than the inner diameter of the cone, push the Dacron screen from
below until the upper insulator comes free (about ¼ inch).
6. Remove the Dacron screen and visually inspect. If the screen is
damaged, replace it with a new screen. If the screen is undamaged but
dirty, continue with step 7.
7. Grip the dirty screen with tweezers and dip into a clean beaker filled
with IPA. Repeat three times.
8. Allow the screen to air dry, or dry it with a very light flow of filtered,
compressed air.
9. Replace the screen in the sheath cone.
10. Reassemble the DMA.
Performing ISO Zero Tests
ISO 15900, an international standard which provides methods for testing
and calibrating differential mobility devices, specifies a zero check for the
detector, the DMA, and the SMPS.
To perform a detector zero test, follow these instructions:
1. Disconnect the detector tubing from the Electrostatic Classifier so that
it is pulling in room air. Check that the detector is not reporting any
errors. If it is reporting an error, refer to the error descriptions in your
detector’s manual.
2. Verify that the detector is measuring a non-zero concentration.
3. Remove the high efficiency HEPA filter from the Accessory Kit. Using a
length of ¼-inch tubing, connect the filter to the detector inlet.
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