Manual, Ultra High Sensitivity Aerosol Spectrometer (UHSAS)
DOC-0210 Rev E-4
3 3
© 2017 DROPLET MEASUREMENT TECHNOLOGIES
to describe the response of the flow controller. The parameters can be changed to
accommodate other gases. Consult DMT for instructions or revised calibration parameters.
6.0
Safety Procedures and Troubleshooting
6.1 Safety Procedures
CAUTION:
Do not operate laser with instrument cover off.
This unit is equipped with a laser safety interlock system. Whenever the cover is removed, 2
mechanical switches are activated. The first turns off the AC power to the laser control module
that supplies power to the laser. The second one disables the laser enable line. Under no
circumstances should the user disable these safety interlocks. The laser should remain off any
time the cover is removed. All safety precautions noted on caution labels should be adhered to.
6.2 Troubleshooting
DMT advises users periodically to perform a zero count test and check the instrument Reference
level displayed on the
Controls
tab. These tests and checks should be performed at least once a
week to confirm the instrument is functioning properly.
6.2.1
To perform a zero count:
•
Install the supplied zero-count filter to the inlet of unit.
•
Load a bin map of 55 to 154 nm, as this will help determine if the unit has a leak
or it is counting noise.
•
Run 5-minute samples. If you get more than a few counts, determine whether
these counts reflect noise or a leak. Noise will typically appear in only the first
few bins. If the unit has a leak, in contrast, typically there will be an ambient
distribution.
•
If the unit appears to have noise counts, check the
Reference
level on the
Controls
tab. The displayed Reference should be approximately 2.5 V; if it has
dropped by more than 25% (i.e., Reference < 1.88 V), clean the laser optics as
described in section 7.0.
•
If the unit appears to have a leak, check any external connections between the
unit and the filter. Then rerun the zero-count test.
•
If an acceptable background zero-count level cannot be attained, do a
recirculation check. On the
Configuration
tab, log on with a password to put the
system in calibration mode. On the
Map
tab, select time binning, click on the
G3
