DOC-0171 Rev G-9
2 8
© 2017 DROPLET MEASUREMENT TECHNOLOGIES
9.0
Troubleshooting
Problem
Possible Cause
Solutions
After a few minutes of
running, the actual
sample flow does not
match the set sample
flow.
Exhaust bypass valve
set incorrectly. No purge
or sheath flows.
If the sample flow is significantly off (several
hundred ccm), the problem could be in the sheath
and purge flows. Check the sheath and purge
flow readings compared to the sheath and purge
flow set points. If they are low, the sample flow
will not regulate and be high. Check operation of
the pressure side of the sample pump. Cracked
pump diaphragm, kinked, plugged, or
disconnected purge line. Check the Exhaust
Valve Set voltage. If this is zero and the flow is
high, the needle valve is too far open and must
be closed to bring the proportional valve into
regulation. If the Exhaust Valve Set voltage is 5V
and the flow is low, the needle valve is closed too
far and needs to be opened. See the flow system
section of the manual for setting of these valves.
Large burst of high-
concentration aerosol
particles have
contaminated the
instrument and the
laser power has
dropped significantly.
Rapid over-
pressurization of the
chamber.
IMMEDIATELY turn off the laser. If possible, put
a filter on the front of the instrument, and allow to
purge for 30-60 minutes. After this time turn the
laser on, and check laser power. If it is nearly to
the level before the contamination, allow the SP2
to operate. If not, purge for additional time.
Contact DMT if the laser power does not recover.
The instrument has
been started, but no
particles are seen on
the display.
Laser off or no sample
flow.
Check that the laser has not shut off. Check that
the sample flow is positive. Check the laser
interlocks are engaged (i.e., depressed).
Sample pump does not
start when the PUMP
switch is turned on.
Pump head pressure
not bled down.
If the pump has just been turned off, the head
pressure in the purge side may be too high to
allow the pump to start. Otherwise check the
pump fuse on the back of the analyzer chassis.
Sample flow oscillates
more than +/- 1 ccm.
Pressure fluctuations in
the inlet line. A 0.5 in
water pressure
transducer is used on
the LFE in the inlet The
unit is very sensitive to
pressure noise.
Check if pressure fluctuations are present in the
inlet. At the startup, it can take several minutes
for the flow to stabilize. Also, if there are pressure
perturbations in the inlet, it can take a minute or
more for the pressure to stabilize.
