DOC-0171 Rev G-9
2 6
© 2017 DROPLET MEASUREMENT TECHNOLOGIES
7.1 SP2-D: Procedure to Calibrate the Laminar Flow Element
1.
Disconnect the proportional valve by unplugging the control board’s J16 connector.
2.
Connect a DVM to TPL22 (Ashcroft) and to the ground test point, TPL17 (GND).
3.
Connect a bubble flow meter or volume-displacement flow meter to the sample inlet line
on the SP2.
4.
Start the SP2 data system, software, analyzer chassis power and sample pump—
DO NOT START THE YAG LASER!
5.
Take a series of readings with the bubble flow meter, over the range of 30-200 cc/min
nominally. For each of these readings, record the voltage shown on the DVM (for best
accuracy, average together 3-5 readings at each setting). Change the flow by manually
adjusting the needle valve, which is in parallel with the proportional valve.
6.
With this data, make a linear regression, with the flow rate on the Y-axis and the voltage on
the X-axis. This should be very linear, with a
slope
of about 90 (+/-20) and an
intercept
close
to zero (+/-5).
7.
In the SP2 software, click on the
Config
tab and the
Analog In
sub-tab. (This may require a
password.) In the
AI Channels
table, find the
Offset
and
Linear
parameters for
Sample
Flow.
These should read -1.1819 and 110.3629, respectively. Insert the value for
intercept
in the
Offset
field and the value for
slope
in the in the
Linear
field.
8.
Shut down the SP2 sample pump, data software, and the analyzer chassis.
9.
Reconnect the proportional valve cable at J16.
7.2 Procedure for Alignment of the YAG Laser
For complete instructions on aligning the laser, see DMT
DOC-0229: SP2 Laser Alignment Manual
.
7.3 Cleaning the Laser Optics
The optics used in the SP2 have reflectivity of 99.97% or better, and it is very difficult to clean them
without damaging or further contaminating the optics. If the laser power drops and it cannot be
recovered by a minor alignment, and other parameters such as the pump laser power are verified,
it is worth trying to clean the optics to recover laser power. Most likely the contamination will be
on the surface of the coupler and this should be cleaned first. A full alignment system will be
required to replace the coupler and get the YAG laser operational. It is also recommended that a
replacement coupler be available; if the unit cannot be cleaned, it will need to be replaced. See
DOC-0229, which gives information about optical cleaning and alignment of the YAG laser.
