08354B DCN7877
Teledyne API T640 PM Mass Monitor
66
IMPORTANT
The Particle Sensor PMT Adjustment uses our SpanDust™, a
monodisperse dust with a specific refractive index. All T640
instrument PMTs have a very specific response to this span dust
which allows for the sensor to be checked and adjusted in the field
for drift caused by contamination of the optics.
NOTE
This is not a calibration of the optical sensor based on the mass of
dust being used, but simply a mechanism to check and adjust the
PMT response to particles with a specific and known refractive index.
1. Navigate to the PMT Adjust screen.
2. Remove the T640 sample inlet or the 640X Option sample inlet and press the
Start button on this screen to suspend normal data acquisition and start this
adjustment process.
3. Prepare the SpanDust™ bottle by uncapping the “air intake” at the bottom of
the silica gel drier attached to the bottle.
4. Place the tube from the SpanDust™ bottle into the top of the Upper Inlet Tube
for the instrument.
5. Ensure that the silicone tube fits snugly inside the aluminum inlet tube, and do
not allow the bottle to hang, as it could dislodge the silicone tube from the inlet
tube.
6. Gently tap the SpanDust™ bottle to barely agitate the contents just enough to
allow the dust to be pulled into the sensor, and allow 30 seconds for the Peak
Channel reading in this screen to respond.
7. Note the Peak Channel value written on the SpanDust™ bottle. The typical
value is 11.1 (
IMPORTANT: use the value displayed on the SpanDust™ bottle
label with +/- 0.5 channel tolerance
), which will be used for example purposes
below. If the bottle being used has a different peak value, follow the same
procedure with the goal of peaking at that value.
8. If the Peak Channel reading is not at ± 0.5 compared with the value displayed
on the SpanDust™ bottle, then adjust the PMT Setting by pressing the Peak
Adjust left (decrement) or right (increment) buttons to center the Peak voltage.
Each press of a button is 1 volt, so press the Peak Adjust button by as many
times as the number of volts the reading is off.
9. Allow 30 seconds for the Peak Channel reading in this screen to respond, and
if it is not at ± 0.5 (of the value displayed on the SpanDust™ bottle), repeat the
process. This could take several tries over a long period when conducted in a
humid environment.
10. Once the Peak Channel reading is at ± 0.5 of the value displayed on the
SpanDust™ bottle, reattach the sample inlet and press the Stop button to stop
the adjustment process and resume normal data acquisition.
Summary of Contents for T640
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