TSI Instruments Sizer 3310A User manual

Introduction 1
Model 3310A
Aerodynamic Particle Sizer®
Installing the Sensor 2
Spectrometer
Description of the
Sensor 3
Instruction Manual Operating the APS 4
Particle Coincidence
and Count Variance 5
Maintaining and
Servicing the APS 6
Troubleshooting the
Sensor 7
Installing the
Microcomputer
System
8
Basic Software
Reference Guide 9
Operating Basic
Software 10
Calibrating the APS
System 11
Appendixes

Manual History
ii
The following is a manual history of the Model 3310A Aerodynamic
Particle Sizer®Spectrometer (Part Number 1933766).
Revision Date Revision Date
Final
A
B
C
D
E
F
New Vers.
A
October 1987
January 1988
July 1989
December 1989
April 1990
November 1991
February 1992
December 1992
March 1993
B
C
D
E
F
G
H
I
J
May 1993
June 1993
November 1993
January 1994
August 1994
June 1995
May 1996
October 1998
August 2000
The Model 3310A Aerodynamic Particle Sizer®Spectrometer
instruction manual (P/N 1933766) was originally released as a
Model APS33B Aerodynamic Particle Sizer instruction manual (P/N
1933310) in October 1987. Revisions were made throughout the
manual to reflect the new model number change.
In revision A, ampere ratings (Figure 3-2 and Table M-1) were
included.
In revision B, a change was made in the type of vacuum pump used
to draw aerosol through the system (see Figures G-24 and G-25).
In revision C, a change was made in the dimensions in Table M-1 in
Appendix M.
In revision D, changes were made to the APS System components
which now include the APS Advanced Software and the Model 3310
Inner Nozzle Insert Tool. Appendixes F and N were removed and all
subsequent appendixes renumbered.
In revision E, TSI’s customer service number was changed.
In revision F, minor text changes were made in Chapter 2.
In revision G, schematic 9060171 in Appendix M was revised.
In revision H, TSI’s “Limitation of Warranty and Liability” on page iii
was updated.
In revision I, the manual was reformatted to current style and
photographs were scanned in. TSI’s area code was changed from
612 to 651.
In revision J, TSI’s Limitation of Warranty and Liability was
updated.

iii
Part Number 1933766 / Revision J / August 2000
Copyright ©TSI Incorporated / November 1992–2000 / All rights reserved.
Address TSI Incorporated / 500 Cardigan Road / P.O. Box 64394 / St. Paul, MN 55164 /
USA
Fax No. [phone]
E-mail Address [email protected]
Limitation of Warranty
and Liability
(effective July 2000)
Seller warrants the goods sold hereunder, under normal use and service as
described in the operator's manual, shall be free from defects in workmanship and
material for (12) months, or the length of time specified in the operator's manual,
from the date of shipment to the customer. This warranty period is inclusive of any
statutory warranty. This limited warranty is subject to the following exclusions:
a. Hot-wire or hot-film sensors used with research anemometers, and certain other
components when indicated in specifications, are warranted for 90 days from
the date of shipment.
b. Parts repaired or replaced as a result of repair services are warranted to be free
from defects in workmanship and material, under normal use, for 90 days from
the date of shipment.
c. Seller does not provide any warranty on finished goods manufactured by others
or on any fuses, batteries or other consumable materials. Only the original
manufacturer's warranty applies.
d. Unless specifically authorized in a separate writing by Seller, Seller makes no
warranty with respect to, and shall have no liability in connection with, goods
which are incorporated into other products or equipment, or which are modified
by any person other than Seller.
The foregoing is IN LIEU OF all other warranties and is subject to the LIMITATIONS
stated herein. NO OTHER EXPRESS OR IMPLIED WARRANTY OF FITNESS FOR
PARTICULAR PURPOSE OR MERCHANTABILITY IS MADE.
TO THE EXTENT PERMITTED BY LAW, THE EXCLUSIVE REMEDY OF THE USER
OR BUYER, AND THE LIMIT OF SELLER'S LIABILITY FOR ANY AND ALL LOSSES,
INJURIES, OR DAMAGES CONCERNING THE GOODS (INCLUDING CLAIMS BASED
ON CONTRACT, NEGLIGENCE, TORT, STRICT LIABILITY OR OTHERWISE) SHALL
BE THE RETURN OF GOODS TO SELLER AND THE REFUND OF THE PURCHASE
PRICE, OR, AT THE OPTION OF SELLER, THE REPAIR OR REPLACEMENT OF THE
GOODS. IN NO EVENT SHALL SELLER BE LIABLE FOR ANY SPECIAL,
CONSEQUENTIAL OR INCIDENTAL DAMAGES. SELLER SHALL NOT BE
RESPONSIBLE FOR INSTALLATION, DISMANTLING OR REINSTALLATION COSTS
OR CHARGES. No Action, regardless of form, may be brought against Seller more
than 12 months after a cause of action has accrued. The goods returned under
warranty to Seller's factory shall be at Buyer's risk of loss, and will be returned, if at
all, at Seller's risk of loss.
Buyer and all users are deemed to have accepted this LIMITATION OF WARRANTY
AND LIABILITY, which contains the complete and exclusive limited warranty of
Seller. This LIMITATION OF WARRANTY AND LIABILITY may not be amended,
modified or its terms waived, except by writing signed by an Officer of Seller.
Service Policy Knowing that inoperative or defective instruments are as detrimental to TSI as they
are to our customers, our service policy is designed to give prompt attention to any
problems. If any malfunction is discovered, please contact your nearest sales office
or representative, or call TSI’s Particle Instrument Division at 1-800-874-3893 (USA)
or [phone].

iv Model 3310A Aerodynamic Particle Sizer®Spectrometer

Contents
v
Manual History............................................................................ii
Warranty.....................................................................................iii
Safety .......................................................................................xiii
About This Manual....................................................................xv
Purpose................................................................................. xv
Getting Help.......................................................................... xv
Reusing and Recycling .......................................................... xv
Submitting Comments .........................................................xvi
Chapters
1 Introduction....................................................................... 1-1
Overview ............................................................................. 1-1
System History.................................................................... 1-4
2 Installing the Sensor ......................................................... 2-1
Unpacking .......................................................................... 2-1
Selecting the Line Voltage.................................................... 2-2
Checking and Setting the Line Voltage ................................ 2-2
Checking and Changing Fuses............................................ 2-4
Replacing Faulty Fuses .................................................... 2-4
Changing Between European and American-Style Fuses.. 2-4
Attaching the Outer Inlet Tube............................................ 2-6
3 Description of the Sensor.................................................. 3-1
Front-Panel Switches and Indicators................................... 3-1
Flow System........................................................................ 3-3
Optics System..................................................................... 3-5
Signal Processing................................................................ 3-6
PMT Module..................................................................... 3-6
Timer Board..................................................................... 3-7
CPU Board ....................................................................... 3-8
4 Operating the APS ............................................................. 4-1
Starting up the Sensor........................................................ 4-1
Setting the Flows................................................................. 4-1
Checking the Inlet Pressure ................................................ 4-3
Checking the PMT Level ...................................................... 4-3
5 Particle Coincidence and Count Variance ........................ 5-1
Particle Coincidence............................................................ 5-1
Particle Count Variance....................................................... 5-2

vi Model 3310A Aerodynamic Particle Sizer®Spectrometer
6 Maintaining and Servicing the APS .................................. 6-1
Changing the Filters............................................................ 6-1
Cleaning the Nozzles ........................................................... 6-3
Inner Nozzle ..................................................................... 6-3
Outer Nozzle..................................................................... 6-5
7 Troubleshooting the Sensor.............................................. 7-1
8 Installing the Microcomputer System.............................. 8-1
Unpacking .......................................................................... 8-1
Selecting the Line Voltage ................................................... 8-1
Setting up the Microcomputer System................................. 8-1
Using the APS Software....................................................... 8-2
9 Basic Software Reference Guide ....................................... 9-1
Microcomputer System........................................................ 9-1
Software Programs and Text Files........................................ 9-1
Baud Rate........................................................................... 9-2
10 Operating Basic Software ................................................ 10-1
For Owners of the Data Analysis Center............................ 10-1
For Owners With Their Own Computer........................... 10-1
Loading the Software Onto a Hard Disk............................. 10-1
Software Function Keys..................................................... 10-2
Running the APS Basic Program ....................................... 10-3
Option 1 – Auto Run....................................................... 10-4
Option 2 – Clear Accumulator ........................................ 10-5
Option 3 – Manual Run.................................................. 10-6
Option 4 – Run Parameters ............................................ 10-7
Option 1 – Sample Time............................................... 10-7
Option 2 – Number of Samples .................................... 10-8
Option 3 – Particle Density .......................................... 10-8
Option 4 – Dilution Ratio............................................. 10-9
Option 5 – Efficiency Correct ......................................10-10
Options 6 Through F – the Auto Run Parameters........10-12
Option G – Respirable Mass........................................10-12
Option H – Disk Save..................................................10-13
Option I – Printout Heading........................................10-16
Option 5 – Size Distribution Graphs..............................10-17
Option 6 – Size Distribution Tables ...............................10-18
Option 7 – Accumulator Graphs....................................10-19
Option 8 – Accumulator Table .......................................10-20
Option 9 – Buffer Save...................................................10-21
Option 0 – Disk Options................................................10-21
Option 1.....................................................................10-22
Option 2.....................................................................10-23

Contents vii
Disk Errors.................................................................10-23
Option 3.....................................................................10-24
Option 4.....................................................................10-24
Option A – Select Printer ...............................................10-25
Option B – Test Calibration ...........................................10-25
Option C – End..............................................................10-25
Running the CREATE Program.........................................10-25
How the Program Works................................................10-26
Running the APSTEST Program........................................10-28
How the Program Works................................................10-29
11 Calibrating the APS System ............................................ 11-1
Taking Calibration Data.................................................... 11-1
APS Optics Subassembly................................................ 11-1
Preloaded Turntable....................................................... 11-5
Step-by-Step Procedure.................................................. 11-6
Running the NEWCAL Program......................................... 11-7
Option 1 – Make New Calib. File..................................... 11-9
Option 2 – Change Existing Calib. File............................ 11-9
Option 1 – Change Data .............................................11-12
Option 2 – Save Data in APS 3310A............................11-12
Option 3 – End...........................................................11-12
Using the Test Calibration Function.................................11-13
Atmospheric Pressure Correction for the APS...................11-17
Appendixes
A PMT Adjustments .............................................................. A-1
B Calculating the Respirable Mass.......................................B-1
C Calculations in NEWCAL ...................................................C-1
D Effects of Coincidence ......................................................D-1
Coincidence With 2-ns-Timer ..............................................D-1
Coincidence with the 66.67-ns Timer ..................................D-5
E Efficiency Data Files for the Model 3302 Diluter ............E-1
F Inverting the Optical Subassembly................................... F-1
Step 1 .............................................................................. F-2
Step 2 .............................................................................. F-3
Step 3 .............................................................................. F-4
Step 4 .............................................................................. F-6

viii Model 3310A Aerodynamic Particle Sizer®Spectrometer
Step 5 .............................................................................. F-8
Step 6 .............................................................................. F-9
Step 7 ............................................................................ F-11
Step 8 ............................................................................ F-12
Step 9 ............................................................................ F-13
Step 10 .......................................................................... F-14
Step 11 .......................................................................... F-16
Step 12 .......................................................................... F-16
Step 13 .......................................................................... F-17
Step 14 .......................................................................... F-18
Step 15 .......................................................................... F-19
G Powder Sizing With the Aerodynamic Particle Sizer .......G-1
Technique for Sizing ‘Difficult’ Powders ...............................G-1
H Typical Examples of Pulse-Pairs Output From the
Photomultiplier.................................................................H-1
I Bibliography of Scientific Papers Directly Related to
APS Sensor Performance.................................................... I-1
J Generating a Program Listing ........................................... J-1
K Technical Paper.................................................................K-1
L Model 3310A Sepcifications.............................................. L-1
M Electrical Schematics...................................................... M-1
Figures
1 Advisory Labels..................................................................xiii
1-1 TSI Model 3310A Aerodynamic Particle Sizer®
Spectrometer—APS on the Left with the Data Analysis
Center on the Right ....................................................... 1-1
1-2 Schematic of the Sensor’s Accelerating Orifice and the
Laser Velocimeter.......................................................... 1-3
2-1 Power Entry, Fuse and Voltage Module............................. 2-3
2-2 Orientation of the Voltage Selector Card ........................... 2-3
2-3 North American–Fusing Arrangement............................... 2-5
2-4 European–Fusing Arrangement ........................................ 2-5
2-5 Fuse Block/Cover Assembly ............................................. 2-6
2-6 Installing the Outer Inlet Tube.......................................... 2-7

Contents ix
3-1 Front Panel of the APS 3310A; the Callouts are
Explained in Table 3-1................................................... 3-1
3-2 Back Panel of the APS 3310A; the Callouts are
Explained in Table 3-2................................................... 3-2
3-3 APS Flow Diagram............................................................ 3-4
3-4 Schematic of the APS Optics............................................. 3-5
3-5 Optical Assembly, External View....................................... 3-6
5-1 Relationship Among Sampling Time, Particle
Concentration and Count Variance................................ 5-3
6-1 Bottom View of Optics Baseplate ...................................... 6-1
6-2 Components of the APS Flowmeter ................................... 6-2
6-3 Nozzle Assembly ............................................................... 6-4
9-1 Location of the DIP Switch on the CPU Board................... 9-3
11-1 The APS With an Inverted Optics Subassembly; Shown
Configured with the Model 3433 Small-Scale Powder
Disperser for Large-Size PSL Calibration...................... 11-2
11-2 Alternate APS Inlet Attached to the Nozzle Block:
aAlternate APS Inlet ................................................... 11-3
11-3 The Aerosol Outlet Tube Removed from the Disperser..... 11-3
11-4 Mating the APS Inlet (Top Cover Removed from APS) With
the Upper Nozzle of the Disperser: aAPS Inlet Nozzle;
bDisperser Mating Ring .............................................. 11-4
11-5 Final Configuration for an APS with a Noninverted
Optics Subassembly, and a Disperser for Large-Size
PSL Calibration ........................................................... 11-5
11-6 Printout of the Screen Data That Appears When
Calibrated Data is Transferred From the Computer
to the Sensor..............................................................11-14
11-7 Sample: 'Good’ Calibration Using the Test Calibration
Function.....................................................................11-15
11-8 Sample: ‘Poor’ Calibration Using the Test Calibration
Function.....................................................................11-16
11-9 Channel Shift With Atmospheric Pressure Change for
Mass Flowmeters........................................................11-17
11-10 LPP Channel Shift With Atmospheric Pressure
Change.......................................................................11-18
A-1 PMT Module With Regular Optics Installed....................... A-1
A-2 Location of the Slots for Adjusting the Two PMT
Potentiometers .............................................................. A-2
D-1 Conditions for Coincidence in the APS Sensor..................D-2

x Model 3310A Aerodynamic Particle Sizer®Spectrometer
D-2 Effects of Single Particles on Mass Distribution (0.5- to
15-Micrometer Program Version) ...................................D-4
F-1 The APS 3310A With Noninverted Optics: aInlet Nozzle;
bTop Cover; cSide Arm; dBottom Cover....................... F-2
F-2 The APS With Inlet, Covers and Sidearm Removed............ F-3
F-3 View of Movement Restrictor From Top of APS:
aMovement Restriction................................................. F-4
F-4 View of APS on its Side With Electrical Connections:
aMounting Block; bRear Upright Support Rod; cOutput
Signal Cable; dAnalog Out Coaxial; eLaser Power
Supply; fPhotomultiplier Power Supply......................... F-5
F-5 View of APS With Electrical Cables Disconnected; aPMT
Power Cable; bAnalog Out Cable; cSignal Cable to
CPU Board; dLaser Power Cable................................... F-6
F-6 APS Bottom View Showing Flowmeter Connections: a
Flowmeter Cables, Red Spot and Blue Spot; bSheath-Air
Control Valve Tubes; cTotal-Flow Flowmeter Outlet
Tube.............................................................................. F-7
F-7 APS View Showing Electrical Cable and Flow Tubing
Disconnected; aTotal Flow Flowmeter; bSheath-Air
Flowmeter ..................................................................... F-7
F-8 View of APS Showing Free Optics Block............................ F-8
F-9 Optics Block Removed From APS Frame: aLaser Power-
Supply Socket ............................................................... F-9
F-10 Control PC Board Mounting Screw: aScrew ................... F-10
F-11 Removing the Control PC Board...................................... F-10
F-12 Front, Left-Hand Side of APS Showing Old and New
Mounting Block Screw Holes: Front Left-Hand Mounting-
Block Screws: aOld Location; bNew Location............. F-11
F-13 Rear Mounting Block’s Screw Holes: Rear Left-Hand
Mounting-Block Screws: aOld Location; bNew
Location ...................................................................... F-12
F-14 Inverting the Outer Frame Mounting Blocks: aLaser
Power Supply Socket; bCounter Sunk Screws............. F-13
F-15 Orienting Electrical Cables and Flow Tubing:
aTotal-Flow Flowmeter Tube; bAnalog Out Coaxial
Cable; cPhotomultiplier Power Supply Cable; dOutput
Signal Cable................................................................ F-14
F-16 Reinserting the Inverted Optics Block............................. F-15
F-17 The Inverted Optics Block In Place.................................. F-15
F-18 All Mounting Blocks in Place .......................................... F-16

Contents xi
F-19 Reconnected Flowmeter and PMT Cable and Tubing:
aFlowmeter Cables, Red Spot and Blue Spot; bSheath-
Air Flowmeter Tube; cPhotomultiplier Power-
Supply Cable; dAnalog Out Coaxial Cable; eSignal
Output Cable............................................................... F-17
F-20 Sheath-Air Tubing Connection: aSheath-Air Flowmeter
Tube............................................................................ F-18
F-21 Final Tubing Connections and Side-Arm Fastened:
aSide Arm; bBranch Tee; cTube (P/N 1030797)........ F-18
F-22 Bottom View of Covers and Nozzle Replaced: aAlternate
APS Inlet Nozzle; bSpacer Ring ................................... F-19
F-23 Optics Inversion is Now Complete!.................................. F-20
F-24 Plumbing of the Conventional Optical Subassembly........ F-21
F-25 Plumbing of the Inverted Optical Subassembly............... F-22
G-1 Number and Mass Distributions With the PMT Level
at 300 Millivolts.............................................................G-2
G-2 The Same Aerosol as Shown in Figure G-1; PMT Level
Adjusted to 100 Millivolts ..............................................G-4
G-3 The Same Aerosol as Shown in Figure G-2; PMT Level
Adjusted to 50 Millivolts................................................G-5
H-1 Analog Output of the APS Sensor for 0.546-Micrometer-
Diameter PSL Spheres...................................................H-1
H-2 Analog Output of the APS Sensor for 10-Micrometer-
Diameter PSL Spheres...................................................H-2
H-3 Analog Output of the APS Sensor for PSL Particles at
29 Micrometers in Diameter ..........................................H-3
H-4 Analog Output of the APS Sensor for PSL Spheres at
Diameters of 0.79 and 1.091 Micrometers .....................H-4
Tables
2-1 Components of the APS System........................................ 2-1
2-2 Matching the Fuse to the Line Voltage .............................. 2-4
3-1 Front Panel Callouts......................................................... 3-2
3-2 Back Panel Callouts.......................................................... 3-3
5-1 Concentration Levels (Particles/cm3) for 1-, 5-, and 10-
Percent Coincidence Error for Selected Particle
Diameters...................................................................... 5-2
7-1 Troubleshooting Symptoms and Recommendations .......... 7-1

xii Model 3310A Aerodynamic Particle Sizer®Spectrometer
8-1 Data Analysis Center Components.................................... 8-1
8-2 Pin Connections for the Model 3310A ............................... 8-2
9-1 Software Programs and Text Files..................................... 9-1
9-2 Baud Rates on the CPU Board.......................................... 9-4
10-1 APS Software Keys and Their Functions.......................... 10-3
10-2 Format for Storing Data Files in Sequence.....................10-14
10-3 Sample Printout from the CREATE Program ..................10-28
11-1 Example of a Calibration Session for the 0.5- to
30-Micrometer Version of the Sensor Program............. 11-8
11-2 Sample of Calibration Data Points for the 0.5- to
15-Micrometer Version of the Sensor Program............11-11
B-1 ACGIH Definition of Respirable Mass................................B-1
B-2 Respirable Mass Fractions Used in the APS Software
Calculations ..................................................................B-2
D-1 Concentration Levels (Particles/Cm3) for 1, 5, and
10 Percent Coincidence Error for 3 Particle Diameters...D-3
D-2 Concentration Levels (Particles/Cm3) for 1, 5, and
10 Percent Coincidence Error for Four Particle
Diameters......................................................................D-5
E-1 Filename: D20.................................................................E-1
E-2 Filename: D100...............................................................E-2
E-3 Filename: D400...............................................................E-3
E-4 Filename: D2000.............................................................E-4
E-5 Filename: D10000...........................................................E-5
L-1 Specifications of the Model 3310A..................................... L-1

Safety
xiii
WARNING
The use of controls, adjustments, or procedures other than those specified in this
manual may result in exposure to hazardous radiation exposure.
The sensor is a laser-based instrument. As such, certain
precautions must be taken when using and servicing it. In
particular, do not remove any parts unless specified in this
instruction manual or you may expose yourself to hazardous
optical radiation.
Four advisory labels have been attached to the APS components for
your benefit. Reproductions of these labels and the label locations
are given below.
a.
500 CARDIGAN ROAD
ST. PAUL, MINNESOTA
MADE IN U.S.A. 55126
MODEL
SERIAL
DATE
TSI®
b.
DANGER
LASER RADIATION WHEN
OPEN. AVOID DIRECT
EXPOSURE TO BEAM
c.
CLASS 1 LASER PRODUCT
THIS PRODUCT IS IN
COMPLETE COMPLIANCE WITH
21 CFR 1040.10 AND 1040.11.
Figure 1
Advisory Labels: (a) identification label (on the back panel); (b) warning label (on
the optics housing); (c) product compliance label

xiv Model 3310A Aerodynamic Particle Sizer®Spectrometer

About This Manual
xv
Purpose
The Model 3310A Instruction Manual describes how to use the
revised version of TSI’s Aerodynamic Particle Sizer®Spectrometer
(APS).
Getting Help
To obtain assistance with this product, or simply to submit
suggestions, please contact Customer Service:
TSI Incorporated
Particle Instrument Division
P.O. Box 64394
St. Paul, MN 55164 USA
Fax: [phone]
Telephone: [phone] (USA) or [phone]
E-mail Address: [email protected]
Reusing and Recycling
As part of TSI Incorporated’s effort to have a minimal negative
impact on the communities in which its products are manufactured
and used:
!This manual uses recycled paper.
!Shrink-wrapping, which is difficult to recycle, has been reduced
to the manual’s outer binder.
!This manual has been shipped, along with the instrument, in a
reusable carton.

xvi Model 3310A Aerodynamic Particle Sizer®Spectrometer
Submitting Comments
TSI values your comments and suggestions on this manual. Please
use the comment sheet, on the last page of this manual, to send us
your opinion on the manual’s usability, to suggest specific
improvements, or to report any technical errors.
If the comment sheet has already been used, mail, fax or e-mail
your comments on another sheet of paper to:
TSI Incorporated
Particle Instrument Division
P.O. Box 64394
St. Paul, MN 55164
Fax: [phone]
E-mail address: [email protected]

CHAPTER 1
Introduction
1-1
If you purchased a Model 3310A Aerodynamic Particle Sizer®
Spectrometer system, you received the APS Advanced Software.
However, this manual only covers the operation of the Model 3310A
sensor with the BASIC software. Use the separate APS Advanced
Software manual as a reference for that software package.
Overview
The Model 3310A APS System consists of two components (see
Figure 1-1):
!The Model 3310A Aerodynamic Particle Sizer®Spectrometer
(APS)
!A Data Analysis Center
The Data Analysis Center consists of an IBM or IBM-compatible
computer with a math coprocessor, a VGA color monitor and a dot-
matrix printer.
Figure 1-1
TSI Model 3310A Aerodynamic Particle Sizer®Spectrometer—APS on the Left with
the Data Analysis Center on the Right

1-2 Model 3310A Aerodynamic Particle Sizer®Spectrometer
In real time, the sensor measures particle aerodynamic diameter,
that is, the diameter of a unit density sphere with the same settling
velocity as the particle in question.
Within the sensor, the particle-laden air passes through a thin-
walled orifice (inner nozzle). As particles leave the inner nozzle, they
are accelerated by clean sheath air and exit an outer nozzle in an
accelerating flow field. Due to higher inertia, large particles lag
behind the air. Since velocity lag is uniquely related to the
aerodynamic diameter of a particle, the aerodynamic diameter of a
particle can be measured by measuring the velocity of a particle as
it exits the orifice (outer nozzle).
To measure the particle velocity, a laser beam is first split and
focused into two rectangular beams in front of the orifice. The light
scattered by a particle is focused through a series of lenses onto a
photomultiplier tube. The tube emits two pulses separated by the
time it takes the particle to cross the distance between the two
beams. This electronically measured time interval is then used to
calculate the aerodynamic diameter of the particle.
The two main parts of the sensor are the accelerating orifice and
the laser velocimeter (Figure 1-2).
The accelerating orifice consists of an outer orifice, measuring
1.0 millimeter in diameter, and an inner nozzle, measuring
0.8 millimeter in diameter. While 20 percent of the sampled aerosol
passes through the inner nozzle, the remaining 80 percent passes
through a filter and flowmeter and is reintroduced as sheath air,
confining the aerosol particles to the central region of the jet where
the air velocity is uniform.
An air velocity of approximately 150 meters per second is
maintained at the orifice by keeping the sensing chamber at a
pressure of 125 centimeters of water below the ambient inlet pres-
sure. A pressure transducer controls a feedback loop which in turn
controls the vacuum pump, and thus maintains this constant
pressure drop.

Introduction 1-3
The laser velocimeter uses a 2-milliwatt, polarized helium-neon
(HeNe) laser as its light source. In its path to the photomultiplier
tube, the laser beam first passes through a beam expander and is
then focused by a positive lens. A calcite plate follows the positive
lens, splitting the beam via polarization. Finally, a cylindrical lens
forms the two rectangular cross-section beams. The two split beams
are blocked by a beam stop; the forward scattered light is collected
and focused onto the photomultiplier tube.
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Photomultiplier
Tube
Pressure
Transducer
Scattered Light
Laser
Velocimeter
Filter
Flowmeter
Focusing
Optics
Accelerating
Orifice Nozzle
Laser
Inner Nozzle/Sensor Flow
1 Liter Per Minute Outer Nozzle/Sheath Flow
4 Liters Per Minute
Total Flow
5 Liters Per Minute
Filter Flowmeter
Sheath Air Valve
4 Liters Per Minute
Internal
Vacuum Pump
Aerosol In
Figure 1-2
Schematic of the Sensor’s Accelerating Orifice and the Laser Velocimeter

1-4 Model 3310A Aerodynamic Particle Sizer®Spectrometer
The two pulses generated by the photomultiplier tube cause two
digital pulses to be generated by a triggering circuit. Two high-
speed digital clocks, one with 2-nanosecond resolution, the other
with 66.67-nanosecond resolution, measure the time between the
two pulses. The measured time intervals are then transferred to a
multichannel accumulator incorporated into the circuitry of the
APS System. The microcomputer system is then used for data
analysis and data display.
System History
The Model 3310 Aerodynamic Particle Sizer®Spectrometer (APS)
was introduced in January 1987 to replace the Model 3300. The
Model 3310A Aerodynamic Particle Sizer (APS) was introduced in
November 1992 to replace the Model 3310. As explained below, the
revision incorporates several hardware changes, new software in
the BASIC computer programming language and the Advanced
Software package in the “C” programming language.
There are four major hardware changes in the Model 3310A:
!The accumulator board, which is now referred to as the Central
Processor Unit (CPU) board, has been completely redesigned. It
incorporates a Large Particle Processor (LPP) to validate large
particle counts. The board also allows for serial data transfer to
the controlling IBM Personal Computer®XT/AT/PS 2 and stores
calibration data. The advanced LPP circuitry extends the upper
size range from 15 to 30 micrometers.
!A modified internal support framework allows inversion of the
optical subassembly. The sensor aerosol inlet can, therefore, be
mounted either on the top or bottom of the instrument.
Mounting the inlet on the lower position accommodates powder
sizing with the Model 3433 Small-Scale Powder Disperser.
!The optics plate and center plate have both been modified.
!A magnetic shield around the photomultiplier tube has been
added. The shield limits the sensitivity of the sensor to its
orientation in the earth’s magnetic field.