2B Technologies 405 nm User manual

Model 405 nm NO2/NO/NOxMonitor Manual Rev. D
i
NO2/NO/NOxMonitor
2BTechnologies, Inc.
OPERATION MANUAL
Model 405 nm
© Copyright 2016, 2B Technologies, Inc.
All rights reserved.
Technical Support:
www.twobtech.com/techsupport
[e-mail]
[phone]

Model 405 nm NO2/NO/NOxMonitor Manual Rev. D
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Contents
IDENTIFICATION RECORDS iv
PRINTING HISTORY v
WARRANTY STATEMENT vi
WARNINGS viii
1. NO2/NO/NOXMONITOR INTRODUCTION 1
1.1. Theory of Operation................................................................................................................. 2
1.2. Adaptive Filter.......................................................................................................................... 4
2. NO2/NO/NOXMONITOR SPECIFICATIONS 5
3. OPERATION 6
3.1. Shipping Box Contents............................................................................................................ 6
3.2. Pre-Operation Flow Settings of the Monitor............................................................................ 6
3.3. Operation of the Monitor.......................................................................................................... 7
3.4. Connections and Setup ........................................................................................................... 7
3.5. Measurement of the Zero Offset; Auto Zero Function............................................................. 8
3.6. Collecting Data from the Analog Output.................................................................................. 8
3.7. Collecting Data over the Serial Port in Real Time................................................................... 8
3.8. Data Averaging and Data Logging ........................................................................................10
3.9. Summary of Operating Recommendations ...........................................................................10
4. THE MENU 11
4.1. Menu Tree .............................................................................................................................12
4.2. To Start Logging Data ...........................................................................................................13
4.3. To Stop Logging Data............................................................................................................ 14
4.4. To Transmit Logged Data......................................................................................................15
4.5. To Average Data....................................................................................................................15
4.6. Instrument Configuration .......................................................................................................16
4.7. To Set the Time and Date .....................................................................................................16
4.8 Calibration Parameters - Overview........................................................................................16
4.9. To Set the NO2and NO Calibration Parameters................................................................... 17
4.10. To Set the Flow Meter Slopes............................................................................................... 18
4.11. To Change the Output Baud Rate.........................................................................................18
4.12. To Change the Analog Output Scaling Factor....................................................................... 19
4.13.To Read the Number of Hours of Monitor Use...................................................................... 19
4.14. Measurement Units ...............................................................................................................19
4.14.1.. To Change the Units for Internal Cell Temperature and Pressure ..........................19
4.14.2.. To Change the Units for NO2and NO...................................................................... 20
4.15. To Test the LED Voltage and Precision ................................................................................20
4.16. Measurement Modes............................................................................................................. 20
4.16.1.. NO2Mode................................................................................................................. 21
4.16.2.. NO2and NO Mode ................................................................................................... 21
4.16.3.. NO Mode..................................................................................................................21
4.17. Auto Zeroing.......................................................................................................................... 21
4.17.1.. Zero Duration ........................................................................................................... 21
4.17.2.. Zero Frequency........................................................................................................21
5. REMOTE CONTROL VIA SERIAL CONNECTION 22

Model 405 nm NO2/NO/NOxMonitor Manual Rev. D
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6. MAINTENANCE 24
7. CALIBRATION 25
7.1. Introduction............................................................................................................................ 25
7.1.1.... Equipment Required................................................................................................. 25
7.1.2.... Setup Check............................................................................................................. 26
7.2. Calibration Procedure............................................................................................................26
7.2.1.... Instrument Preparation.............................................................................................26
7.2.2.... Measurement of Zero Air.......................................................................................... 27
7.2.3.... Measurement of NO2and NO Standards.................................................................27
7.2.4.... Calibration Curve...................................................................................................... 27
8. PERIODIC ZERO AND SPAN CHECKS 28
9. TROUBLESHOOTING 29
10. INSTRUMENT LAYOUT 32
11. WIRING CONNECTIONS 38
12. SPARE PARTS 39
13. SERVICE LOG 40
Appendix A: Using the 2B Technologies Display and Graphing Software 42

Model 405 nm NO2/NO/NOxMonitor Manual Rev. D
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IDENTIFICATION RECORDS
Record the following information for future reference:
Unit serial number: ______________________________________
Warranty start date: _______________________________________
(date of receipt)

Model 405 nm NO2/NO/NOxMonitor Manual Rev. D
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PRINTING HISTORY
This manual covers the Model 405 nm NO2/NO/NOxMonitor™used for measurement
of atmospheric nitrogen dioxide (NO2), nitric oxide (NO) and NOx(NO + NO2) over a
dynamic range extending from a few parts per billion by volume (referred to herein as
simply ppb) up to 10 parts-per-million by volume (ppm) for NO2and 2 ppm for NO.
New editions of this manual are complete revisions that reflect updates to the
instrument itself, as well as clarifications, additions and other modifications of the text.
Revision A ............................................................................................December 2013
Revision B ..............................................................................................February 2014
Revision C.......................................................................................................May 2015
Revision D, serial number 1021 and above ...................................................June 2016
TRADEMARKS & PATENTS
2B Technologies™, 2B Tech™, 2B™, NO2/NO/NOxMonitor™ and Model 405
nm™are trademarks of 2B Technologies, Inc.
CONFIDENTIALITY
The information contained in this manual may be confidential and proprietary, and is the
property of 2B Technologies, Inc. Information disclosed herein shall not be used to
manufacture, construct, or otherwise reproduce the goods disclosed herein. The
information disclosed herein shall not be disclosed to others or made public in any
manner without the expressed written consent of 2B Technologies, Inc.
© Copyright 2001-2016, 2B Technologies, Inc.
All rights reserved.

Model 405 nm NO2/NO/NOxMonitor Manual Rev. D
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WARRANTY STATEMENT
2B Technologies, Inc. warrants its products against defects in materials and
workmanship. 2B Technologies will, at its option, repair or replace products that prove
to be defective. The warranty set forth is exclusive and no other warranty, whether
written or oral, is expressed or implied. 2B Technologies specifically disclaims the
implied warranties of merchantability and fitness for a particular purpose.
Warranty Period
The warranty period is one (1) year from date of receipt by the purchaser, but in no event
more than thirteen (13) months from original invoice date from 2B Technologies, Inc.
Warranty Service
Warranty Service is provided to customers via web ticket, email and phone support,
Monday - Friday, from 9:00 a.m. to 5:00 p.m., Mountain Time USA. The preferred
method of contacting us is through our web ticketing software at:
www.twobtech.com/techsupport
This way all technical staff at 2B Tech will be alerted of your problem and be able to
respond. When you receive an email reply, please click on the Ticket link provided to
continue to communicate with us directly over the internet. The web ticket approach
to customer service allows us to better track your problem and be certain that you get
a timely response. We at 2B Tech pride ourselves on the excellent customer service
we provide.
You may also contact us by email at te[email protected] or by phone at
[phone]. In either case, a web ticket will be created, and future
communications with you will be through though that ticket.
Initial support involves trouble-shooting and determination of parts to be shipped from
2B Technologies to the customer in order to return the product to operation within
stated specifications. If such support is not efficient and effective, the product may be
returned to 2B Technologies for repair or replacement. Prior to returning the product,
a Repair Authorization Number (RA) must be obtained from the 2B Technologies
Service Department. We will provide you with a simple Repair Authorization Form to
fill out to return with the instrument.
Shipping
2B Technologies will pay freight charges for replacement or repaired products shipped
to the customer site. Customers shall pay freight charges for all products returning to
2B Technologies.

Model 405 nm NO2/NO/NOxMonitor Manual Rev. D
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Conditions
The foregoing warranty shall not apply to defects resulting from improper or
inadequate maintenance, adjustment, calibration or operation by the customer.
Maintenance, adjustment, calibration or operation must be performed in accordance
with instructions stated in this manual. Use of maintenance materials purchased from
suppliers other than 2B Technologies will void this warranty.
Limitation of Remedies and Liability
The remedies provided herein are the customer's sole and exclusive remedies. In no
event shall 2B Technologies be liable for direct, indirect, special, incidental or
consequential damages (including loss of profits) whether based on contract, tort or
any other legal theory. This manual is believed to be accurate at the time of
publication and no responsibility is taken for any errors that may be present. In no
event shall 2B Technologies be liable for incidental or consequential damages in
connection with or arising from the use of this manual and its accompanying related
materials. Warranty is valid only for the country designated on the 2B Technologies
quote or invoice.
Safety Warning
The Model 405 nm NO2/NO/NOxMonitor is designed to use an internal generator of
ozone (O3) to oxidize NO to NO2. Ozone is a toxic gas and should be handled with
caution. Under normal operating conditions, the instrument will produce ~6 ppm O3in
air. The instrument is equipped with an internal ozone scrubber to remove ozone
before venting the sample. Although the scrubber is catalytic, it does have a limited
lifetime and should be replaced at least every 12 months. For this reason, it is
recommended to properly vent the output of the instrument to protect against any
unscrubbed O3. The outlet should not be vented near the inlet of any NOxor ozone
monitor inlets to avoid false measurements.
The NIOSH exposure limit for ozone is 0.1 ppm or 100 ppb (8-hour time-weighted
average).

Model 405 nm NO2/NO/NOxMonitor Manual Rev. D
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WARNINGS
ENGLISH
WARNING:
Any operation requiring access to the inside of the equipment, could result
in injury. To avoid potentially dangerous shock, disconnect from power
supply before opening the equipment.
WARNING:
This symbol, on the instrument indicates that the user should refer to
the manual for operating instructions.
WARNING:
If this instrument is used in a manner not specified by 2B Technologies,
Inc. USA, the protection provided by the instrument may be impaired.
ESPAÑOL
ATENCION:
Cualquier operación que requiera acceso al interior del equipo, puede
causar una lesión. Para evitar peligros potenciales, desconectarlo de la
alimentación a red antes de abrir el equipo.
ATENCION:
Este símbolo, en el instrumento indica que el usuario debería
referirse al manual para instrucciones de funcionamiento.
ATENCION:
Si este instrumento se usa de una forma no especificada por 2B
Technologies, Inc., USA, puede desactivarse la protección suministrada
por el instrumento.
FRANÇAIS
ATTENTION:
Chaque opération à l’intérieur de l’appareil, peut causer du préjudice. Afin
d’éviter un shock qui pourrait être dangereux, disconnectez l’appareil du
réseau avant de l’ouvrir.
ATTENTION:
Le symbol, indique que l’utilisateur doit consulter le manuel
d’instructions.
ATTENTION:
Si l’instrument n’est pas utilisé suivant les instructions de 2B Technologies,
Inc., USA, les dispositions de sécurité de l’appareil ne sont plus valables.
DEUTSCH
WARNHINWEIS:
Vor dem Öffnen des Gerätes Netzstecker ziehen!
WARNHINWEIS:
Dieses, auf dem Gerät weist darauf hin, dab der Anwender zuerst
das entsprechende Kapitel in der Bedienungsanleitung lesen sollte.
WARNHINWEIS:
Wenn das Gerät nicht wie durch die Firma 2B Technologies, Inc., USA,
vorgeschrieben und im Handbuch beschrieben betrieben wird, können
die im Gerät eingebauten Schutzvorrichtungen beeinträchtigt werden.
ITALIANO
ATTENZIONE:
Qualsiasi intervento debba essere effettuato sullo strumento può essere
potenzialmente pericoloso a causa della corrente elettrica.
Il cavo di alimentazione deve essere staccato dallo strumento prima della
sua apertura.
ATTENZIONE:
Il simbolo, sullo strumento avverte l’utilizzatore di consultare il
Manuale di Istruzioni alla sezione specifica.
ATTENZIONE:
Se questo strumento viene utilizzato in maniera non conforme alle
specifiche di 2B Technologies, Inc. USA, le protezioni di cui esso è dotato
potrebbero essere alterate.
DUTCH
OPGELET:
Iedere handeling binnenin het toestel kan beschadiging veroorzaken.
Om iedere mogelijk gevaarlijke shock te vermijden moet de aansluiting
met het net verbroken worden, vóór het openen van het toestel.
OPGELET:
Het symbool, geeft aan dat de gebruiker de instructies in de
handleiding moet raadplegen.
OPGELET:
Indien het toestel niet gebruikt wordt volgens de richtlijnen van 2B
Technologies, Inc., USA gelden de veiligheidsvoorzieningen niet meer.
CHINESE
警告：
任何需要接触设备内部的操作均可能造成人身伤害。为避免可能的触电危险，请
在打开设备前切断电源。
警告：
这个符号 在仪器上表示用户应参考说明书上的操作指南。
警告 :
如果仪器没有按照美国2B科技公司指定方式操作，仪器的保护性能会减弱。
JAPANESE
警告：
機器の内部で操作する時、怪我できます。危険な衝撃を回避
するために、機器を開ける前に、電源を切断してください。
警告：
機器でこの記号 を見れば、マニュアルを読んでください。
警告：
この機器は2B テクノロジー会社、
USAの指定でしなければ、機器の保護が損なえます。

Model 405 nm NO2/NO/NOxMonitor Manual Rev. D
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1. NO2/NO/NOX MONITOR INTRODUCTION
The 2B Technologies Model 405 nm NO2/NO/NOxMonitor™is designed to enable
accurate measurements of atmospheric nitrogen dioxide (NO2), nitric oxide (NO) and
NOx(NO + NO2) over a dynamic range extending from a few parts per billion by
volume (referred to herein as simply ppb) up to 10 parts-per-million by volume (ppm)
for NO2and 2 ppm for NO based on the absorption of visible light at 405 nanometers
(nm).
The Model 405 nm provides an absolute method for measuring NO2based on the
Beer-Lambert Law and thus requires only infrequent calibration. The NO2
measurement is analogous to the measurement of O3using a conventional
absorbance-based ozone monitor; the two main differences are the use of 405 nm
light for NO2in place of 254 nm light for O3, and a much longer path length of ~2
meters (vs. 15-30 cm for ozone) to compensate for the much lower absorption cross
section of NO2. The long path length is achieved by use of a cell with a tubular design
that provides low volume and rapid gas exchange.
Nitric oxide is measured by measuring the light intensities with and without ozone
added to oxidize NO to NO2. As described in more detail below, the result is a “semi-
direct” measurement of NO in that the NO concentration is output directly and not
based on subtraction of NO2concentration from a total NOxconcentration. Instead,
the NOxconcentration is computed as the sum of the measurements of NO2and NO.
The NO2/NO/NOxMonitor is provided with a NIST-traceable calibration. Because
detection is based on the absolute method of absorbance, frequent calibration of the
span (sensitivity) is not required.

Model 405 nm NO2/NO/NOxMonitor Manual Rev. D
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1.1. Theory of Operation
Figure 1.1 is a simplified schematic diagram of the Model 405 nm NO2/NO/NOx
Monitor.
Figure 1.1. Schematic Diagram of the Model 405 nm NO2/NO/NOxMonitor.
Sample air is continuously drawn through the instrument by the Pump at a flow rate of
~1.5 L/min. The NO2Scrubber Valve alternately bypasses and sends the sample air
through a heated NO2scrubber to remove all NO2in the sample. The NO2-scrubbed
or unscrubbed air passes through the Reactor Volume and the DewLineTM Nafion
Tubes (to equilibrate humidity), through the Optical Cell and through the Cell Flow
Meter. Alternate switching of the NO2Scrubber Valve once every 5 seconds allows
the measurement of a light intensity in the absence (Io) of NO2and presence (I) of
NO2. The Beer-Lambert Law is then used to calculate the concentration of NO2from I
and Io:
󰇟󰇠 
 
Here, Lis the path length (~2.1 m) and σis the absorption cross section (~6.06 × 10-19
cm2molec-1) for NO2averaged over the light-emitting diode (LED) emission centered
on 405 nm. The measurement provides an absolute NO2concentration in
molecules/cm3. In order to convert this concentration to a mixing ratio (fraction of total
air molecules that are NO2), we also measure the cell temperature and pressure,
which determines the total concentration of air molecules. From the temperature and
pressure we use the ideal gas law to calculate the concentration of air molecules, M,
in the optical cell. Nitrogen dioxide in units of ppb is then given by:

Model 405 nm NO2/NO/NOxMonitor Manual Rev. D
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󰇟󰇠  󰇟󰇠
󰇟󰇠   󰇡 󰇢
where NAis Avogadro’s number (6.02214129 x 1023 molec/mol), Ris the gas constant
(82.05746 cm3atm K−1 mol−1), Tis the absolute temperature in K, and Pis the cell
pressure in atmospheres.
Nitric oxide is measured by bypassing the NO2Scrubber and measuring the light
intensity while adding (I) or not adding (Io) ozone to convert NO to NO2according to
the well known reaction:
NO + O3→ NO2+ O2(1)
As in all our instruments, a DewLineTM Nafion®tube is used to equilibrate humidity
during Iand Iomeasurements, so that any water vapor interference due to refractive
effects on light transmission through the optical cell is eliminated.
NOxis obtained by adding the measurements of NO2and NO. The instrument may be
operated in continuous NO2or NO modes, or in a mode where NO2and NO are
alternately measured, once every 5 seconds.
As discussed above, the pressure and temperature within the absorption cell is
measured so that the NO2concentration can be expressed as a mixing ratio in parts-
per-billion by volume (ppb). The instrument displays and records the cell temperature
and pressure in addition to the NO2mixing ratio. The cell pressure is displayed and
logged in units of either torr or mbar, and the cell temperature in units of either °C or
K.
In principle, the measurement of NO2by absorbance at 405 nm requires no external
calibration; it is an absolute method. However, factors such as variability in the LED
peak emission wavelength and band width, and non-linearity of the photodiode and
amplifier response, can result in a small measurement error. Therefore, each
instrument is calibrated against NIST-traceable standards of NO and NO2. These
results are used to calibrate the Model 405 nm with respect to an offset and slope
(gain or sensitivity). The corrections for offset and slope are recorded in the
instrument Birth Certificate and on a calibration sticker that can be viewed by
removing the top cover of the instrument. These calibration parameters are entered
into the microprocessor memory prior to shipment. The user may change the slope
and offset calibration parameters from the front panel by entering the Menu if desired.
It is recommended that the instrument be recalibrated at least once annually and
preferably more frequently. The offset may drift on time scales of hours to days due to
temperature change or chemical contamination of the absorption cell. As described
below, an Auto Zero function is available to periodically adjust the baseline
measurement to zero using an internal zero scrubber.

Model 405 nm NO2/NO/NOxMonitor Manual Rev. D
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1.2. Adaptive Filter
The Model 405 nm firmware processes sample concentration data through a built-in
adaptive filter. During operation, the firmware may automatically switch between two
different filter lengths based on the conditions at hand. During the measurement of
stable concentrations, the firmware, by default, computes an average of the last 36
raw measurements, or 3 minutes of measurements. This provides smooth and stable
readings by averaging out a considerable amount of random noise to improve the
precision. If the filter detects rapid changes in concentration, the filter reduces the
averaging to only 4 samples or 20 seconds to allow the analyzer to respond more
quickly. Two conditions must be simultaneously met to switch to the short filter. First,
the instantaneous concentration must differ from the average in the long filter by at
least 40 ppb. Second, the instantaneous concentration must differ from the average in
the long filter by at least 10% of the average in the long filter. The lengths of the long
and short filter can be changed as well as the minimum difference and percent
difference. This can be done via the serial connection as outlined in the Serial Menu
section in this manual (Section 5).
To disable the adaptive filter, set the short filter length to 1, the difference to 0, and the
percent to 0.

Model 405 nm NO2/NO/NOxMonitor Manual Rev. D
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2. NO2/NO/NOX MONITOR SPECIFICATIONS
Principle of Measurement
Direct absorbance of NO2at 405 nm
Measurement Modes
NO2only; NO only; NO, NO2and NOx
Linear Dynamic Range
0-10 ppm for NO2; 0-2 ppm for NO
Resolution
0.1 ppb
Precision (1σ rms noise)
< 0.5 ppb or 0.5% of reading (with adaptive filter1)
Accuracy
Greater of 2 ppb or 2% of reading
Limit of Detection (2σ)
< 1 ppb (with adaptive filter1)
Flow Rate (nominal)
1.8 Liter/min
Flow Rate Requirement
1.4 Liter/min
Response Time, 100% of Step
Change
10 s for 5-s averaging
20 s with adaptive filter1
Measurement Frequency
0.2 Hz (once every 5 s)
Averaging Times
5 s, 1 min, 5 min, 1 hr
Internal Data Logger Capacity
8,192 lines (5 s avg. = 1.4 days; 1 min avg = 5.7 days;
5 min avg = 1.0 mo; 1 hr avg = 0.94 yr); increased capacity
with optional micro-SD Drive
Concentration Units
ppb, pphm, ppm
Pressure Units
mbar, torr
Temperature Units
°C, K
T and P Corrected
Yes
Operating Temperature Range
10 to 50 °C
Operating Altitude
~0-30 km (~30-1000 mbar)
Power Requirement;
Battery or 110/220 VAC Power Pack
11-14 V dc or 120/240 V ac, 1.3 A at 12 V, 16 watt
Max: 2.5 A at 12 V, 30 watt (warmup)
Size
Rackmount: 17" w x 14.5" d x 5.5" h (43 x 37 x 14 cm)
Weight
18.6 lb (8.4 kg)
Data Outputs
USB, RS232, 0-2.5 V Analog, Optional 4-20 mA Analog
Data Transfer Baud Rates
2400, 4800, 19200
Output Ranges
User-defined scaling factor in menu
DewLine™
Yes
Long Life Pump
Yes, 15,000 hr
Flow Meter
Yes
Options
Bluetooth for wireless data transmission;
4-20 mA analog output
1An adaptive filter may be selected from the menu, making signal averaging similar to competing NOx
monitors. Specifications above are for default parameters: Change Difference = 40 ppb, Change
Percent = 10%, Short Filter = 4 pts (20 s), Long Filter = 36 pts (3 min). Adaptive filter parameters may
be adjusted by the user.

Model 405 nm NO2/NO/NOxMonitor Manual Rev. D
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3. OPERATION
Please read all the following information before attempting to install the Model 405 nm
NO2/NO/NOxMonitor. For assistance, please call 2B Technologies at [phone].
NOTE:
Save the shipping carton and packing materials that came with the Monitor. If
the NO2/NO/NOxMonitor must be returned to the factory, pack it in the original
carton. Any repairs as a result of damage incurred during shipping will be
charged.
3.1. Shipping Box Contents
Open the shipping box and verify that it contains all of the items on the shipping list. If
anything is missing or obviously damaged, contact 2B Technologies immediately.
3.2. Pre-Operation Flow Settings of the Monitor
The Model 405 nm has two independent flows, which need to be verified and adjusted
before operating the instrument. The two volumetric flow rates measured and
independently adjusted are:
Cell Flow Rate (1400-1800 cm3/min): The cell flow rate of sample gas and ozone/air
through the reactor volume and optical cell.
Ozone Flow Rate (60-80 cm3/min): The flow rate of ozone/air mixed into the sample
flow stream.
These flow rates are adjusted to be in the ranges specified above at the factory.
However, due to changes in altitude and thus pressure, the two flow rates need to be
verified and adjusted to be within the specified ranges if necessary. To do this, follow
the flow rates on the LCD or serial output. The Cell Flow, displayed as CF, should be
in the range 1400-1800 cm3/min. This flow can be adjusted by the needle valve
located on the back panel labeled “Cell Flow”. The Ozone Flow, displayed as O3F,
should be in the range 60-80 cm3/min. The Ozone Flow can be adjusted by the
needle valve located on the back panel labeled “O3 Flow”. Once these flows have
been verified and adjusted they should not need to be re-adjusted unless the
instrument’s location changes in altitude. After adjusting the flow, the instrument
power should be cycled on and off before proceeding.

Model 405 nm NO2/NO/NOxMonitor Manual Rev. D
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3.3. Operation of the Monitor
To operate the NO2/NO/NOxMonitor, connect it to an external power source and
power the instrument on using the front panel power switch. The instrument requires
a 12 V DC source, which can be supplied by the provided 110-220 V AC power
adapter or an external battery. The power source should be capable of supplying at
least 2.5 amperes of current at 12 V (30 watts). The source can be in the range 11-14
V DC without any detrimental effects on the measurement. Note that the instrument
cannot be powered via USB connection to a computer because the minimum power
requirements cannot be achieved via this method. (Connection to the computer may
only used for data transmission; see Section 3.7.)
Once turned on, the instrument will display an introductory screen with the version
number of the firmware installed on the microprocessor and a display of the time and
date. After a few seconds, the instrument briefly will display a status screen showing
the state of logging (either the logged number, “OFF,” or “FULL”) and then begin
displaying measurements of the species selected for measurement (NO2; NO; or NO2
and NO) along with values of the cell flow rate (CF), ozone flow rate (O3F), and the
temperature (T) and pressure (P) of the absorption cell. Alternating screens will show
the Log state (logged number, OFF, or FULL) and the time and date. The first dozen
readings (requiring about two minutes) may be spurious, with large positive and
negative swings, due to the warmup of the light-emitting diode (LED) and electronics.
Also, measurements may be inaccurate during the first 10-20 minutes required for the
LED, photodiode, and internal temperature of the absorption cell to stabilize.
3.4. Connections and Setup
1. Attach the sample inlet line to the SAMPLE inlet port. The pressure of the sample
gas at the inlet port should be at ambient pressure and constant. The inlet tubing
should be made of PTFE (Teflon), PFA or some other inert material that does not
destroy NO2or NO and that does not desorb plasticizers and other organics that can
contaminate the flow path. The length of tubing should be kept as short as possible to
minimize loss of NOxspecies to the internal surface and to minimize reaction of NO
with ambient ozone. Tygon, polypropylene (which may look like Teflon) and metal
tubing should not be used. Teflon-lined Tygontubing, which is used inside the
instrument, provides the flexibility of Tygon with the inertness of Teflonand is
recommended. A provided Tefloninlet filter is required to prevent internal
contamination of the tubing and optical cell by particulate matter. We recommend a
47 mm PTFE (polytetrafluoroethylene) membrane filter with 5-micron pore size. Also,
particles can provide a positive interference to the measurement by absorbing and
scattering light from the LED source. The filter should be tested for NO2and NO loss
by measuring ambient NO2and NO with and without the filter attached. Replacement
filters are available through 2B Technologies. See our website: http://twobtech.com/parts-
online.html.

Model 405 nm NO2/NO/NOxMonitor Manual Rev. D
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2. Vent the EXHAUST port to atmospheric pressure and out of the room or shelter.
The monitor has an internal scrubber that removes ozone (produced to oxidize NO to
NO2) from the sample before exiting the instrument though the EXHAUST port.
However, it is recommended that the pump exhaust be vented to a well ventilated
area outside the room or shelter in case the scrubber fails.
If the instrument is being flown on an aircraft, the inlet tube should not point into the
wind, because the resulting pressure fluctuations will cause a noisy signal. Although
the instrument compensates for temperature drift, if strong temperature fluctuations
are expected, as in vertical profiling applications using balloons, the instrument should
be placed in a thermally insulated box in order to slow the rate of temperature change.
3.5. Measurement of the Zero Offset; Auto Zero Function
The electronic zeros for NO2and NO may be measured by attaching a NOxscrubber
to the air inlet for a period of 5-10 minutes. For an accurate measurement, the
instrument must have been turned on long enough for the internal temperature to
stabilize. The observed offset, which can amount to a few ppb, can be corrected by
changing this calibration parameter from the front panel, as described in Section 4.9
below, or by correcting the data at a later time.
The instrument also has an Auto Zero function. The instrument can be programmed
to periodically measure and apply new zero offsets for NO2and NO using an internal
NOxscrubber.
3.6. Collecting Data from the Analog Output
The data may be logged in real time using a data logger attached to the BNC analog
output. The range of the analog output is 0-2.5 V. The output is scaled according to a
sensitivity you define in the menu. For example, you may define 2.5V = 250 ppb. In
that case, the maximum output is 250 ppb, and 10 mV is equal to 1 ppb. There is a
small positive offset, typically 2 mV in the analog output, but this offset varies from
instrument to instrument. The offset can be measured by simultaneously observing
the panel display and measuring the analog output with a voltmeter.
3.7. Collecting Data over the Serial Port in Real Time
To transmit data to a computer over the serial port in real time, connect the instrument
to the computer using the 9-pin cable provided (and a serial-to-USB adapter cable if
necessary). Note that the 9-pin cable provided is a “straight-through” female-female
serial cable. A “cross-over” cable will not work. Start your data acquisition software,
preferably using the 2B Technologies Display and Graphing Software (free download
from http://twobtech.com/software.htm; see Appendix A for information on working
with this software). Other terminal emulation software such as HyperTerminal (a
program provided with earlier versions of Windows) or Tera Term may be used as

Model 405 nm NO2/NO/NOxMonitor Manual Rev. D
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well. Be sure to specify the baud rate setting of your data acquisition software to
match the baud rate setting of your instrument. Note that the baud rate of the
instrument may be set to 2400, 4800 or 19,200 as described in Section 4.11 below.
The NO2, NO and NOxmixing ratios (ppb, pphm, ppm), internal cell temperature (K or
°C), cell pressure (torr or mbar), volumetric flow rate (cc/min), date, and time are sent
as comma-delimited ASCII text to the serial port (2400, 4800 or 19,200 baud; 8 bits;
no parity; 1 stop bit) every 5 seconds, 1 minute, 5 minutes, or 1 hour, depending on
the averaging time selected from the microprocessor menu. Time is provided in 24-
hour (military) format, and the date is given in European style (day/month/year). The
user should separately make note of the instrument settings for units (NO2/NO/NOx,
temperature, pressure), baud rate and averaging time.
A typical data line might read:
67.4,44.2,111.6,-5,8,30.3,980.6,1576,76.2,1.2743,1.0151,110.2,12/10/15,18:31:27,80
where:
NO2= 67.4 ppb
NO = 44.2 ppb
NOx= 111.6 ppb
NO2_zero = -5 ppb
NO_zero = 8 ppb
Cell temperature = 30.3°C (may be expressed in K if chosen from menu)
Cell pressure = 980.6 mbar (may be expressed in torr if chosen from menu)
Cell volumetric flow rate = 1576 cc/min
O3volumetric flow rate = 76.2 cc/min
Sample photodiode voltage = 1.2743 volts
O3generator photodiode voltage = 1.0151 volts
Heated scrubber temperature = 110.2°C
Date = October 12, 2015
Time = 6:31:27 pm
Status = 80 (Measuring NO2and NO) (see Section 5 for status codes)
If the NOxMonitor has been set to the log data mode, the output serial data line will be
preceded by the log number; e.g.,
289,67.4,44.2,111.6,-5,8,30.3,980.6,1576,76.2,1.2743,1.0151,110.2,12/10/15,18:31:27,80
where 289 is the log number.
In addition to data lines, messages are written to the serial port when logging is begun
or ended, when transmission of data from the logger is begun and ended, when data
collection is interrupted (eh.g., due to a power failure) and when the averaging time is
changed.

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3.8. Data Averaging and Data Logging
When first turned on, the instrument will start making measurements at a rate of once
every 5 s (unless a different averaging time was previously chosen; see Section 4.5).
Internally generated data may be logged in the internal data logger. Up to 8,192 data
lines containing log number, NO2, NO, NOx, NO2_zero, NO_zero, Cell Temperature, Cell
Pressure, Cell Volumetric Flow Rate, Ozone Volumetric Flow Rate, Sample
Photodiode Voltage, O3Generator Photodiode Voltage, Heated Scrubber
Temperature, Date, Time, and Status may be stored in internal memory. Averaging
times of 5 s, 1 min, 5 min and 1 hr may be selected from the menu, thereby allowing
the instrument to operate for 1.4 days, 5.7 days, 1.0 months and 0.94 years,
respectively, before filling the memory.
3.9. Summary of Operating Recommendations
The following table gives a brief summary of operating recommendations mentioned in
this manual.
Operating Recommendation
Frequency
Section
Reference
Measure and adjust cell flow rate and ozone flow
rate before operating instrument (restart instrument
after adjustment of flows)
Whenever the instrument’s
location changes in altitude
3.2
Allow ~20 minutes for instrument warmup before
taking data
Each startup
3.3
Inlet tubing should be made of inert materials, such
as PTFE, PFA, FED, PVDF (do not use Tygon®,
polypropylene, or metal tubing)
Each use
3.4
Use a Teflon or PVDF inlet filter; test it for NO2and
NO loss
Each use
3.4
Vent exhaust to atmospheric pressure and out of
room or shelter
Each use
3.4; also
page 4
Check the span and zero offset; decide whether to
make use of the instrument’s Auto Zero function
Periodically
3.5, 7
Perform multipoint calibration
Annually
Any time major
disassembly of
components is performed
Any time the zero or span
checks give results
outside of the acceptable
limits
4, 7
If strong temperature fluctuations are expected,
place the instrument in a thermally insulated box
User-defined
3.4
During aircraft sampling, do not point inlet tube into
the wind
User-defined
3.4
Use adaptive filter if rapidly changing NO/NO2
concentrations are occurring or are anticipated
User-defined
1.2

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4. THE MENU
The instrument menu is accessed using the Select switch on the front panel of the
instrument.
To reach the menu, hold in the Select switch (for up to several seconds) until the
display shows: Menu.Then release the switch. The panel will now display:
Menu
Dat Avg Cfg Mod Zer 
where Dat, Avg, Cfg, Mod and Zer are submenus that may be selected. A blinking
cursor will show across the Dof the Dat submenu. The Select switch may be rotated
clockwise or counterclockwise to move the cursor under the first letter of one of the
other submenus. To select a particular submenu, move the cursor under the first
letter of the submenu and click (press in) the Select switch. To exit the Main Menu
and begin making measurements again, select and click on the left arrow (). Note
that “” always takes you up one level in the menu.
A diagram of the menu structure and detailed explanations of each of the submenus
are given below.

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4.1. Menu Tree
The following diagram summarizes the complete menu.
Main Menu
Dat Zer
1h5s
5m
Log
End
Xmt
D/T
Flow
1m
T/P NOxNO2
Bdr HrsVout
Cell_Flw O3_Flw
Mod
UntI/OCal
CfgAvg
NO
NO2 NONO2/NO
Dur Frq
LED