Personal Ozone Monitor Manual Rev. E-2
8
plasticizers and other organics that can contaminate the flow path. The length of
tubing should be kept as short as possible (preferably not more than a few feet) to
minimize ozone destruction within the inlet tubing. Tygon
, polypropylene (which may
look like Teflon), and metal tubing should not be used. FEP-lined Tygon tubing, which
is used inside the instrument, provides the flexibility of Tygon with the inertness of
FEP. A Teflon or PVDF inlet filter is highly recommended to prevent internal
contamination of the tubing and absorption cell by particulate matter. The filter should
be tested for ozone loss by measuring ambient ozone with and without the filter
attached. Filters and filter holders are available through 2B Technologies.
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.
3.3.
Measurement of the Zero Offset
The electronic zero of the instrument may be measured by attaching an ozone zeroing
scrubber (2B Technologies part no. ZEREXTPOM or other ozone destruction cartridge) 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 for by changing the
offset calibration parameter (Z) from the front panel, as described in Section 5.10 below.
3.4.
Collecting Data over the USB Port or Serial Port in Real Time
To transmit data to a computer over the USB port or the serial port in real time,
connect the Personal Ozone Monitor to the serial port of the computer using the
stereo plug to D9 serial cable provided. Start your data acquisition software,
preferably using the 2B Technologies Display and Graphing Software (available as a
free download from
http://twobtech.com/downloads_software.htm
; see Appendix A for
a description of 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 well.
The ozone mixing ratio (ppb), internal cell temperature (K), cell pressure (torr), time,
and date are sent as comma-delimited ASCII text to the serial and USB ports (19200
baud as selected in the menu; 8 bits; no parity; 1 stop bit) every 2 seconds, 10
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).
A typical data line would read:
3.2,307.4,608.1,1.2740,12.1,4001.27765,-10513.0308,1591.20,1,23/03/12,16:39:14
where:
Ozone = 3.2 ppb
Cell temperature = 307.4 K
