BAM 1020-9800 Manual Rev W.docx
Page 104
A final calibration is then performed on this BAM 1020. It is collocated with a reference BAM
1020 monitor. The collocated monitors then sample and measure the same aerosol (smoke)
for 48 or 72 hours. A linear regression of the hourly output of the BAM 1020 under test
against the transfer standard BAM 1020 wil
l provide a slope “
𝑘
” is used to set the final
calibration. This is shown in the equation below.
𝐶 = 𝑘
𝑚
𝑉
+ 𝐵𝐾𝐺𝐷
In this equation
𝐶
is the aerosol mass concentration in mg/m
3
,
𝑚
is the sampled mass in mg,
𝑉
is the sampled volume in m
3
, and
𝐵𝐾𝐺𝐷
is the instrument response in the absence of any
particulate matter as determined by the zero-filter test in mg/m
3
.
The span membrane response is in mg/m
3
and depends only on
𝜇
, the beta ray absorption
cross section, whereas C, the measured aerosol concentration in mg/m
3
depends on both
𝜇
,
𝑘
, and
𝐵𝐾𝐺𝐷
. Since sampled volume is also used in this calculation the accurate
determination of
𝐶
also depends on the ability of the equipment to accurately measure
volume.
11.1 Converting Data Between EPA Standard and Actual Conditions
The BAM 1020 is always sampling under actual flow conditions. The BAM 1020 may however
be set to report concentrations under either actual flow conditions or standard flow conditions.
The difference between these two values corresponds to the change in volume between a
BAM 1020 sample taken under actual conditions and that same sample taken under standard
conditions.
𝐶
𝑠𝑡𝑑
= 𝐶
𝑎𝑚𝑏
𝑃
𝑠𝑡𝑑
𝑃
𝑎𝑚𝑏
𝑇
𝑎𝑚𝑏
𝑇
𝑠𝑡𝑑
This equation can be used to calculate the standard concentration (C
std
) from the ambient
concentration (C
amb
) data using ambient barometric pressure and temperature data (P
amb
and
T
amb
) from the same time period in which the ambient concentration was recorded. P
std
and
T
std
are the values of standard barometric pressure and standard ambient temperature.
Please note that temperatures must be reported in degrees Kelvin and that standard
temperature may vary somewhat from one jurisdiction to another. It is usually either 273 °K or
298 °K.
𝐶
𝑎𝑚𝑏
= 𝐶
𝑠𝑡𝑑
𝑃
𝑎𝑚𝑏
𝑃
𝑠𝑡𝑑
𝑇
𝑠𝑡𝑑
𝑇
𝑎𝑚𝑏
This equation can be used to calculate the ambient concentration (C
amb
) from the standard
concentration (C
std
) data using the ambient temperature and pressure. It is necessary to have
