BAM 1020-9800 Manual Rev W.docx
Page 32
ACTUAL Flow Control:
FLOW TYPE should always be set to ACTUAL for firmware version 3.0 or greater. Under
actual flow control, ambient temperature and barometric pressure measurements are used to
convert the measured mass flow into volumetric flow (LPM). As the measured temperature
and barometric pressure change, the mass flow controller will adjust its output to maintain
constant volumetric flow. CONC TYPE may be set to ACTUAL in which case sampled
volume is reported in (actual) LPM sampled. CONC TYPE may also be set to STD, in which
case sampled volumes are adjusted and reported under standard conditions (25°C, 1 atm.).
STANDARD Flow Control:
This mode of operation is not recommended as the cut points for the PM
10
inlets and the
PM
2.5
size fractionators require a nominal flow of 16.70 actual liters per minute. All BAM 1020
monitors built since 2008 include a mass flow controller as standard equipment. External
temperature sensors (either BX-592 or BX-596) are required for mass flow control.
ACTUAL Flow Reporting
To report mass concentrations under actual conditions set
CONC TYPE
to
ACTUAL
. This
configuration is almost always used for PM
2.5
concentration reporting. It is also used when
reporting PM
10
concentrations when paired BAM 1020 monitors are used for PM
10
-
2.5
monitoring.
STD Flow Reporting
To report mass concentrations under standard conditions set
CONC TYPE
to
STD
. The BAM
1020 will then convert the actual volume sampled during the measurement cycle into the
corresponding standard volume and report the mass concentration under standard
conditions.
5.3 Total Flow (Q
TOT
) and Flow Rate (LPM) Conversions
The Q
TOT
measurement can be converted to LPM by multiplying the Q
TOT
value by 1000, then
dividing by the BAM Sample Time. For example, to determine what the flow rate was of a 42
minute sample with a Q
TOT
value 0.700, perform the following calculation:
(Q
TOT
* 1000) / Sample Time = (0.700 * 1000)/42 = 16.67 LPM
5.4
About Leak Checks, Nozzle Cleaning, and Flow Checks
Met One Instruments recommends that users perform leak checks, nozzle and vane cleaning
(if needed) and a flow check or calibration (if needed) at least once a month. Complete flow
system maintenance typically requires less than 10 minutes to perform.
The best order for the monthly flow system checks is:
1.
As-found leak check.
2.
Nozzle and vane cleaning.
3.
As-left leak check. (If a leak was corrected)
4.
Three-point flow check/audit and calibration if required.
If an air leak is found it almost always occurs at the interface between the nozzle and the filter
tape due to debris buildup. There is normally an insignificant amount of leakage at the tape
interface, but an excessive leak lets an unknown portion of the 16.70 L/min sample flow to
enter the system at the leak point instead of the inlet. This could cause the total volume of air
sampled through the inlet to be incorrect, and the resulting concentration data could be
