Section 5: Integrated Gas Sampling
Airmetrics
41
during a single pulse, a 10 second interval between pulses would result in 6 cc
being pumped per minute, or 360 cc per hour, or 1440 cc over four hours. Since
this amount falls considerably short of 6 liters, the pulse duration and/or frequency
would have to be increased accordingly.
In this manner, calculate an approximate pulse duration and pulse frequency for the
test period.
NOTE: New samplers are factory calibrated to deliver 1 cc per pulse.
Preparing the Sampler
1.
Attach a new battery pack.
Important Note:
The Valve Sequencing Board automatically resets when
the sampler's main power is interrupted. Conseque ntly, the battery must
be changed
before
setting the s equenc ing circuit.
2.
Unscrew either cap of the bale assembly bar and remove the bale assembly.
3.
Disconnect canister tubing and remove the can isters.
4.
Lift the pump a nd timer assem bly out by the 6" diameter top ca p and suppo rt
the mounting board on the edge of the sampler casing using the pump mount
stand and taking care not to pull the connecting wire loose. Hold the top cap
and do not grasp the center of the circuit board. Leave the battery attached.
5.
Set the calculated pulse duration for the test period with the Pulse Duration
Contro l.
6.
Set the interval between pulses to the calculated setting by turning the
Intervalometer F requency A djustment. Th e control is marke d 0-9 then A-F
where zero is continuous pulsing and F is one pulse eve ry 15 seconds.
7.
Turn on the valve sequen cer board by mo ving the P ower O N/OF F Switc h to
the UP position. Note that the other four dip switches (which control the pulse
duration) are activated in the down position.
8.
Set the Valve Driver Board to either standard or overlap mode using the
Airmetrics MiniVol Users Guide
42
Airmetrics
Figure 5.2.
Installing Tedlar® Bag
Overlap Jum per.
9.
Program the timer for the desired test period.
10. Set the timer to "Auto" to begin the test period.
11. Replace the pump and timer assembly into sampler body. Replace the 6" cap,
the bale assembly bar, and the canisters. Reattach the canister tubing.
12. At the end of the test period, increase or decrease the pulse frequency or pulse
duration depending on the fullness of the bags.
13. When test results are within adequate limits, attach new battery pack and move
sampler to field site.
I
NSTALLING
T
EDLAR
®
B
AGS
AND
A
TTACHING
C
ANISTERS
Four Tedlar® bags, protective
canisters, and tubing are provided
for gas sam pling. Th e bags atta ch to
the canister top caps with bulkhead
fittings, to w hich tubin g is
connec ted on the outside tha t runs to
the mini quick-connects on the
sampler bod y (see Figure 5.2 ).
Before attaching the canister to the
sampler, the bags should be
completely evacuated.
1.
Evacuate ba gs using either a
small vacuum pump or the
sampler pump. Connect the bag
tubing to an inlet side of the
sampler pump, and run the
pump in particulate matter
sampling mode until bag is flat
and empty.
2.
Rem ove the sh ort bale ass embly bar and in sert the long er canister b ale
