1.0 INTRODUCTION
The BGI PQ100 is an "Intelligent Air Pump" that can monitor it's own airflow rate and thereby
adjust the pump speed to compensate for changes in load pressure and/or other forces which
would otherwise hamper the flow of air through a filter (or sample collector). The PQ100 can be
programmed to begin it's sampling job at a specific date and time and stop sampling after the user
defined run time is depleted. A 24 character by 2 line Liquid Crystal Display provides the
operator with a readout of flow rate, and other useful information.
Events such as the flow being restricted by blocking the inlet, batteries depleted (power failure),
pump unable to regulate flow (excess resistance), etc. all force the pump into a shutdown mode
which consumes no battery power until the problem causing the shutdown is corrected.
The PQ100 was designed to operate from 1 standard liter per minute (1000 cc per minute) to 25.0
standard liters per minute and is unaffected by changes in ambient temperature and barometric
pressure. The flow rate precision is guaranteed 2% of the calibration set point. Standard
conditions, for some forms of air sampling, being 20ΕC, 760 mm of Mercury barometric
pressure.
Certain default values in this instrument have been selected to reflect EPA style air sampling
procedures. The default "Run Time" is 24 hours. The default "Start Date and Time" is midnight
tomorrow.
Principle of Operation
The operating principle of the PQ100 can be appreciated by referring to the block diagram below.
Air is drawn by the pump through a size selective inlet device and/or filter. It then passes inside
the instrument housing to a Mass Flow Sensor. The signal generated by the sensor is then routed
to a microprocessor which determines if the flow is at the set value and adjusts the pump speed to
maintain the correct flow rate. Because the flow sensor is extremely sensitive and all pumps
produce pulsation to some degree, a pulsation damping volume has been introduced to control
this effect. The microprocessor not only controls the flow rate accurately and precisely to the set
point but also performs several other functions. These include turning the instrument on at a
preselected time and running it for a selected interval. The flow is maintained by the processor to
a designated pressure and temperature value. A pulse width modulated signal is configured and
sent to the pump motor in a constantly updated manner based on signal information received
from the Mass Flow Sensor. The microprocessor also stores all parametric information
generated during the run period and configures it for presentation on the visual display and
downloading to the software provided with the instrument.
The system is completed by it's 12 volt battery and external battery charger/A.C. power supply.
The power supply function permits operation if desired with no battery whatsoever.
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