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Upon pressing the START key, the motor will turn on, and the display will indicate the
“warm-up delay”, if enabled. The display will then indicate the current totalized volume,
the current flow rate, and the elapsed time (volume mode) or remaining time (time
mode). i.e.:
ft3 CFM Time or lit LPM Time
123.4 4.5 12:34 12345 123 12:34
If the FLOW RATE reading is blinking during sample collection, it is because the unit is
running at a flow rate outside of its calibrated range. This can be corrected by
recalibrating the unit.
The unit will continue to sample unit the target time or volume has been reached, or until
the STOP key is pressed. Upon completion or termination of a sample, the display will
indicate the final time/volume of the sample. i.e.:
Volume: 123.4 ft3
Run Time: 12:34
NOTE: In the event that power is disconnected or turned off prior to completion of a
sample, the elapsed time/volume will be displayed upon power-up. The CLEAR key
must be pressed to clear the last run and again display the originally set target volume.
When using the Model H-810BL with the optional tripod for breathing zone sampling
applications (See Appendix C), please note the adaptor or tripod mounting block may be
installed on the bottom or the front of the unit. When the adaptor is mounted on the front,
the keypad display is most accessible.
PRINCIPLE OF OPERATION
The principle of operation of the air volume totalizer is very simple and basic in nature.
Theoretically, a fan mounted on a freely turning shaft will rotate at a rate proportional to
the velocity of the air passing the fan. This velocity is proportional to the flow rate,
assuming the pressure differential across the filter media stays constant, and the ambient
air temperature/pressure stays constant. By measuring the fan RPM for a number of flow
rates, a nearly linear response can be generated between the airflow rate and the fan
speed.
RADēCO tested the above principle and learned that the above was true within limits.
We found that for each filter media, the turbine speed was close to linear, but only over a
limited flow range. The CFM versus RPM curve also varied depending on the pressure
drop of different filter media. For any given filter media, we found that by using a three
