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SECTION ONE
INTRODUCTION
1.1 OVERVIEW
The Gilian Gilibrator 2 Calibration System is an easy-
to-use Primary Standard for the calibration of air
sampling equipment. The system includes a high
accuracy, electronic flowmeter that provides
instantaneous air flow readings and cumulative
averaging of multiple samples. Three Wet Cell
Assemblies provide a wide range of flow rates and
are easily interchangeable using twist-on/off
mounting.
A crystal-controlled microprocessor Control Unit is
designed for accurate data readings. A dual function
DELETE/RESET button on the Control Unit subtracts
erroneous readings to ensure accurate data, or can
cancel the current readings completely.
A 9-pin male RS-232 serial port on the Control Unit
allows you to output the sampling results to a printer,
computer, or compatible sampling pumps and
docking stations. A USB-B interface on the Control
Unit allows output to a computer. Windows™
compatible Gilibrator 2 Flow Monitoring Software is
available that allows you to collect, store, and plot
flow samples.
Features of the Gilibrator 2 Calibration System
include an easy-to-read display; simultaneous
display of flow rate, flow average, and number of
samples taken; dis- play indicators for LOW BAT,
WAIT; and automatic power shutoff when the unit is
inactive for 15 minutes. You can also specify the
number of samples to be taken (5 to 95) in 5 sample
increments.
Gilibrator 2 Calibration System Kits include a Wet
Cell Assembly, Control Unit Base (CE approved),
USB wall-power adapter, USB cable (for battery
charging and communication), Tubing, and Soap
Solution & Dispenser.
Interchangeable Flow Cell Assemblies are available
as follows:
•Low Flow Wet Cell (1 to 250 cc/m)
•Standard Flow Wet Cell (20 cc/m to 6 LPM)
•High Flow Wet Cell (2 to 30 LPM)
1.2 THEORY OF OPERATION
To be a primary standard, all values must be
absolute and measured as absolute. A primary
standard airflow measurement is a volume divided by
a time interval as performed by the Control Unit of
the Gilibrator 2. The volume (V) is measured volume
of space between two beam-break infrared
sensors. The time (t) is that interval needed for the
soap film bubble to travel between the two sensors
which bound the volume. Thus, the volume per unit
of time (V/t) becomes the flow rate. Because the
electronic clock is far more accurate than the
volume measurements, the volume measurement
accuracy determines the overall accuracy of the unit.
The Gilibrator 2 consists of two elements, the Wet
Flow Cell Assembly and the Control Unit Base. The
function of the Flow Cell Assembly is to provide a
means for measuring the soap film bubble traveling
up a flow tube through a known volume of space.
Measurement of the travel time is done by means of
“top” and “bottom” infrared sensors mounted along
the flow tube. The volume bound by these sensors
is set accurately to a primary volume standard.
As the bubble moves up the tube, it trips the bottom
sensor. As it moves further up the tube, it trips the
top sensor. The time difference between the bottom
and top sensors becomes the elapsed travel time.
This timing information (along with the volume
information) is sent to the microprocessor in the
Control Unit Base. The calculated flow and sample
information are then displayed directly on the Liquid
Crystal Display.
