6.0 Operating Instructions
The following pages will guide you through the operation of your DC-Lite primary
flow calibrator.
6.1 DC-Lite Button Panel
5
4
Unit Indicator
ml
•
Milliliters per minute
L
•
Liters per minute
Single Flow Reading
Average Flow in
Sequence
(10 readings maximum)
Print Status
Off
•
Turns off Parallel Port output
10
•
Prints 10 readings and stops
All
•
Prints all readings
5.0 Theory of Operation
The DryCal DC-Lite is a primary standard. The time required for the graphite com-
posite piston to traverse a known distance within the glass flow cylinder
(cell) is precisely measured, and an internal computer calculates the flow. The
volumetric accuracy of the instrument is built into its dimensional characteristics.
The DryCal, like other piston provers, is characterized by the most basic of quanti-
ties: length and time. Because flow is necessarily a derived unit, a dimensionally-
characterized system would be as close as possible to direct traceability from
national dimensional standards.
An idealized piston prover would consist of a massless, frictionless, leakproof,
shape-invariant and impermeable piston inserted within the flow stream and
enclosed by perfect cylinder. The time the piston takes to move a known distance
(which implies a known volume) yields the volumetric flow as:
q = v / t =
π
r
2
h / t
Where
•
q
= volumetric flow rate
•
v
= measurement volume
•
t
= measurement time
•
r
= radius
•
h
= measurement path length
This piston prover would be as accurate as its physical dimensions and its clock,
with almost insignificant drift mechanisms. Although such idealized devices do not
exist, we believe the DryCal offers close to ideal performance.
When a flow reading begins, the DryCal's internal valve closes, diverting gas into
the glass flow cylinder (cell) for measurement. The piston rises–at the rate of gas
flow between two finely-collimated light beams of known distance apart (Point A
and Point B). After a suitable acceleration period, the rate of piston travel between
Point A and Point B is timed. As the piston passes Point B, the flow reading ends,
the valve opens, the gas is released, and the piston drops (resets). The gas is
allowed to pass directly through the DryCal, bypassing the flow cell until the next
reading begins. The volumetric flow measurement, based upon the parameters of
length and time, is instantly displayed on the LCD in mililiters per minute (ml) or
liters per minute (L).
Battery Status
•
Full
•
Mid-Level
•
Low
6.2 Turning the Power On
The DC-Lite has an energy saving 5-minute auto shut-off feature.
1
Press the
On
button to turn the DC-Lite on.
2
An initializing screen will display the microprocessor revision number,
then the standard screen will be displayed.
