skcinc.com
Form 37171 Rev 200630
Page 21
Setting/Calibrating Flow Rate from 100 to 1000 ml/min
— Constant Pressure Mode
(No All-in-One or CPC required)
About Constant Pressure Mode
In Constant Flow mode, the pump adjusts to the set flow and maintains it by directly measuring the flow.
In
Constant Pressure mode
, the pump will adjust to the set inlet pressure and maintain it for the duration
of the sampling run. Flow through the sampling train depends on set pressure and overall pressure drop
in the sampling line. Flow rate can be increased or decreased by adjusting inlet pressure
– higher inlet
pressure will correspond to higher flow and vice versa. For a set inlet pressure value, flow will remain
constant if resistance in the sampling line remains constant during the entire sampling period.
Constant Pressure mode may be conveniently used with single and multiple-tube holders; in some
situations, the single tube can be connected directly to the pump without a tube holder for sampling at
flows as low as 100 ml/min. Although Constant Flow mode is recommended if sampling requires a flow
higher than 1000 ml/min, the pump can be used in Constant Pressure mode for flows up to 5 L/min if the
pressure drop does not exceed 20 inches H
2
O. To use the pump in Constant Pressure mode, the
pressure drop across the sampling train should be between 1 and 20 inches H
2
O.
Note: The pump will
not work in Constant Pressure mode without a sampling medium connected to its inlet
.
Set Pump in Constant Pressure Mode
Before setting/calibrating pump flow in Constant Pressure mode, connect the sorbent tube or other
sample medium to the pump inlet.
See Figure 6
.
Note: The pump will fault if there is no sample medium or
if the load is too low.
From Sample Menu:
Touch
left/right arrow buttons
to set gross pressure setting.
Touch
up/down arrow buttons
to fine-tune setting.
Note: A
sustained touch on the up/down arrow buttons will
increment/decrement pressure setting.
Note: Set pressure value will blink and left LED will blink yellow-
orange. When set pressure is achieved, the pressure value will
stop blinking and the left LED will turn green. This may take up to
90 seconds.
Touch check mark to accept selection and return to Constant
Pressure screen.
Touch Advanced
>Touch
pressure display
