6 Agilent ADM Flow Meter Operating Instructions
Principles of Operation
The ADM Flow Meter provides continuous, real time measurements of dry gas
flows, such as those used for Gas Chromatography. Unlike bubble flow meters, the
ADM Flow Meter operates without liquids, bubbles, or glass parts. When acti-
vated, a solenoid actuated valve interrupts the gas flow momentarily. The gas flow
moves a diaphragm in proportion to the flow rate. This movement is transformed by
the Flow Meter's electronics into a digital value which is displayed on the Flow
Meter's screen. The ADM Flow Meter provides two different types of flow mea-
surements: volumetric flow (mL/min) and mass flow reported in standard cubic
centimeters per minute (sccm). Mass flow values are calculated from the volumet-
ric measurements by correcting for ambient temperature and atmospheric pres-
sure, and reporting the flow rate referenced to 0 °C and 1 atmosphere of pressure,
using digital temperature and pressure sensors installed in the mainframe of the
flow meter.
The ADM Flow Meter employs a replaceable cartridge that contains all parts sub-
ject to calibration. This eliminates the need to ship the entire meter back to the fac-
tory to maintain its calibration. The cartridge calibration is valid for a period of one
year from its first use. A new, calibrated cartridge can be ordered in advance, and
then installed when necessary.
When the flow meter is powered on with a new cartridge installed, the current date
is written to the cartridge’s memory based on the mainframe’s internal clock. Each
time the flow meter is turned on, the meter will compare the current date to the ini-
tial turn on date of the cartridge. If the initial turn on date is more than a year from
the current date, the flow meter will flash a notification to the user that the calibra-
tion has expired. The flow meter will still function with an expired calibration. This
eliminates downtime, enabling you to keep working. See “Replacing the
Cartridge" on page 24.
CAUTION
The measurement calibration can be affected if the instrument
is exposed to temperatures above 50 °C for extended periods
of time.
Please inspect the temperature label attached to the inside of
cartridge packaging to verify that your cartridge has not been
damaged in shipment. A grey circle is acceptable, a black circle
indicates that the cartridge may have been exposed to an
extreme temperature.
Please contact Agilent Technical Support if your cartridge is
delivered with a temperature indicator that is black.
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