HP 5890 Series II Plus Reference Manual page 62

Electronic Flow Sensing
Electronic flow sensor (EFS) calibration
3. Locate the EFS module and note its labelling: CHANNEL A/
CHANNEL B, IN/OUT. For the channel being calibrated, locate and
disconnect its OUT fitting; use two wrenches in opposition to prevent
twisting the tubes.
Figure 4-2
Outlet Line, Channel B
EFS Module
Detail, Electronic Flow Sensor (EFS) Module
4. Install the EFS flow•measuringadapter (Part No. 05890•80620)into
the female OUT fitting to the EFS module. Connect a bubble flow
meter to the adapter.
Allow ample time (up to 1/2•hour)for residual gas within connected
plumbing to bleed off. Verify that absolutely no flow is observed at
the connected bubble flow meter.
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Outlet Line, Channel
A