3. OPERATION
Page 107
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significant difference between the pressure measured by the at its reference level
and the pressure actually present at the molbloc at a different height. In this case, it is useful
to make a head correction to the pressure measured by the in order to predict the
pressure actually applied at a different height.
can calculate
head
pressures for all the gases it supports (see Section 3.4.2),
over its working pressure range. The HEAD function allows the difference in height between
the and the molbloc to be specified and causes the resulting head pressure to be
added to the pressure measured at the rear panel quick connectors.
[SPECIAL]
,
<8head>
, is used to specify the height difference between the rear
panel quick connectors and another height. Entering a height of zero turns the function off.
Note
Use of the HEAD function to assure in tolerance measurements is most
important when using molbloc-S at high pressures. Specifying the head
height within ± 3 in. (7.5 cm) is adequate to assure that, even in the worst
case, the uncertainty on the head correction will be insignificant relative to
the tolerance of the measurement.
OPERATION
To access the HEAD function, press the
[SPECIAL]
,
<8head>
. The display is:
1.
Entry field for head height.
2.
Current gas selection.
Edit head height:
+ 25 cm N2
Edit the head height to the desired value. Press
[ENT]
to return to the run screen with the
new head correction active. Press
[ESC]
to return with no changes.
Note
The reference height of the
pressure measurement is the middle of the
rear panel pressure quick
connectors. The head height should be
entered as a positive value if the molbloc is
higher than the and negative if it
is lower.
Note
•
The HEAD function is NOT channel specific. The HEAD height setting and
ON or OFF status remains the same as molbloc channels are changed.
•
When a head correction is being applied, it is indicated by <h> to the right
of the pressure unit in the [P&T] screen (see Section 3.4.5). When the head
correction is zero, the <h> is not shown.
•
The head function is automatically disabled when running AutoZ (see
Section 3.4.4.4.2) and in the calibration run screen (see Section 5.2.4.1).
3.6.9
<9BPR>
PURPOSE
In molbloc-S operation, to select the BPR (back pressure ratio) measurement mode. The
S BPR measurement mode is always on; there is no option to turn it off or use the
auto selection option described below.
PRINCIPLE
