Manual

31
Calibration
Calibration Menu Reference
3.3.4 Select Calibration Sub-Menu
If the
option is chosen as documented in paragraph 3.3.3, then the
operator is presented with the following menu selections. The
key can
be used at any point to exit the sub-menu.
3.3.4.1 Select active calibration
The select active calibration menu allows the operator to select one
of up to four previously performed calibrations as the “active”
calibration. The active calibration is used for all measurements for
the given sensor input. The asterisk
in the display indicates that
a calibration has previously been performed and is available for
selection as active. Use the
key to move the cursor.
Selections are valid immediately and will affect level measurements
for the channel assigned to the sensor input. Use the
key to
continue.
3.3.4.2 Approximate calibration factor
The approximate calibration selection menu provides options for
transforming a calibration in liquid nitrogen to any of four common
liquefied gases under saturated conditions at 1 atm. The
approximate calibration factor is a ratiometric value that relates
the dielectric of the liquid used to perform the actual calibration to
another liquid (or the same liquid under different conditions) for
level monitoring/control. The actual values used for the
approximate factors are listed in Table 3-1 below.
Table 3-1. Pre-defined approximate calibration factors for
common cryogens at 1 atm relative to LN
2
.
Cryogen
Factor
a
a. From NIST Database 12 for saturated liquids at 1 atm.
Para-Hydrogen (LH
2
) 53.00
Oxygen (LOX) 112.3
Argon (Ar) 122
Natural Gas
b
(LNG)
144.5
A: Select Active
$1*2*3 4
A: Approx Factor
$None LH2 LOX