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Option, Menu, Calibration – American Magnetics 286 Multi-Sensor Liquid Level Instrument (CE-Marked) User Manual

Page 45

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31

Calibration

Calibration Menu Reference

3.3.4

Select Calibration Sub-Menu

If the

Select

option is chosen as documented in paragraph 3.3.3, then the

operator is presented with the following menu selections. The

ESC

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

OPTION

key to move the cursor.

Selections are valid immediately and will affect level measurements
for the channel assigned to the sensor input. Use the

MENU

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