1 presetting the max/min calibration points, Calibration – American Magnetics 185 & 186 Liquid Level Instruments (CE-Marked) User Manual

Page 32

Rev. 3

Calibration

Closed dewar calibration

3.3.2.1 Presetting the MAX/MIN calibration points

The following procedure should be performed before installation of the

sensor in the target cryo-vessel.

1. Connect the extension and oscillator cables to the J5 coaxial

connector on the rear panel of the instrument (see page 7 for a

system diagram). Do not connect the sensor. Energize the

instrument. Press the MIN push-button through the small hole

provided on the instrument front panel. When the calibration point

has been accepted, the display will show "bbb.b" and the push-

button can then be released.

2. Connect the sensor to the oscillator cable (which is still connected

to the instrument via the extension cable). Press the MAX push-

button through the small hole provided on the instrument front

panel. When the calibration point has been accepted, the display

will show "bbb.b" and the push-button can then be released.

3. Calculate the factor C

adj

using the following equation:

where L

total

is the total sensor length in inches, L

active

is the active

sensor length in inches, and e is the dielectric constant of the target

liquid.

4. Enter C

adj

into the instrument by placing the front panel control

mode rotary switch in the SILENCE position. By using the RAISE/

LOWER toggle switch and holding it in the up or down position,

adjust the displayed value up or down. The display will move slowly

at first and then faster. Once near the desired value, simply release

the switch momentarily and then resume changing the factor at the

slower speed. Once the desired number has been reached, release

the toggle switch.

5. Once the value for C

adj

has been entered, momentarily press the

CAL push-button labeled as "~" (the tilde character) through the

small hole provided in the instrument front panel. When the value

has been accepted, the display will show "ddd.d" and the button can

then be released.

6. With the sensor connected, again press the MIN push-button

through the small hole provided on the instrument front panel.

When the calibration point has been accepted, the display will show

"bbb.b" and the push-button can then be released. The presetting

procedure is complete. Proceed to the remainder of the closed dewar

calibration procedure as presented below.

adj

120 1

2.1 L

active

(

)

5.2 L

total

(

)

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–

0.454

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