13900-103 Rev. A Page 25
Calibration (Continued)
Pressure Delivery (Ramp) Calibration:
This test provides instructions for measurement of the air
puff solenoid drive current.
1. While in the Services Menu screen, press the button
beneath the DOWN ARROW icon until "CAL./VER." is
highlighted. Press the button beneath the SELECT
icon.
2. Press the button beneath the DOWN ARROW icon
until "SOLENOID" is highlighted. Press the button
beneath the SELECT icon.
3. After the unit puffs, a graphical representation of the
pressure ramp will appear on the screen. The graph
line must pass through the "alignment dots" on the
screen. Refer to Figure CT-1.
If the applanation curve does not pass through the
"dots", remove the Tonometer Head Cover and adjust
the potentiometer which is labeled "SOLENOID
CURRENT ADJUST" on the tonometer circuit board
until the curve passes through the "alignment dots" on
the screen. To generate a new curve, press the
button below the DEMO icon. Refer to Figure CT-2.
Repeat as required.
4. Press the button beneath the "RETURN" icon.
Fixation Alignment
This test provides instruction regarding the alignment of
the fixation spot which the patient observes during
measurement.
View the green fixation spot through the air tube. Refer to
Figure CT-3 for an illustration of the fixation spot. This
green spot should appear centered and near the back of
the tube. If the green spot is not round or has a reflection
around the perimeter of the spot, the position of the circuit
board must be adjusted.
To adjust the position of the circuit board, perform the
following:
1. If the Tonometer Head Cover was not removed, you
must remove the cover to perform the steps below.
2. Loosen the 2 screws that secure the fixation PCB
assembly to the nosepiece assembly.
3. Look through the airtube assembly and tighten the
circuit board when the green spot is round, centered
and does not have a reflection. Refer to Figure CT-4.
NOTE: If the green fixation spot cannot be adjusted so
that the spot is round and has no reflections,
remove the circuit board from the tube housing
and slightly adjust the position of the diode
torwards the direction of the shadow.
Figure CT-1. Pressure -vs-Time Waveform
Figure CT-2. Solenoid Current Adjustment Potentiometer
Figure CT-4. Fixation Spot Shadow
Figure CT-3. Fixation Spot
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