Calibration Check; Proceed As Follows - Perkins Mk2 Manuel D'instructions

en
11.

Calibration Check

Regular calibration of the Tonometer is advised.
Please see 7.3 Special Precautions
The calibration of the tonometer should be checked at regular intervals or at any time when
the practitioner feels that an immediate spot check is desirable.

Proceed as follows:-

1. Remove the battery handle (11 Fig 2) from the tonometer by pressing the two handle
securing buttons (10 Fig 2) and withdrawing it from the body portion. Insert the prism
into the holder (4 Fig 1).
Check for zero position
2. Adjust the milled thumb-wheel (8 Fig 2) so that the scale reading is below zero by the full
thickness of one scale line. Whatever the attitude of the instrument in the hand the prism
should tend towards its backward position.
3. Set the scale reading above zero by the full thickness of one scale line. The prism should
tend towards its forward position regardless of the attitude of the tonometer.
Check at the 2 g position
4. To make a rough check adjust the milled thumb-wheel (8 Fig 2) so that the scale reading
is below the 2 mark by the full thickness of one scale line. Place the instrument on a flat
horizontal surface with the setting block under the body and the prism cone upwards as
shown in Fig 16. Place the 2 g weight, recess downward, centrally on the prism cone and
check that it carries the prism positively down to its lowest position.
5. Also, as a rough check, set the scale reading above the 2 mark by the full thickness of
the scale line and place the instrument on the setting block as before. Place the 2 g weight
on the prism and check that it remains in its highest position.
(If the prism is accidentally pushed down to its lowest position with the weight on the prism,
it should rise again to its highest position and freely remain there).
Battery case
removed
If desired, the Actual point of balance can be established by adjusting the milled
thumb-wheel (8 Fig 2) until the prism floats at the calibration-position (rim of prism holder
level with, or not more than 1 mm above the case surface).
29
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(
Fig 15)
Weight
Fig 15
scale reading
2
Setting
Block