NPZ 1PN91-2, Service Manual

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the needle from the plane with index (checking aiming circle according to
the height); checking of the deviation of the needle from the zero position
(checking of the standstill angle); checking of the decay time and number of
oscillations of the needle.
First, checking the aiming circle according to the direction and height is
done; then, the standstill angle, the standstill time and number of oscillations
of the needle are checked.
3.3.2 Before checking and adjusting of the aiming circle, it is necessary to
do the following:
– level the angle measuring device 4 (Figure 2) according to the round level 6
(Figure A.4) carefully;
– aim the observing line of the sighting device at the checkpoint the direction
of which (magnetic azimuth) is known beforehand;
– loosen the scale 7 by turning the handle 6 and set the reading on it corresponding
to the magnetic azimuth. Fix the scale 7 by turning the handle 6;
– set the reading 0-00 on the scale 7 by turning the handwheel 8. The
observing line of the sighting device is directed to the North.
3.3.3 If the aiming circle 4 needle does not coincide with the index, superpose
the needle with the index by turning the handwheel 8.
If the reading on the scale 7 is less than ±0-0, the aiming circle need not be
adjusted according to the direction.
If the reading on the scale 7 is more than ±0-0, it is necessary to do the
following:
– loosen the screws 8 (Figure A.4) and 9 with the help of the spanner 7
(Figure A.9) and turn the aiming circle 4 till the needle coincides with the
index. Fix the screws 8 and 9.
Check the coordination of the aiming circle according to the direction using
the methods given in the point 3.3.2.
3.3.4 If the needle of the aiming circle 4 does not coincide with the index
more than on 0.5 mm when the checking procedure from the point 3.3.3 is
carried out, it is necessary to do the following:
– loosen the screws 2 (Figure A.4) with the help of the spanner 7 (Figure A.9).
Superpose the needle with the index according to the height up to the value
of not less than 0.5 mm by turning the aiming circle in the vertical plane. Block
up the screws 2.
3.3.5 The standstill angle, the rest time and the number of oscillations of the
aiming circle needle are checked after the works described in the points 3.3.3
and 3.3.4. For this do the following:
– draw a small steel object to the aiming circle 4 case. The aiming circle
needle must deviate till touching the case side;
– draw the steel object away. The needle must oscillate at least 6 times and
stop oscillations maximum within 50 sec. After the oscillations, the aiming circle
needle must return to its original position (reading 0-00 on the scale 7);