iii?
w
Fig. 2 explains the electronic part. It consists of a
pulse generator and a control unit. The two corre
sponding printed circuits are placed in a small box,
that serves the following actions: start/stop, rota
tion left/right, and speed regulation. The velocity
of the star to be observed should be first adjusted
on a calibrated scale and the movable wire set in
the start position. When the star reaches the
movable wire in the field of view, the observer starts
the motor and keeps subsequently the movable wire
in coincidence with the star. This is done by means
of the large knob. In neutral position of this knob
the wire moves with the nominal velocity of the
star, turning the knob to the left the velocity
decreases (min. 0), turning to the right the
velocity increases (max. twice the nominal veloc
ity).
3 Investigation of the motor-micrometer using
an artificial star
The accuracy of the motor-micrometer was investi
gated using an artificial star as shown in Fig. 3. The
star is simulated by an illuminated fine diaphragm
mounted on a carriage. This carriage is moved by
a synchronous motor via a wormgear over a range
of about 0.5 meter. The direction of the motion is
reversed automatically by microswitches at both
ends of the rail of the carriage.
In order to control the position of the artificial star,
two reference points are selected near the ends of
the star's path. When the star passes these reference
points, an electric pulse is produced by a photocell,
stable
multi
vibrator
MOTOR
GENERATOR
CONTROL
UNIT
92340
range fine
Nominal
velocity
adjustment
Velocity
regulation
Fig. 1. Kern DKM 3A with motor-micrometer.
1. step motor; 2. contra weight; 3. ocular; 4. nominal
velocity adjustment; 5. direction of rotation: left/
right; 6. velocity regulation; 7. start/stop; 8. input
12 Volt D.C.; 9. on/off; 10. D.C. indicator; 11. con
nector for the chronograph; 12. connector for step
motor and mechanical contacts; 13. connector for
frequency counter (calibration); 14. illumination; 15.
resistance for illumination.
Fig. 2. Block diagram of electronical part.
Fig. 3. Artificial star
1. frame for guidance; 2. illuminated diaphragm;
3. synchronous motor and transmission; 4. disc with
slit; 5. photocell; 6. photocell pulse indicator;
7. microswitch; 8. relay; 9. resistance for brightness
("magnitude").
50
ngt 73
