switch bar knob to the 4000 25,000 RPM position and wrap the power
cord clockwise around the knob and reflector. Secure the power-cord
plug by sliding the ground terminal of theplug onto the holder pin (10,
Figure 1-1). Lift the instrument until it is free to pivot on the handle
and lower it into the case.
2-4. TURNING INSTRUMENT ON.
The following precautions should be observed before turning the
a. Before plugging the power connector into a power receptacle,
make certain the power corresponds to the data on the plate above the
power cord on the panel.
b. The power plug has three terminals. For operator safety, the
third pin on the power plug must be properly grounded.
Pivot the reflector assembly to an upright position and snap the
power switch on. The stroboscope will be ready for use in about 10 seconds.
2-5. POSITIONING THE STROBOSCOPE.
The light beam can be aimed in almost any direction by means of
the swivel arm and the rotating reflector. The intensity of the light pulse
is so high that it is usually not necessary to place the unit very close
to the object being viewed. If the instrument is to be held for a long time
the neck strap can be used to provide added support. The neck strap can
be adjusted to any one of three lengths. To install the strap, slip the
appropriate slots in the strap over the buttons projecting from the side
of the case.
2-6. ADJUSTING THE FLASHING RATE.
The flashing rate of the strobotron lamp is adjusted by means of
the RPM control. To operate this control, grasp the fluted transparent
rim which surrounds the range mask. The over -all frequency range of
the Stroboscope is divided into three overlapping ranges, selected by the
range -switch bar knob. Windows on the range mask reveal only the range
in use. A red line inscribed below the RPM dial indicates the frequent y
setting in flashes per minute (corresponding to rpm) for speed measure -
ments. The frequency limits for each range are marked near the appro -
priate window. The range switch has no limit stops and can therefore be
rotated continuously. The rotation of the RPM control, however, is limited
to 300 degrees by stops.
If the instrument is to be used for speed measurements, the RPM
dial should be calibrated with respect to the power -line frequency. The
Type 1531 Strobotac will normally remain calibrated for a considerable
period of time, unless significant changes occur in ambient temperature
or in the power -line voltage.