TURNING INSTRUMENT ON.

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

stroboscope on:

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.

Self Test.

2.7.1 GENERAL.

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.