PASCO SF-9211 STROBOSCOPE - Manual (Page 6)

2
Stroboscope 012-02119C
General Operations
Plug in the stroboscope to a standard 117 volt outlet using
the supplied power cord. Flip the power switch to ON.
The power switch will light, the stroboscope will begin
flashing, and the display will read the flash rate in flashes
per second. To vary the flash rate, turn the FLASH RATE
ADJUST knob located to the right of the display (clock-
wise increases the rate; counterclockwise decreases the
rate).
The LEDs below the display indicate the mode of
operation. When the unit is turned on, the top LED will
always light, indicating the display is reading in flashes
per second. Pressing the switch located to the left of the
LEDs changes the display units to RPM. Pressing the
switch again will change the mode to External Trigger. In
this mode the stroboscope will only flash if an appropriate
external trigger is provided. Pressing the switch a third
time will return the stroboscope to automatic flash with
the display reading in flashes per second.
Using The External Trigger
As already mentioned, the external trigger can be used to
synchronize the strobe flashes with another stroboscope
or with some external event. Banana plug connectors are
provided for hookups operating in this mode. As labeled
on the control panel of the stroboscope, the output signal
is a 5 volt pulse and the external trigger requires a pulse
from 3-50 volts. (As is standard, the black connectors are
a common ground.)
To trigger the stroboscope from an external event it is
necessary to provide a 3-50 volt pulse that is coupled with
the event. Connect this input to the EXT. TRIG. connec-
tors on the control panel of the stroboscope. (Connect the
signal to the red connector, the signal ground to the
black.) Turn on the stroboscope and switch it to the
External Trigger mode. The stroboscope will now flash
on the descending edge of every trigger pulse.
When operating in external trigger mode, the display
shows the flash rate in flashes per second. Since the unit
must count the flashes over each one second period, the
flash rate is given only to the nearest integer. (The flash
rate reading in this mode is only accurate for flash rates of
at least 10 flashes per second.)
To synchronize the flashes of two stroboscopes, simply
use the OUTPUT signal from one stroboscope to supply
the external trigger for the second. If more than two
synchronized stroboscopes are needed, the output from
the second may be used to trigger a third, and so on. A
daisy-chain of stroboscopes hooked up in this manner
will all flash simultaneously in sync with a flash from the
first. The flash rate of the first stroboscope may be
adjusted manually , or it may be coupled to some other
external trigger.
Using The Stroboscope as a Tachometer
The stroboscope offers an easy method for accurately
measuring the frequency of rotation of a mechanical
system. To do this, mark a convenient point on the
rotating device. Beginning with a flash rate that is clearly
higher than the frequency of the rotating device, adjust
the flash rate until the mark on the device appears station-
ary. The stroboscope display will then show the fre-
quency of rotation. (If the initial flash rate is not clearly
higher than the frequency of rotation, care must be taken,
as the mark will appear stationary whenever the fre-
quency of rotation is a higher harmonic of the flash rate.)
Operation