– 4 –
4.0 O
PERATION
4.1 True RPM Measurement
DT311A/315A stroboscopes are DUAL function instruments that give the
operator the illusion of “stopped motion” where in actuality the equipment
under observation is in a moving state. By adjusting the flash rate,
equipment in motion appears to be standing still. With a slight adjustment,
movement can be viewed in apparent slow motion, which enables the
operator or observer to study the process in action. All DT311A/315A
stroboscopes can measure rotational (RPM) or reciprocating (strokes per
minute) speeds with the same high precision as with an electronic digital
tachometer.
To measure true revolutions per minute (RPM):
1. “Mark” the object to be measured by either visually noting an inherent
distinguishing characteristic (such as a label, scratch, etc.) or physically
marking the object with a small piece of tape, pencil mark, etc.
2. Firmly plug in power cord.
3. Turn power switch on.
4. Turn setter from highest FPM
downward.
5. The true RPM can be noted once
the action appears frozen and the
first single image of the “mark”
appears (see chart below and
accompanying diagram for
further explanation).
6. To verify RPM reading, press
“÷2”; a single image should
appear again.
Rotation of shaft
(rpm)
Number of
flashes (rpm)
Flashes/
rpm shaft
Number of
stopped images
at
1,500 rpm
6,000
4 times
4
4,500
3 times
3
3,000
2 times
2
1,500
1 times
1
750
1/2 times
1
500
1/3 times
1
– 9 –
7.0
F
LASH
T
UBE
R
EPLACEMENT
When FPM reading is displayed but unit is not flashing, flash tube may need to
be replaced:
1. Unplug line cord from power line (DT-315A).
2. Turn power switch off
IMPORTANT:
Wait a few minutes until stroboscope is cool before replacing
flash tube.
3. Remove protective window by removing the
4 screws.
4. Use tube removing tool provided: insert tool
all the way and turn clockwise until tool locks.
Pull out tube.
5. Install new flash tube using the removing tool.
IMPORTANT:
Do not let the flash tube come in
contact with bare skin, use a rag when handling.
NOTE:
Make sure that the tube is placed vertically
in the socket (see diagram below) otherwise it will
touch the reflector. Tube should be set symetrically
within the neck of the reflector.
6. Replace protective window.
7. Mount reflector in the center so that the
reflector will not interfere with the screw spacer
on the corners.
