MONARCH INSTRUMENT Nova-Strobe PBL User manual

Nova-Strobe DBL
and
Nova-Strobe PBL
Deluxe and Phaser LED Stroboscopes
15 Columbia Drive • Amherst, NH 03031 USA
Phone: [phone] • Fax: [phone]
E-mail: [email protected]
Website: www.monarchinstrument.com
Instruction Manual

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Safeguards
and
Precautions
1. Read and follow all instructions in this manual carefully,
and retain this manual for future reference.
2. Do not use this instrument in any manner inconsistent
with these operating instructions or under any conditions
that exceed the environmental specications stated.
3. Certain strobe frequencies can trigger epileptic seizures
in those prone to that type of attack.
4. Users should not stare directly at the light source.
5. Prolonged exposure to the light can cause headaches
in some people.
6. Objects viewed with this product may appear to be
stationary when in fact they are moving at high speeds.
Always keep a safe distance from moving machinery
and do no touch the target.
7. There are no user serviceable parts in this instrument.
Refer service to a qualied technician.
8. Do not allow liquids or metallic objects to enter the
ventilation holes on the stroboscope as this may cause
permanent damage and void the warranty.

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9. Do not allow cables extending from unit to come into
contact with rotating machinery, as serious damage to
the equipment, or severe personal injury or death may
occur as a result.
10. This instrument may not be safe for use in certain
hazardous environments, and serious personal injury
or death could occur as a result of improper use.
Please refer to your facility’s safety program for proper
precautions.
11. Nova-Strobe LED units contain Nickel Metal Hydride
batteries which must be disposed of in accordance with
Federal, State, & Local Regulations. Do not incinerate.
Batteries should be shipped to a reclamation facility
for recovery of the metal and plastic components as
the proper method of waste management. Contact
distributor for appropriate product return procedures.
In order to comply with EU Directive 2012/19/EU on
Waste Electrical and Electronic Equipment (WEEE):
This product may contain material which could be
hazardous to human health and the environment. DO NOT
DISPOSE of this product as unsorted municipal waste.
This product needs to be RECYCLED in accordance
with local regulations, contact your local authorities for
more information. This product may be returnable to your
distributor for recycling - contact the distributor for details.
Monarch Instrument’s Limited Warranty applies.
See www.monarchinstrument.com for details.
Warranty Registration and Extended Warranty
coverage available online at
www.monarchinstrument.com.

iv
TABLE OF CONTENTS:
1.0 OVERVIEW .................................................................................. 2
1.1 LED Strobe Control Panel .................................................. 2
1.2 Modes of Operation ............................................................ 3
1.2.1 Internal Mode............................................................. 3
1.2.2 External Mode ........................................................... 3
1.2.3 Charging Mode.......................................................... 3
2.0 GETTING STARTED..................................................................... 4
2.1 Power ................................................................................... 4
2.2 Input / Output Connections................................................ 4
3.0 LED STROBE OPERATION ......................................................... 6
3.1 Adjusting the Flash Rate - RPM......................................... 6
3.1.1 Using the Knob........................................................... 6
3.1.2 Using the Keypad....................................................... 6
3.1.3 Decade Adjustment.................................................... 6
3.1.4 Multiply or Divide By 2............................................... 7
3.1.5 Fixed Increment N Adjustment ................................. 7
3.2 Adjusting the Flash Duration (Brightness)....................... 8
3.2.1 Flash Duration - Degrees........................................... 8
3.2.2 Flash Duration - Microseconds................................. 8
3.3 Display Units ....................................................................... 9
3.4 Tachometer Mode................................................................ 9
3.5 Mode Selection.................................................................. 10
3.6 Memory .............................................................................. 10

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3.7 Phase Delay ....................................................................... 10
3.7.1 Internal Phase Delay............................................... 10
3.7.2 External Delay (PBL Model ONLY)........................ 11
4.0 MENU..........................................................................................12
4.1 Decimal Places .................................................................. 12
4.2 Backlight ............................................................................ 12
4.3 Input Pulse Edge ............................................................... 12
4.4 Output Pulse Polarity........................................................ 13
4.5 Blanking ............................................................................. 13
5.0 STROBE BRIGHTNESS............................................................. 13
5.1 Calculating Blur................................................................. 14
5.2 Brightness in Degrees of Rotation .................................. 14
5.3 Brightness in Pulse Duration........................................... 15
6.0 USING THE STROBOSCOPE TO MEASURE RPM ................. 15
7.0 BATTERIES ................................................................................ 17
7.1 Low Battery Indication...................................................... 18
7.2 Charging the Batteries...................................................... 18
7.3 External Power Supply/Charger (PBL only).................... 19
7.4 Stroboscope Disposal ...................................................... 20
8.0 SPECIFICATIONS ...................................................................... 20
9.0 SENSORS, ACCESORIES, AND PARTS............................................ 22
Sensors and Accessories ........................................................ 22
Replacement Parts ................................................................... 23

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Figure 1 LED Strobe
Control Panel
1.0 OVERVIEW
The Nova-Strobe Deluxe DBL and Phaser PBL LED (Light Emitting Diode)
are rugged portable battery powered LED Stroboscopes used for inspection
and to stop motion to determine the speed of rotating objects. The units have
a pistol grip with lockable trigger switch and wrist strap for comfortable
hand held operation or they may be mounted on a tripod using the integral
¼ -20 UNC thread at the base of the handle. Although the DBL and PBL
are similar, the PBL has the additional ability to phase shift the image with
respect to an external signal and can animate the image in slow motion
rotation for inspection purposes. The PBL can also run continuously from
an external power supply.
1.1 LED Strobe Control
Panel
The Deluxe and Phaser LED
Strobes have a two line backlit
alpha-numeric liquid crystal
display (LCD) and a 12 key
keypad enables the user to
simply enter data and control
the operation of the unit. The
keys have dual functions – the
primary function is shown by
the black printing on the blue
background on the top half of
the key. The secondary function
is as a numeric keypad and the numerics are shown against a white
background on the bottom half of the key – 0 to 9, period and ENTER. The
LCD display has several icons which will be explained later in this manual.

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1.2 Modes of Operation
The stroboscope has two basic modes of operation – INTERNAL and
EXTERNAL.
1.2.1 Internal Mode
The strobe is in the Internal Mode when nothing is plugged into the
input jack or when manually set using the INPUT button. In the
internal mode the strobe generates its own timing signals and the
users can enter the ash rate using several different methods – see
Section 3.1.
1.2.2 External Mode
In the External Input Mode the user can’t make any ash rate
adjustments with the knob. The ash rate is a function of the input
signal. This mode is used to synchronize the ash to an external event
(for example, from an optical sensor) to stop or freeze motion. The
ash will be triggered on the rising or falling edge (menu selectable)
of the external input pulse. The strobe is in the External Input Mode
whenever there is a plug in the input jack. When the strobe is in the
External Input Mode, EXT will be displayed.
When an external input is applied to the unit and the strobe is put in the
Tachometer Mode, the unit will read the signal from the external input
(sensor) and display the reading on the LCD display without ashing
the lamp. The strobe will not ash in the Tach (Tachometer) Mode.
1.2.3 Charging Mode
The Charging Mode is when the strobe has the battery recharger
plugged into it. The strobe will continuously display the state of the
battery charge while being recharged.

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2.0 GETTING STARTED
The Stroboscope may be hand held or mounted on a tripod or other user
supplied bracket using the ¼-20 UNC bushing at the base of the handle.
2.1 Power
The LED Strobe is battery powered and has internal rechargeable
batteries. The unit should be charged before use (see Section 5.0). The
actual operating time of the stroboscope depends on the ash pulse width.
Narrower ash widths increase the operating time. Note that the DBL strobe
will not operate from the recharger supplied with the unit. The PBL will
run continuously from the supplied AC powered charger (PSC-PBXU).
To turn on the stroboscope, depress and hold the trigger. The trigger may
be locked in position using the side locking button. To lock the stroboscope
on, depress the trigger as far as it will go and then press the locking button.
Once the locking button is set you may release the trigger and the trigger
will be held in place. To unlock the stroboscope, simply depress the trigger
and then release.
NOTE: Unit must power down completely (OFF will be displayed and
then disappear) before unit will power on again. This is normal
operation. Wait 2 seconds before turning the unit back on again.
2.2 Input / Output Connections
The strobe has input and output jacks on the left side of the stroboscope.
These can be used for external triggering or synchronization (daisy-
chaining two or more strobes). These jacks accept 1/8” (3.5mm) phone
plugs (input - stereo, output - mono). The input and output signals are TTL
compatible. See Figures 2 and 3 for connector connection detail.

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Signal Input
+6V Out to Sensor
Common (GND)
Common (GND)
+6V Out to Sensor
Signal Input
Figure 2 Input Connector Detail (Stereo plug)
Pulse Output
from Strobe
Common (GND)
Common (GND)
Pulse Output
from Strobe
Figure 3 Output Connector Detail (Mono plug)
The input jack (pointing into socket) enables an external signal to
trigger the strobe. Inserting a plug into the input jack will automatically
put the strobe into the external mode. The INPUT button can be used to
toggle between External Input Mode and Internal Mode. When the plug is
removed, the strobe will be put back into the Internal Mode. The polarity
of the input pulse can be set in the MENU options. In the external mode
the knob cannot be used to change the ash rate.
With no external input, the output jack (pointing away from socket)
provides a TTL compatible pulse from the strobe’s internal oscillator.
If an external input is applied, the output pulse is in sync with the input
pulse. This output pulse may be used to trigger a second stroboscope
synchronously to illuminate larger areas. Many strobes can be “daisy
chained”. The output jack of one strobe is connected to the input jack of

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the next strobe causing all the strobes to ash together and be controlled
by the rst strobe in the chain. The polarity of the output pulse can be set
in the MENU options.
3.0 LED STROBE OPERATION
3.1 Adjusting the Flash Rate - RPM
There are several ways to adjust the ash rate of the Strobe:
3.1.1 Using the Knob
The ash rate can be adjusted by turning the knob on the side of the
unit – counter clockwise to increase the ash rate and clockwise to
decrease the ash rate. The knob is rate sensitive, the faster you turn
the knob the greater the change in ash rate. The smallest adjustment
is to add or subtract one from the least signicant (right most) digit
on the display.
3.1.2 Using the Keypad
It is possible to enter the required ash rate as a number
by entering the value using the keypad as you would with
a calculator. Press the NUMber key shown right followed
by the numeric keys representing the ash rate (eg 1234),
using the secondary key functions – numbers 0 to 9 and the
period, then press the ENTER button. Note: The system
will round the display to the nearest least signicant digit displayed.
If the display has no decimal places and you enter 1234.6 the display
will show 1235 and the strobe will ash at 1234.6 ashes per minute.
3.1.3 Decade Adjustment
The ash rate can be adjusted in decade steps eg: 1, 10, 100
etc. by pressing the button shown right. This will start a
digit on the display blinking. If the knob is turned this digit
will increment or decrement with rollover and roll under features.
Each time the button is pressed the blinking digit moves one
position to the right, the decade decreases by 10 until the digits stop
blinking. Pressing the button again will cause the left most digit
to start blinking.
To exit the decade adjustment mode while a digit is blinking press
any key other than the button.
3.1.4 Multiply or Divide By 2
The strobe ash rate can be instantly doubled (x2) or halved
(÷2) by pressing the x2 and ÷2 buttons shown right. This
is useful in determining actual rotational speed. Refer to
the section on speed measurement – Section 4.0. Note that
if doubling or halving the ash rate will cause the strobe
to exceed its capability, the display will show OVER or
UNDER respectively and the ash rate will remain at the current
ash value.
3.1.5 Fixed Increment N Adjustment
The strobe ash rate can be incremented or decremented
in xed increments. To do this, adjust the ash rate to the
required adjustment value, say 300, which we will refer to
as N. Then press the ±N button shown right (Note: – N is
the displayed value at the time the button is pressed). The display will
show ALT in the bottom left hand corner which indicates the knob is
in the ALTernate function mode. Turning the knob counterclockwise

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Each time the button is pressed the blinking digit moves one
position to the right, the decade decreases by 10 until the digits stop
blinking. Pressing the button again will cause the left most digit
to start blinking.
To exit the decade adjustment mode while a digit is blinking press
any key other than the button.
3.1.4 Multiply or Divide By 2
The strobe ash rate can be instantly doubled (x2) or halved
(÷2) by pressing the x2 and ÷2 buttons shown right. This
is useful in determining actual rotational speed. Refer to
the section on speed measurement – Section 4.0. Note that
if doubling or halving the ash rate will cause the strobe
to exceed its capability, the display will show OVER or
UNDER respectively and the ash rate will remain at the current
ash value.
3.1.5 Fixed Increment N Adjustment
The strobe ash rate can be incremented or decremented
in xed increments. To do this, adjust the ash rate to the
required adjustment value, say 300, which we will refer to
as N. Then press the ±N button shown right (Note: – N is
the displayed value at the time the button is pressed). The display will
show ALT in the bottom left hand corner which indicates the knob is
in the ALTernate function mode. Turning the knob counterclockwise
888888
> > > > > > > >

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will increase the ash rate by N (300 in this example) for each click
or turning it clockwise will decrease the ash rate by N. It is not
possible to decrement the ash rate below 30 FPM.
3.2 Adjusting the Flash Duration (Brightness)
The ash duration, the width of the LED ash, can be adjusted by the
user to be a preset number of degrees of rotation (DEGS) or a xed with
in microseconds (uSEC). The result is a more or less bright image at the
expense of less or more image blur. Read the section on Brightness -
Section 5.0.
3.2.1 Flash Duration - Degrees
To view or adjust the ash duration press the BRIGHT
button shown on the right. The display will show the
current ash duration in degrees of rotation – note that
there are 360° in a complete rotation. The degrees .
DEGS
shown is the amount of rotation visible during the
ash. The higher the degrees the brighter the image
and the more apparent the blur. Use the knob to
increase or decrease the ash duration in degrees of rotation. Adjusting
the degrees will cause this to be the controlling parameter for pulse
width. As the ash rate increases or decreases the strobe will adjust
the ash duration to keep it at the preset number of degrees provided
this does not exceed the strobe specications. Press any key other
than BRIGHT to exit or press BRIGHT again to go to
MICROSECOND adjustment.
3.2.2 Flash Duration - Microseconds
To view or adjust the ash duration in microseconds press
the BRIGHT button again after viewing degrees or press the
BRIGHT button twice from normal operation. The display
will show the current ash duration in microseconds (uSECS) – this

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may be calculated from phase degrees set above. Use
the knob to increase or decrease the ash duration
in microseconds. Adjusting the microseconds will
cause this to be the controlling parameter for pulse
width. As the ash rate increases or decreases the strobe will keep
the ash duration at the preset width in microseconds provided this
does not exceed the strobe specications. Press the BRIGHT button
to exit the ash duration adjustment.
3.3 Display Units
The display can show the ash rate in revolutions per minute
(RPM) or per second (RPS or Hertz). To switch between display
modes press the DISPlay button shown right. The display units
will toggle at each press (RPM < > RPS).
3.4 Tachometer Mode
The stroboscope can be used as a programmable pulse generator
or as a tachometer by pressing the TACH button shown right.
When an external input is supplied to the unit and the strobe is
put in the Tachometer Mode, the unit will read the signal from the external
input (sensor) and display the reading on the LCD display without ashing
the lamp. The TACH icon will show on the display. There is also
an ON TARGET INDICATOR shown right which illuminates
when a valid external signal is received.
If there is no external input and the TACH button is pressed the strobe
will stop ashing but will still output a pulse at the rate indicated on the
display. This rate may be adjusted as described in Section 3.1 above.
To exit the Tachometer mode press the TACH button again.

uSECS

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3.5 Mode Selection
The INPUT button, shown right, toggles between the
INTERNAL and EXTERNAL Modes as described in Section
1.2. When in the external mode the display will show EXT
and the stroboscope will only ash with an external input. Plugging
in an external source will cause the unit to automatically switch to the
EXTERNAL mode. Removing an external source while in the EXTERNAL
mode will cause the unit to switch to the INTERNAL mode.
3.6 Memory
The Stroboscope has the ability to save and recall up to 5 values.
This is done by pressing the MEMory button shown right. The
rst time the button is pressed the display will show READ , if
pressed again it will show SAVE . If the knob is turned while READ or
SAVE is displayed, the display will cycle through memory locations 1
to 5 (indicated as R M1 to RM5 where RM is Recall Memory or S M1 to SM
5 where SM is Save Memory). To actually SAVE or READ the selected
memory location, press the MEM button again. The ENTER button works
as well. The display will show DONE . Note that the value saved will be the
current ash rate prior to pressing the MEM button the rst time.
3.7 Phase Delay
The DELAY button adjusts the phase shift of the ash with
respect to time. There are two modes: INTERNAL and
EXTERNAL (PBL model only).
3.7.1 Internal Phase Delay
Also referred to as JOG. Once the ash rate has been adjusted to give
a stopped motion image, the PHASE DELAY button may be used to
increase or decrease the phase of the image with respect to its original
position. Use the PHASE DELAY button to bring a reference mark,
such as a key way, into your line of sight.

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To adjust the phase or jog the image, press the DELAY button. PHASE
will be displayed on the bottom line of the LCD display and the current
ash rate will be displayed on the top line. Turning the knob adjusts
the phase of the stopped image. It is a relative adjustment. Press the
DELAY button again to exit this mode.
3.7.2 External Delay (PBL Model ONLY)
The DELAY button has no function in External mode on the DBL
model stroboscope.
On the PBL model stroboscope there are three External Delay
Modes: Phase Delay, Time Delay,and Auto (Virtual RPM).These
modes are only active if an external trigger source is plugged into the
unit. The EXTernal icon must appear on the display.
Pressing the DELAY button cycles through the following modes:
In the External Phase Delay mode the ash is delayed 0.1 to 359.9
degrees after each external trigger pulse. The display will show
the delay in degrees on the top line and will indicate PHASE on
the lower line. The knob adjusts the amount of delay in degrees,
counterclockwise to increase and clockwise to decrease.
In the External Time Delay mode the ash is delayed 0.01 to 1000
msec after each external trigger pulse. The display will show the
TIME icon, the delay in milliseconds on the top line and will indicate
MSECS on the lower line. The knob adjusts the amount of delay in
milliseconds, counterclockwise to increase and clockwise to decrease.
In the Auto (Virtual RPM) mode the ash is automatically delayed
in increasing amounts after the external trigger pulse so that the
image appears to rotate at a slow (Virtual) speed, RPM. The display
will show the AUTO icon, the virtual speed in RPM on the top line

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and will indicate VRPM (Virtual RPM) on the lower line. The knob
adjusts the virtual speed in RPM, counterclockwise to increase and
clockwise to decrease.
4.0 MENU
The Menu allows settings of basic setup options – displayed
decimal places, backlight on or off, positive or negative edge for
input and output signal and blanking. The menu is entered by
pressing the MENU button and using the knob to scroll through the menu
options as described below. The top display line shows . To select a
menu option, press the MENU button again.
4.1 Decimal Places
Sets the number of decimal places shown on the display for numeric.
After pressing the MENU button rotate the knob until the display bottom
line shows DECPT and press the MENU button again. The top line of the
display will show the number of decimal places (2, 1, none) selected by
rotating the knob. Press the MENU button to select, then any other key
to exit. The display will show DONE and return to the normal readout.
4.2 Backlight
Enables the display backlight to be turned on or off. After pressing the
MENU button rotate the knob until the display bottom line shows BLITE
and press the MENU button again. The top line of the display will show 
or  selected by rotating the knob counterclockwise (yes) or clockwise
(no). The backlight will turn on and off accordingly. Press the MENU
button to select, then any other key to exit. The display will show DONE
and return to the normal readout.
4.3 Input Pulse Edge
Sets the input pulse edge that triggers the stroboscope. After pressing the
MENU button rotate the knob until the display bottom line shows INPUT

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and press the MENU button again. The top line of the display will show
the  (for positive edge triggered) or  (for negative edge triggered)
selected by rotating the knob counterclockwise (PoS) or clockwise (nEg).
Press the MENU button to select, then any other key to exit. The display
will show DONE and return to the normal readout.
4.4 Output Pulse Polarity
Sets the polarity of the output pulse. After pressing the MENU button
rotate the knob until the display bottom line shows OUTPT (Output) and
press the MENU button again. The top line of the display will show the
 (for positive edge triggered) or  (for negative edge triggered)
selected by rotating the knob counterclockwise (PoS) or clockwise (nEg).
Press the MENU button to select, then any other key to exit. The display
will show DONE and return to the normal readout.
4.5 Blanking
Blanking is used to reject the strobe’s own ash when using an external
optical sensor and prevent double triggering. After pressing the MENU
button rotate the knob until the display bottom line shows BLANK and press
the MENU button again. The top line of the display will show  or 
selected by rotating the knob counterclockwise (yes) or clockwise (no).
Yes enables blanking, no disables it. Press the MENU button to select,
then any other key to exit. The display will show DONE and return to the
normal readout.
5.0 STROBE BRIGHTNESS
The strobe’s brightness depends on how wide the LED ash pulse is; the wider
the pulse, the brighter the visual output from the LEDs. Since the strobe is
primarily used on reciprocating or rotating targets there is a downside to the
wider ashes. All strobes work by giving short bursts of light (the pulse width)
at a rapid repetition rate (the ash rate). Strobes rely on the persistence of the

14
human eye (the ability to remember and image) and its response to bright
light to give an apparent stop motion image. Imagine a shaft rotating at 6000
RPM or one rotation every 1/100 of a second (10 msec). If the strobe ashes
once every 10 msec for a brief moment, the user sees the ash at the same
spot in the rotation of the shaft and the persistence of the eye remembers this
until the next ash making the shaft appeared to be stopped. As the target is
rotating there is some movement evident during the strobe ash. The longer
the ash duration, the more obvious the rotation is and this increases the blur.
5.1 Calculating Blur
Blur can be calculated – if the shaft takes 10 msec to complete one
revolution and the strobe ash duration is 100 µsec (1/100 of a millisecond),
the shaft will turn:
(ash duration/time per rotation) x 360°, which is (.0001/.01) x 360 = 3.6°.
So you will see the shaft move 3.6°. As the ash pulse widens you will
see greater degrees of rotation which results in more blur and a brighter
perceived illumination (the LEDs are on longer so the average light the
eyes see is greater). The trade-off is blur versus brightness. One also has to
take into account tangential velocity (rotational speed) – the further away
the rotating point is from the center axis the faster the tangential velocity
and the worse the blur appears to be – it is always the same number of
degrees of rotation but the physical length of the blur gets bigger as the
point moves faster. The strobe adjusts the width of the pulse automatically
to keep the degree of rotation visible constant.
There are two methods of adjusting the ash pulse width and hence the
brightness and consequently the blur.
5.2 Brightness in Degrees of Rotation
The rst method is to adjust the ash pulse width for degree of rotation
visible (blur). The user can set this from 0.2 to 14 degrees out of 360. The
higher the setting the brighter the strobe appears to be but the more blurred

15
the target is. Optimal setting to stop motion is 1.8 to 3.6°. The number of
degrees is a proportional amount and remains constant as the ash rate
increases or decreases. The strobe automatically calculates how wide the
pulse width should be at different ash rates to keep the blur constant – the
faster the ash rate the narrower the pulse width. The pulse width equals:
(setting in degrees/360) x (1/ash rate in Hz).
Thus the blur remains constant no matter what the ash rate*.
5.3 Brightness in Pulse Duration
The second method is to adjust the ash pulse width to a xed number of
microseconds. Here the user sets the ash pulse width in microseconds
not degrees. As the ash rate increases the pulse width stays the same and
the image will get brighter and more blurred as the ash width remains
constant*. The degree of rotation visible changes to keep the pulse width
of the ash constant*.
*Note: There are two limits maintained by the strobe – the pulse can
never be greater than 3000 µs nor can it exceed 14° of rotation. The strobe
automatically adjusts these values as the ash rate is increased or decreased
to maintain these limits at all times. For example - at a ash rate of 600
ashes per minute 14° of blur represents a ash pulse width of 3800 µsec.
The Strobe will limit this value to 3000 µsec or 10.8° of rotation (blur).
6.0 USING THE STROBOSCOPE TO
MEASURE RPM
The primary use for a stroboscope is to stop motion for diagnostic inspection
purposes. However the stroboscope can be used to measure speed (in RPM
/ RPS). In order to do this several factors need to be considered. First, the
object being measured should be visible for all 360° of rotation (e.g. The
end of a shaft). Second, the object should have some unique part on it, like a

16
bolt, key way or imperfection to use as a reference point. If the object being
viewed is perfectly symmetrical, then the user needs to mark the object with
a piece of tape or paint in a single location to be used as a reference point.
Look only at the reference point.
If the speed of rotation is within the range of the stroboscope, start at a
higher ash rate and adjust the ash rate down. At some point you will stop
the motion with only a single reference point of the object in view. Note that
at a ash rate twice the actual speed of the image you will see two images
(reference points). As you approach the correct speed you may see three,
four or more images at harmonics of the actual speed. The rst SINGLE
image you see is the true speed. To conrm the true speed, note the reading
and adjust the stroboscope to exactly half this reading, or just press the ÷2
button. You should again see a single image (which may be phase shifted
with respect to the rst image seen).
For example, when viewing a shaft with a single key way you will see one
stationary image of the key way at the actual speed and at 1/2,1/3,1/4, etc, of
the actual speed. You will see 2 images of the key way at 2 times the actual
speed, 3 key way at 3 times, etc. The FPM equals the shaft’s Revolutions
Per Minute (RPM) at the highest ash rate that gives only one stationary
image of the key way.
Example: Object rotating at 3000 RPM
If the speed is outside the full scale range of the stroboscope (500,000
FPM), it can be measured using the method of harmonics and multipoint
calculation. Start at the highest ash rate and adjust the ash rate down.
You will encounter multiple images so be aware of these. Note the ash rate
Stopped Image 1/4 times 1/2 times 1 time 2 times 3 times 4 times
Flash Rate (FPM) 1000 1500 3000 6000 9000 12000
Actual RPM