– 6 –
– 15 –
Step 2:
As the flash rate was lowered, three singular harmonic images were found.
(The first image at 9,600 RPM is rejected because it is a double image).
Point "X" is 7,200, point "Y" is 4,800 and Point "Z" is 3,600.
Step 3:
To calculate the true RPM, enter these values into one of the equations
shown on the next page. For this example, we will use equation (6).
RPM
= 2AB(A+B)/(A-B)2
= 2x2,400x1,200x(2,400+1,200)/
(2,400-1,200)2
=
14,400
Where A = (X-Y)
= 7,200 - 4,800
= 2,400
And B = (Y-Z)
= 4,800 – 3,600
= 1,200
Therefore, the true speed of the object is 14,400 RPM. To help further illustrate this
point, the figure below shows the harmonic relationship of the four images found in
this example:
If TWO points, “X” and “Y” are
recorded:
(1) *RPM = XY/(X-Y)
(2) *RPM =Sx(Sx+1)(X-Y)
(3) RPM =S (S -1)(X-Y)
(4) *Sx = Y/(X-Y), rounded
(5) Sy = X/(X-Y), rounded
If THREE points, “X,” “Y” and “Z”
are recorded:
(6) *RPM = 2AB(A+B)/(A-B)2
(7) *A= (X-Y)
(8) *B (Y-Z)
Variations of THREE point formulas:
(9) *RPM = 2PS/D2
(10) P = Product, (A*B)
(11) S = Sum, (A+B)
(12) D = Difference, (A-B)
(13) *Sx = 2(Y-Z)/(X+Z-2Y)
(14) Sy = (X-Z)/(X+Z-2Y)
(15) Sz = 2(X-Y)/(X+Z-2Y)
(16) *Sx = 2B/(A-B)
(17) Sy = (A+B)/(A-B)
(18) Sz = 2A/(A-B)
(19) Sx = 2B/D
(20) Sy = S/D
(21) Sz = 2A/D
Depending on the accuracy desired, either two or three harmonic points can be found.
These points are used in one of the following equations:
Formulas for calculating “Out of Range” RPMs.
Harmonic
FPM/RPM
1/4
1/3
1/2
2/3
5/6
1/1
3,600
4,800
7,200
9,600
12,000
14,400
6.0 SIMPLE
OPERATION
1.
Be sure to charge the internal battery before first use.
2.
Aim the PK2 at the moving object and turn it on. There will be a delay of 1–2
seconds before the flash begins to operate. If the LOW BAT symbol in
the display is illuminated, charge the battery.
3.
Adjust the flash rate by rotating the Flash Adjustment Knob until the image appears
motionless (as you approach the movement frequency, the image appears to move
more slowly). This value will be shown in the LCD display.
IMPORTANT:
Motionless images do not only appear when the movement frequency
is reached, but also when multiples and fractions of the movement frequency are
reached.
For additional information on visually slowing down the motion of an object as well as
using your Pocket-Strobe as a tachometer, please refer to the appropriate section(s)
later in this manual.
Helpful Hints:
■
Dim the ambient lights for best results.
■
The flash frequency for which the image of the object appears with the greatest
contrast is the movement frequency.
5.0 INFORMATION ON BATTERY MANAGEMENT
Several factors effect the battery life:
■
The warmer the operating environment, the shorter the battery life; the cooler the
environment, the longer the battery life.
■
The more times the battery is completely drained, the shorter the battery life.
Helpful Hints:
To maximize the life of the battery:
■
Shut the instrument off intermittently in order to allow the battery to recover.
■
Allow the instrument to cool down if the outside temperature is hot.
■
Keep the battery fully charged. Do not allow it to completely drain between
charges.
■
When storing the unit at room temperatures, charge/discharge it once every three
months.
