PASCO ME-8930 User Manual

Instruction Manual and
Experiment Guide for the
PASCO scientific
Model ME-8930

SMART TIMER

012-06734A

09/98

Plane4

© 1998 PASCO scientific $7.50

Smart Timer 012–06734A

01206734A Smart Timer

Table of Contents

Section Page

Table of Contents ..........................................................................................................................i

Copyright, Warranty, and Equipment Return ................................................................................ ii

Introduction ................................................................................................................................. 1

Equipment ................................................................................................................................... 3

Operating the Smart Timer .......................................................................................................... 4

Smart Timer Modes of Operation ................................................................................................ 4

Quick Cross-Reference for Suggested Activities and Smart Timer Modes .............................. 5

Time Modes ....................................................................................................................... 6

Speed Measurement Modes ................................................................................................. 7

Table 1: Summary of Timing Modes................................................................................ 89

Acceleration Measurement Modes ..................................................................................... 10

Count Modes .................................................................................................................... 10

Test Mode ........................................................................................................................ 11

Timing Diagrams ................................................................................................................ 11

LOCK Switch: ................................................................................................................... 11

Caring for the Smart Timer ........................................................................................................ 12

Specifications ............................................................................................................................. 12

Accessory Options ...................................................................................................................... 12

Troubleshooting ........................................................................................................................ 14

Experiment One: Acceleration of Gravity ................................................................................... 15

Experiment Two: Newtons Second Law ................................................................................... 17

Experiment Three: Conservation of Momentum In Collisions .................................................... 19

Experiment Four: Conservation of Angular Momentum ............................................................. 25

Other Suggested Experiments ..................................................................................................... 31

Technical Support ......................................................................................................... back cover

i

Copyright, Warranty, and Equipment Return

PleaseFeel free to duplicate this manual
subject to the copyright restrictions below.

Copyright Notice

The PASCO scientific 012-06734A Smart Timer
manual is copyrighted and all rights reserved. However,
permission is granted to non-profit educational
institutions for reproduction of any part of the manual
providing the reproductions are used only for their
laboratories and are not sold for profit. Reproduction
under any other circumstances, without the written
consent of PASCO scientific, is prohibited.

Limited Warranty

PASCO scientific warrants the product to be free from
defects in materials and workmanship for a period of
one year from the date of shipment to the customer.
PASCO will repair or replace at its option any part of
the product which is deemed to be defective in
material or workmanship. The warranty does not
cover damage to the product caused by abuse or
improper use. Determination of whether a product
failure is the result of a manufacturing defect or
improper use by the customer shall be made solely by
PASCO scientific. Responsibility for the return of
equipment for warranty repair belongs to the
customer. Equipment must be properly packed to
prevent damage and shipped postage or freight
prepaid. (Damage caused by improper packing of the
equipment for return shipment will not be covered by
the warranty.) Shipping costs for returning the
equipment after repair will be paid by PASCO
scientific.

Equipment Return

Should the product have to be returned to PASCO
scientific for any reason, notify PASCO scientific by
letter, phone, or fax BEFORE returning the product.
Upon notification, the return authorization and
shipping instructions will be promptly issued.

ä

NOTE: NO EQUIPMENT WILL BE

ACCEPTED FOR RETURN WITHOUT AN
AUTHORIZATION FROM PASCO.

When returning equipment for repair, the units must
be packed properly. Carriers will not accept
responsibility for damage caused by improper
packing. To be certain the unit will not be damaged in
shipment, observe the following rules:

➀ The packing carton must be strong enough for the

item shipped.

➁ Make certain there are at least two inches of packing

material between any point on the apparatus and the
inside walls of the carton.

➂ Make certain that the packing material cannot shift in

the box or become compressed, allowing the
instrument come in contact with the packing carton.

Address: PASCO scientific

10101 Foothills Blvd.
Roseville, CA 95747-7100

Phone: [phone]
FAX: [phone]
email: [e-mail]
web: www.pasco.com

ii

012–06734A Smart Timer

Introduction

The PASCO ME-8930 Smart Timer is an accurate, versatile digital timer and
measurement system for the student laboratory. The Smart Timer offers 0.1 ms timing
resolution and an easy-to-use memory function. The Smart Timer measures several types
of events detected with PASCO’s digital sensors, including speed and acceleration using
standard photogates. The PASCO ME-9387 Smart Pulley, the ME-9207B Free Fall
Adapter, the ME-6810 Time-of-Flight Accessory, or the ME-9259A Laser Switch also
work with the Smart Timer. The Smart Timer counts radiation emission events detected
with the SN-7927 G-M Tube/Power Supply or the SE-7997 G-M Tube. The Smart Timer
features two input channels and a 2-line, 16-character alphanumeric liquid crystal display
that indicates the operating mode and experimental results.

Features:

The Smart Timer’s memory function makes it easy to time events that happen in rapid
succession, such as a Dynamics Cart passing twice through the photogate, once before
and then again after a collision. The 0.1 ms resolution is especially useful in some
experiments, such as measuring velocity or acceleration during free fall. The Smart
Timer can calculate velocity before and after a collision between two carts using a single
timer. With the new fence design and sensing logic, parallax errors are eliminated and
timing accuracy is improved considerably over existing timing options. The Smart
Timer’s internal microcontroller also eliminates the problem of incorrect readings due to
multiple passes through the same photogate by “understanding” the type of measurement
selected and ignoring multiple passes.

The Smart Timer has many different options for timing and calculating values based on
inputs from a variety of sensors. The graphics on the keypad aid in the selection of the
appropriate timing mode. Options include One or Two Gates, Fence, and Pendulum
modes. These modes allow you to measure the speed of an object as it passes through the
photogate or between two photogates, or to measure the period of a pendulum. The
stopwatch mode lets you use the timer as an electronic stopwatch.

The Smart Timer can measure speed and acceleration for both linear and rotational
motion experiments. Alternatively, the time can be measured directly, and the speed and
acceleration can then be calculated by the student. The speed and acceleration
measurement features can be enabled or disabled using a switch inside the Smart Timer.

Use With Photogates:

The Smart Timer is optimized for use with PASCO’s ME-9204B Accessory Photogate
(available separately). These narrow-beam infrared photogates plug directly into the
Smart Timer and are used to provide the timing signals. An LED in one arm of the
photogate emits a narrow infrared beam. As long as the beam strikes the detector in the
opposite arm of the photogate, the signal to the timer indicates that the beam is
unblocked. When an object blocks the beam so it doesn’t strike the detector, the signal to
the timer changes.

1

Smart Timer 012–06734A

In One Gate Mode, a single photogate lets you measure the time, velocity, or acceleration
of a fence as it passes through the photogate. Two photogates are used for collision
experiments using one or two carts or for experiments where the velocity of a cart must be
measured at two different points. In Two Gate Mode, two photogates are used and the
time to travel between the two can be measured. This mode can also be used to measure
time of flight using the ME-6810 Time-of-Flight Accessory.

Use with the Smart Pulley:

For rotary motion studies, the ME-9387 Smart Pulley (available separately) is ideal. It
combines a photogate with a pulley, and when used with the Smart Timer, allows direct
measurement of angular speed and acceleration. When used with a string connected to a
glide or Dynamics Cart, the Smart Timer and Smart Pulley can be used to determine

2

linear acceleration (cm/s

) as well.

➤ Note: The use of pulleys with different diameters and/or different number of spokes
than the Smart Pulley or the ME-9450 Super Pulley will give incorrect results in the speed
and acceleration calculations.

Power Options:

The Photogate Timer can be powered using the included 9VDC adapter. It will also run
on 4-AA size, 1.5 volt alkaline batteries which will provide over 100 hours of operation in
typical use.

Experiments:

Four copy-ready experiments and 9 additional suggested experiments are included in this
manual, showing a variety of ways to use the Smart Timer. The equipment requirements
vary for different experiments. For many of the experiments, you will need a Dynamics
Track and Dynamics Carts. Some experiments also require two ME-9204B Accessory
Photogates or the ME-9387 Smart Pulley. Check the equipment requirements listed at the
beginning of each experiment.

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012–06734A Smart Timer

Equipment

Included:
Smart Timer
Smart Timer Picket Fences (2)
9 VDC adapter

mode illustrations

liquid crystal display

connector for 9VDC adapter
(side panel))

on/off switch
(side panel)

touchpad keys

Plane4

input channel 2

input channel 1

9 VDC adapter

battery compartment
(bottom panel)

5 cm fence

1 cm flag

1 cm fence

Figure 1

Included equipment

Smart Timer Picket Fence

Smart Timer Picket Fence

Smart Timer Picket Fences

3

Smart Timer 012–06734A

Plane4

Operating the Smart Timer

input channel 2

input channel 1

1. Plug the ¼-inch phone plug from the photogate into the

Smart Timer’s input channel 1 or 2 (see Figure 2). For all
experiments using a single photogate or pulley, either of the
two available jacks may be used interchangeably. For all
other modes see the individual descriptions below.

2. Plug the 9 VDC power adapter into the small receptacle on

the side of the timer and into a standard 110 VAC, 60 Hz
wall outlet.

3. Position the photogate head so the object to be timed will

pass through the arms of the photogate, blocking the
photogate beam. Loosen the clamp screw if you want to
change the angle or height of the photogate, then tighten it
securely.

4. Slide the power switch to the ON position. The Smart
Timer will “beep” and show PASCO scientific on the
display. From this point, the three-step setup of the Smart
Timer is easy:

1. Press the Select Measurement key until the

desired measurement type is displayed on the top
line of the display. Note that the menu rolls over to
the beginning after the last type is selected.

2. Press the Select Mode key until the measurement

mode is displayed after the measurement type.
You cannot begin a measurement until both the
type and mode have been selected.

3. Once a complete measurement has been selected,

press Start/Stop to begin. You will hear a “beep”,
and a asterisk (*) will appear on the second line of
the display. In most modes, the (*) indicates that
the Smart Timer is now waiting for an event to
occur, like a fence passing through a photogate.

5. If an event occurs, the Smart Timer beeps again, displays a
result, and the (*) disappears. Pressing Start/Stop before an
event occurs will remove the (*) and allow you to change
the measurement type.

Figure 2

Connecting the photogate to the Smart
Timer

➤ Note: Smart Timers shipped to certain
locations are supplied with a transformer
for 220/240 VAC, 50 Hz power.

ä

Important Setup Note:

The Smart Timer incorporates a feature to
increase the battery lifetime. The photogate
turns on only when Start/Stop is pressed
to start an experiment. Photogate power is
turned off when the measurement is
complete or the operator presses Start/
Stop. The exception is the Test mode in
which photogate power is turned on as
soon as the display reads Test:Gates and is
not turned off until Select Measurement is
pressed again. Setup for the experiment is
often best accomplished in Test:Gates
mode.

Smart Timer Modes of Operation

The Smart Timer has 18 modes of operation organized into five
groups: Time, Speed, Acceleration, Counts, and Test. A

4

012–06734A Smart Timer

5

Smart Timer 012–06734A

summary of the mode suggested for a given experimental activity can be found on page 5
(Quick Cross-Reference for Suggested Activities and Smart Timer Modes). Refer to the
timing diagrams in Table 1 (pages 8 and 9) for a detailed look at how the Smart Timers
times events on its input(s) and an explanation of how speed and acceleration calculations
are performed internally.

The following are detailed descriptions of the Smart Timer’s modes of operation.

Time Modes

One Gate: In One Gate mode, timing begins when the beam is first blocked and
continues until the beam is blocked again. This mode can be used to measure the speed of
an object as it passes through the photogate. If an object of length L blocks the photogate
for a time t, the average velocity of the object as it passed through the photogate was L/t.

Fence: In Fence mode, the timer measures the time between successive interruptions of
the photogate. Timing begins when the beam is first blocked and continues until the
beam is unblocked and then blocked again. The Smart Timer can remember ten such
interruptions and will allow the user to scroll through the times using either the Select
Measurement or the Select Mode keys. Pressing the Start/Stop once will allow another
measurement type to be selected. Pressing it twice begins a new Fence Mode
measurement. Note that once a measurement has begun with an initial block of the
photogate, the Smart Timer will continue to time until ten interruptions are counted before
stopping the measurement and displaying the result. Pressing Start/Stop will stop the
measurement, and any recorded times will be displayed.

➤ Note: The
picket fence
supplied with the
Smart Timer is
designed to
increase timing
accuracy when
used with
photogates. The
fence has three
sections: the 1 cm
flag, the 5 cm
fence, and the 1
cm fence; one of
these must be
aligned with the
photogate light
path before the
experiment can
proceed.

Two Gates: In this mode, the Smart Timer measures the time between blocking two
photogates. This mode is useful for not only air tracks and Dynamics Tracks but also with
the ME-6810 Time-of-Flight Accessory. In this mode, you must plug the photogate you
expect to encounter first into input channel 1, and the second photogate into input
channel 2.

Pendulum: In Pendulum mode, the timer measures the period of one complete
oscillation. Timing begins as the pendulum first cuts through the beam. The timer
ignores the next interruption, which corresponds to the pendulum swinging back in the
opposite direction. Timing stops at the beginning of the third interruption, as the
pendulum completes one full oscillation. Press the Start/Stop key again to begin a new
timing cycle.

Stopwatch: The Manual mode is actually a dual-use function. It provides a means of
manually timing events (like a using a Stopwatch) by pressing the Start/Stop key. It also
allows timing of events using the ME-9207B Free-Fall Adapter and the ME-9259A Laser
Switch, which function via a block/unblock sequence.

Using the Stopwatch: Enter Stopwatch mode and press the Start/Stop key. The
Smart Timer will beep and a “*” will appear on the second line of the LCD. Press
the Start/Stop key again to start the timer. Press the Start/Stop key to stop timing
and display the elapsed time. Press the Start/Stop key again. The old result is

6

012–06734A Smart Timer

cleared and the “*” reappears. This RESET-START-STOP sequence is repeated for
each new elapsed time. Whenever the “*” is not showing, the mode may be
changed.

Using the Alternate Timing Function: Connect an appropriate accessory to input
channel #1 or #2. Enter Stopwatch mode and press the Start/Stop key. The Smart
Timer will beep and a “*” will appear on the second line of the LCD. At this time
the accessory will be powered. By blocking and unblocking the beam in the case of
the Laser Switch, or by dropping the steel ball in the case of the Free Fall Adapter,
the elapsed time will be measured. The Smart Timer will resolve 100 microseconds
in the alternate timing mode.

➤ Notes about the Stopwatch Mode:

1. Although it is possible to use older style fences in the alternate timing function to
obtain photogate beam block times, the Smart Timer will provide much higher
accuracy when used with the included fences and the standard timing modes.

2. Two photogates cannot be plugged into the Smart Timer when you are using a
photogate to start and stop the timer. A single photogate can be plugged into channel
#1 or #2 to start and stop the timer. But if two photogates are plugged in, when one
gate is blocked, the other gate immediately is counted as an unblock, and the timer
will display 0.0001 seconds, regardless of the length of time the first photogate is
blocked.

3. You cannot start the timing with the Start/Stop key and end it with a photogate
block or vice versa.

➤ Note:

The stopwatch
function is not a
precision timing
mode and is
therefore most
useful for events
that are longer
than one second.
The accuracy of
the stopwatch is
+/-10
milliseconds.

➤ Hint:

For easier
alignment of the
laser with the
Laser Switch, use
the Test:Gates
mode.

4. If a photogate is plugged in and blocked when you try to use the Start/Stop key as a
stopwatch, the Smart Timer will be timing the photogate and waiting for the
photogate to become unblocked. So when you push the Start/Stop key, the asterisk
disappears and when you push the Start/Stop key again, the asterisk reappears. No
time is displayed until the photogate is unblocked.

Speed Modes

One Gate: In this mode a 1 cm flag passes through the photogate. The Smart Timer
measures the time and calculates the average speed in cm/s.

Collision: In this mode either one or two carts and one or two photogates can be used for
a collision experiment. Once Start/Stop is pressed, the Smart Timer waits for the first
collision and begins timing. The Smart Timer stops timing when two carts have passed
through their respective photogates twice. Timing can always be stopped manually by
pressing Start/Stop and the Smart Timer will display speed(s) based on the information it
has (you will need to press Start/Stop for single cart collisions). The display will present
the results in the following format:

1: xx.x,yy.y
2: xx.x,yy.y

The first number represents the input jack and the following two numbers indicate the
initial speed (xx.x) and final speed (yy.y), respectively.

7

Table 1. Summary of Smart Timer Modes

Type Modes Key Sequence* Timing Diagram** Calculation Algorithm

One Gate

Fence

Two Gates

TimeSpeed

Pendulum

Stop Watch

One Gate (cm/s)

Collision (cm/s)

Pulley (rad/s)

Pulley (rev/s)