Vernier DTS-EC User Manual

Vernier Dynamics Cart and Track
System with
Motion Encoder

(Order Code DTS-EC)

The Dynamics Cart and Track System
with Motion Encoder is outfitted for the
precise study of dynamics cart motion without the use of ultrasonic motion detectors.
Instead of a traditional Motion Detector (order code MD-BTD), the system makes
use of a novel Motion Encoder System. The encoder consists of several parts:

 A track with an encoder strip along the length of the track
 A dynamics cart with an optical encoder and infrared (IR) transmitter
 A receiver, attached to the end of a track

The encoder strip consists of alternating black and white bars with a 4 mm period,
allowing the optical sensor to detect the passage of the bars as the cart moves. With
two sensors appropriately placed on the underside of the cart, a change in position
with 1 mm resolution can be determined, as well as the direction of travel of the cart.
A narrow infrared beam transmits motion data to a receiver.

No alignments or adjustments are necessary, as the receiver attaches firmly to the
track, and the cart rides in slots on the track. The IR beam is not disturbed by
reflections from nearby objects.

The system is designed for use in physics and physical science courses for motion
and energy experiments. An optional Optics Expansion Kit (order code OEK)
converts the track to an optics bench. A 2.2 m track is also available.

Some typical experiments done with the system include

 Motion under zero acceleration
 Motion under constant acceleration with the ramp inclined
 Inelastic collisions using the included hook-and-pile tabs
 Elastic collisions using the included magnetic bumpers

Parts Included with the Vernier Dynamics Cart and Track System
with Motion Encoder

 Motion Encoder Cart with 2 magnetic and 2 plain collision tabs
 Motion Encoder Receiver
 Plunger Cart with 2 magnetic and 4 plain collision tabs
 Cart Masses (4) – 125 g
 Combination 1.2 m Dynamics Track/Optics Bench with encoder strip
 Adjustable Leveling Feet

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 Mounting hardware for Dual-Range Force Sensor and Low-g Accelerometer

(2 large bolts and 4 small bolts)

 Adjustable End Stop
 Motion Detector Bracket
 Motion Detector Reflector Flag with 2 magnetic collision tabs
 2 Photogate Brackets
 Rod Clamp
 Allen wrench 3/32 inch
 Ultra Pulley
 Pulley Bracket

Compatible Software and Interfaces

See www.vernier.com/dts-ec for a list of interfaces and software compatible with the
Vernier Dynamics Cart and Track System with Motion Encoder.

WARNING: The Motion Encoder Receiver is not compatible with the Texas
Instruments TI-Nspire Lab Cradle. Connecting the Receiver to the Lab Cradle will
render the Cradle inoperative, requiring repair by Texas Instruments.

Collect Data with the Vernier Dynamics Cart and Track System
with Motion Encoder

1. Attach the receiver to the end of the track, matching the encoder strip on the track
to the markings on the receiver.

2. Place the track on a level surface.

3. Insert two AAA batteries (not included) into the encoder cart.

4. Connect the receiver to an interface such as a LabQuest 2. If using a computer,
connect the interface to your computer and launch Logger Pro.

5. Turn on the cart by pressing the power button. It will glow blue when the cart is
on.

6. Place the cart on the track, wheels in grooves, with the blue light facing the
receiver.

7. Begin data collection, and let the cart roll.

NOTE: Vernier products are designed for educational use. Our products are not
designed nor are they recommended for any industrial, medical, or commercial
process such as life support, patient diagnosis, control of a manufacturing process, or
industrial testing of any kind.

Specifications

Measurement Range
1 m range
2 m range

1.2 m track

2.2 m track
Accuracy and Resolution 1 mm
Optimum data-collection rate 15–30 Hz

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Calibration of the Motion Encoder System

Calibration of the Motion Encoder System is not necessary nor is it possible. The
printed bars on the track determine the scale, and the cart encoder counts the passage
of the bars. Available units are meters and feet, selectable in the software.

In contrast, it is possible and desirable to zero the encoder. Unlike an ultrasonic
motion detector, there is no way for the system to have an unchanging reference
position; it can only count bars from the point at which the cart is placed on the
track. As a result, you may want to move the cart to the receiver end of the track and
zero the reading in the software.

The positive direction can be reversed so that readings increase as the cart moves
toward the receiver. A reversed coordinate system is helpful when using two Motion
Encoder Systems to monitor the motion of two encoder carts, so that the positive
direction is the same in both cases.

Because the encoder strip must be continuous, the Motion Encoder System cannot be
used with a Track-to-Track Coupler.

Power

The Motion Encoder Cart requires two AAA batteries. Either NiMH rechargeable
batteries or alkaline disposable batteries can be used. Turn on the cart by pressing the
clear power button on the cart endcap. It will glow blue when power is on. Press
again to turn off. The cart will turn itself off after 20 minutes of inactivity. Any
motion on the track will cause the timer to reset. The receiver is powered by the
data-collection interface.

Battery life depends on use and the range setting. Low battery level may cause
erratic detection of the cart motion, including incorrect velocity signs. Replace the
batteries if this is seen.

Range Setting of the Motion Encoder Cart

The IR transmitter on the cart has two power levels available. The default 1 m
setting conserves battery power. If the cart is used on a 2.2 m track, set the cart to the
higher 2 m power level. If the high-power setting is not used on a 2.2 m track, the
receiver will not reliably sense the position of the cart at the far end of the track. The
switch is located inside the battery compartment.

Use of Two Vernier Motion Encoder Systems on the Same Track

Some experiments require measuring the motion of two carts. This can be done by
purchasing the Motion Encoder Cart and Receiver (order code DTS-MEC) to add a
second encoder cart, receiver, and strip to your Vernier Motion Encoder System. A
Motion Encoder Receiver is placed at either end of the track, and two Motion
Encoder Carts are used on the track, each with its transmitter facing the unobstructed
receiver. A second encoder strip must be applied to the track, resulting in one on
either side of the center slot.

Consider reversing the direction of one receiver so that the same direction is positive
for each system. Put the carts together, and zero both systems. This will put the carts

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on the same coordinate system; if they move together in contact, their position
readings will be the same.

Use of Multiple Vernier Motion Encoder Systems
in the Same Room

Because of the narrow IR beam used for signaling between the cart and receiver,
interference should be rare. However, if one apparatus is apparently interfering with
another, the problem can be resolved by repositioning one of the tracks.

All Motion Encoder Carts are interchangeable; that is, there is no matching of cart to
receiver.

Data-Collection Notes for the Motion Encoder System

 The optical motion encoder can only make relative position measurements, so the

zero point is initially determined by the location on the track that the cart is first
placed when the power is on. If you want zero to be near the receiver, initially
place the cart next to the receiver. This behavior is very different from the
ultrasonic Motion Detector, which by default uses a fixed origin near the detector.

 The motion encoder is nearly immune to interference, but it cannot work if the IR

beam between the cart and receiver is blocked. Keep your hand away from this
region.

 Since the zero position (origin) of the encoder depends on where the cart is placed

initially, it is often useful to zero the encoder in the software. Place the cart in the
position that you want to declare as zero. On LabQuest, tap the Meter Screen to
access the zero command. In Logger Pro, use the toolbar button.

 It can also be useful to reverse the direction of the coordinate system, so that

values increase as the cart moves toward the receiver. Do this from the Meter
Screen on LabQuest, or by using the Sensor menu in the Set Up Sensors dialog
box for your interface in Logger Pro.

 High data-collection rates are not useful for the motion encoder. Rates above

30 Hz will produce noisy velocity and acceleration graphs because of few counts
during each time period.

 Just like the ultrasonic Motion Detector, it can be useful to adjust the number of

points used to calculate derivatives for velocity and acceleration graphs. Higher
values create quieter graphs, while lower values result in more temporal detail.
Adjust this value in LabQuest preferences or in Settings For… from the File menu
in Logger Pro.

Photogate Bracket

Photogate Brackets are attached to the side of the track.
With the nut loosely on the T-handled bolt, slide the nut
into the side channel of the track. Attach the photogate
using the supplied wing bolt in the long slot. Adjust the
gate height so the beam intercepts the desired portion of
the target.

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Motion Detector Bracket

Although we expect that the motion encoder will be used most often to record
motion data, it is also possible to use the Dynamics Cart and Track System with an
ultrasonic Motion Detector.

Any Vernier Motion Detector with a hinged head can be attached to the supplied
Motion Detector Bracket. The Motion Detector Bracket has a pin to locate the
Motion Detector on the bracket. There is
a knob, nut, and bolt to attach the
bracket to the track underside, and a
threaded hole at the end near the pin. To
assemble, place the Motion Detector
with the back end over the pin of the
bracket. Insert the screw through the slot
into the threaded insert on the detector
with the hinge toward the track, and tighten. Insert the bracket into the slot in the
underside of the track as shown in the photo. When the Motion Detector is not
attached to the bracket, its mounting screw can be stored in the threaded hole near
the pin.

Most Vernier Motion Detectors (green or black case with
adjustable sensitivity) can be placed so that the sensor is 15 cm
from the end of the track. The carts can then be detected
properly all the way to the end. The track mode is appropriate
for the dynamics system. Older Motion Detectors that lack a range switch can still be
used, but the carts must remain beyond the 45 cm minimum working distance of
these older sensors.

Motion Detector Reflector Flag

Some users prefer to enhance the
reflectivity of the cart when using
an ultrasonic Motion Detector. Use
of the Motion Detector Reflector
Flag makes the position of the
detector less critical, but its use is
optional.

The Motion Detector Reflector Flag attaches to the dark gray end of a cart. Insert
magnetic collision tabs and snap the flag against the end of the cart, with the metal
inserts against the magnet tabs. Place the cart on the track with the flag toward the
Motion Detector.

Adjustable Leveling Feet

The Adjustable Leveling Feet slide into the
end of the track, with the nut in the center
slot of the track underside. Adjust the
height as desired. Install the feet before
attaching the Motion Detector Bracket.

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Adjustable End Stop

The Adjustable End Stop slides into the top slot from
the end of the track. Adjust the position as desired.
Insert magnets in the End Stop if desired. The End
Stop cannot be used at the same end as a Motion
Detector or Motion Encoder Receiver.

Rod Clamp

The Rod Clamp is used to support the track with a user­supplied ring stand. A 12 mm rod is the maximum size
accommodated. Insert the Rod Clamp nut into the side of
the track. Adjust the height as desired.

Mounting Hardware

The supplied mounting hardware is used to attach
devices to the cart, such as a force sensor,
accelerometer, or Wireless Dynamics Sensor System.

Additional Mass

The four 125 g masses are used to change the mass of
the cart for dynamics experiments. The cart mass is
nominally 250 g, but additions such as magnets, hook­and-pile tabs, sensors, and the encoder system will
increase the total mass. As a result, it is best to weigh
the cart as used when the mass is important.

The four masses can be used one at a time or in
combination on either cart. The mass trays on the sides
allow the addition of masses without removing sensors.
It is not necessary to keep the carts balanced with the
same mass on each side.

Pulley Bracket and Pulley

The Pulley Bracket and Pulley can be attached
to the end of the track to create a half-Atwood
machine using user-supplied masses and
string. It can be assembled with or without a
Photogate for motion measurement.

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Insert the oblong nut into the bottom slot of the track and tighten. To attach the
pulley without a Photogate, use the short bolt to attach the pulley. Adjust the height
of the pulley as needed to keep the string level. To include a Photogate, slide the
plastic photogate mount over the vertical portion of the Pulley Bracket, with the
open slot outward and upward. Insert the Vernier Photogate into the mount, and pass
the long bolt through the bracket, and Photogate, capturing the threads of the bolt
with the Pulley.

Collision Tabs

The Vernier dynamics carts are supplied with
magnets and hook-and-pile tabs. These parts
are attached using removable Collision Tabs.
Since the magnets may interfere with certain
experiments using force sensors on the carts,
only install the magnets if you need them.

The magnets are useful in studying collisions with the magnets positioned so that
they are the same polarity on both sides and on both carts. This way the carts will
repel one another, and you can arrange a collision in which the carts never actually
touch. The collision will be very nearly elastic, unlike a collision using a spring or
any kind of contact.

The removable Collision Tabs have two sides. One is marked N, and the other is
plain. The plain side is for use with hook-and-pile material on tabs without magnets.

The Collision Tabs can be inserted either way, exposing or concealing any hook­and-pile material. To quickly perform an experiment without magnets, remove the
Collision Tabs.

The Adjustable End Stop will hold magnets as well. Note that only low-speed
collisions with the End Stop will keep the cart on the track.

To install magnets on the Adjustable End Stop, use the following procedure:

1. Remove the teardrop from the cart end or the End Stop.

2. Insert the silver magnet (supplied with the cart) into the teardrop, oriented so that
the outside of the teardrop will attract the south-pointing end of a compass needle.

3. Insert a foam plug (supplied with the cart) into the teardrop.

4. Reinsert the tear drop into the cart end or the End Stop, and fasten the screw.

If you like, test by holding the compass near the cart or End Stop, in the same
position as an approaching cart, and verify that the south-pointing end of the
compass is attracted to the cart.

The magnets can be removed at any time by reversing this process. Store the
magnets away from computers.

To study totally inelastic collisions, place hook-and-pile tabs on the Collision Tabs
without magnets. Looking at the end of the cart, place a hook pad on the
left-hand plug, and a pile tab on the right-hand side. Center the pad on the round part
of the Collision Tab. This way any cart with hook-and-pile tabs will stick to any

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other. Hook-and-pile equipped carts will stick together, creating a totally inelastic
collision.

Plunger Cart

One cart includes a spring-loaded plunger for collisions. To use the plunger,
simultaneously press the horizontal button above the plunger and press the plunger
in until it locks. To release, press on the pin from the top of the cart. The plunger
force can be adjusted. To adjust the plunger release force, rotate the plunger while it
is extended. An uncalibrated scale is visible on the underside of the cart. Use this
scale to return to a previous setting.

The Plunger Cart is capable of superelastic collisions. To enable this mode, use a
small screwdriver to unlock the dark gray plastic plug below the main plunger.
Depress the plug using the screwdriver and rotate one-half turn counterclockwise to
unlock. The plunger will extend about 2 mm.

Lock the plunger as before to prepare for a superelastic collision. In a collision, the
plug will strike first and trigger the release of the plunger.

To disable superelastic collision mode, use a small screwdriver to depress and rotate
the plug one-half turn clockwise. It will lock in the flush position.

The plunger cart has a nominal mass of 250 g. Adding accessories such as sensors or
magnets will change the mass.

Use of Additional Accessories and Sensors

The following examples show various sensors attached to a Vernier dynamics cart.
Sensors are not included with the Dynamics Cart and Track System with Motion
Encoder.

Attach the Dual-Range Force Sensor (DFS)

1. Place the sensor over the two silver pins as
shown on the cart top sheet. Older force
sensors may require moving the pins to the
wide spacing option.

2. Use the large bolt to secure the sensor to the
cart as shown.

3. Configure the force sensor as needed with a
hook, bumper, or magnet.

Attach the Low-g Accelerometer (LGA)

The Accelerometer has mounting holes on the
cart top sheet.

1. To attach an accelerometer, place the sensor
over the mounting holes as shown on the
cart top sheet.

2. Use two small mounting bolts to secure the
sensor as shown.

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Attach the DFS and LGA in Combination

The DFS (Dual-Range Force Sensor) and LGA (Low-g Accelerometer) can be used
simultaneously using the same procedures.

Wireless Dynamics Sensor System

To attach a Wireless Dynamics Sensor System (WDSS), remove and store the two
silver pins for the Dual-Range Force Sensor. Place the WDSS on the top surface of
the cart, and use the large mounting bolt to secure the sensor to the cart.

General Tips for the Vernier Dynamics Cart and Track System

 Do not install the magnets unless you know you want to use them. They will

interfere if you perform an experiment with a force sensor riding on the cart, since
the force sensor will then not read the total force acting on the cart.

 The magnets are designed for fairly gentle collisions. If the cart is moving too

quickly, the magnetic forces may cause the cart to jump off the track to the side. If
this happens, use a lower initial velocity for the cart.

 Keep the track clean; if it is dirty the carts will not roll smoothly.
 Use lower speeds and lower inclines than you might initially choose; the physics

is the same and students will have more time to observe what is happening.

 Attach the track feet, sliding at least one in about 30 cm before inserting the

Motion Detector Bracket.

 Study the Motion Detector Bracket photo carefully and note that the bracket is

attached to the underside of the track. A common error is to attach the bracket to
the top slot on the track.

Suggested Experiments

The Vernier Motion Encoder System can be used wherever a Motion Detector could
have been used with a cart and track. The encoder depends on the presence of the
track, so that only cart and track experiments can be performed.

Measure Cart Acceleration

The basic motion of a cart on a ramp can be studied. For example, perform
Experiment 3 from Physics with Vernier, “Cart on a Ramp.” Or, repeat Galileo’s
experiment of determining g using an object and a ramp. This is Experiment 4,
“Determining g on an Incline,” from Physics with Vernier.

Newton’s Second Law

Use a force sensor on the encoder cart to record both applied force and acceleration.
The two will be proportional.

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Or, set up a half-Atwood machine with a hanging mass and a pulley at the track end
opposite the receiver. Measure the acceleration of the encoder cart as a function of
the hanging mass.

Measure Fan Cart Acceleration

Add an Encoder Fan Cart (order code CART-FEC) to observe the motion of a cart
under constant thrust.

Measure Cart Acceleration with Friction

Add a Friction Pad (order code DTS-PAD) to the encoder cart and observe the
motion of the cart with varying frictional forces.

Momentum-Impulse

Add a force sensor and a Bumper-Launcher Kit (order code BLK) to observe the
relationship between momentum and impulse. Find the impulse by integrating under
a force vs. time graph.

Conservation of Energy

Use two Vernier Motion Encoder Systems to observe a change in energy due to a
collision between two carts.

Conservation of Momentum

Use two Vernier Motion Encoder Systems to observe a change in momentum due to
a collision between two carts. Try different kinds of collision: elastic, inelastic,
totally inelastic.

Products Related to the Vernier Dynamics Cart and Track
System with Motion Encoder

Vernier Dynamics Cart and Track System (order code DTS)

Vernier Dynamics System is a low-friction 1.2 m track and optics bench
combination designed for kinematics, dynamics, and optics experiments. It includes
two carts. The hardware does not include the Motion Encoder Cart and Receiver.

Vernier Dynamics Cart and Track System with Long Track (order code DTS­LONG)

The long version of the Vernier Dynamics System includes a 2.2 m track instead of
the 1.2 standard track.

Track (order code TRACK)

The Combination 1.2 m Track/Optics Bench comes with the Encoder System Strip
installed.

Replacement Parts

Motion Encoder Receiver (order code MEC-BTD)

The receiver attaches to the end of the track and connects to an interface, such as a
LabQuest 2.

Motion Encoder Cart (order code CART-MEC)

This is the complete Motion Encoder Cart, with no assembly required.

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Motion Encoder Long Track Strip (order code METS-LONG)

The strip can be attached to an existing track without an encoder strip, or it can be
attached as a second strip for use with two encoder systems. For 1.2 and 2.2 m
tracks.

Motion Encoder Transmitter Parts (order code MECT)

The transmitter assembly is used to upgrade an existing cart to a Motion Encoder
Cart.

Motion Encoder Cart and Receiver (order code DTS-MEC)

This kit includes a Motion Encoder Cart, a Motion Encoder Receiver, and a Motion
Encoder Track Strip. Add it to a Dynamics Cart and Track System with Motion
Encoder to track the motion of two carts simultaneously.

Ultra Pulley (order code SPA)

The pulley can be attached to the end of a track using the Pulley
Bracket to make a half-Atwood machine.

Pulley Bracket (order code B-SPA)

The pulley bracket allows easy attachment of an Ultra
Pulley to the end of a Vernier track.

Suggested Accessories

Bumper Launcher Kit (order code BLK)

The Bumper Launcher kit includes accessories to integrate the Dual-Range Force
Sensor (DFS-BTA) with the Vernier Dynamics System or Vernier Motion Encoder
System, allowing for many interesting experiments in momentum-impulse study.

Cart Picket Fence (order code PF-CART)

The Cart Picket Fence is a clear plastic sheet printed with black bars for use with a
photogate. Use this to measure precise speed and acceleration.

Dual-Range Force Sensor (order code DFS-BTA)

The Dual-Range Force Sensor measures pushes and pulls up to 50 N.

Wireless Dynamics Sensor System (order code WDSS)

The WDSS is a wireless force sensor and accelerometer.

DTS Cart Friction Pad (order code DTS-PAD)

The DTS Cart Friction Pad attaches to the cart end using the collision tab slots. It
adds an adjustable pad that rubs on the track, adding a controlled amount of friction
to the cart motion. Use it to study frictional forces.

Encoder Fan Cart (order code CART-FEC)

The three-speed Encoder Fan Cart is a large fan on a light-weight cart. It offers
students the ability to perform kinematics and dynamics experiments with constant
acceleration, variable mass, variable thrust, and variable thrust angle. The cart
includes a Motion Encoder Transmitter.

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Optics Expansion Kit (order code OEK)

The Vernier-Optics Expansion Kit extends the
Vernier Dynamics System or Vernier Motion
Encoder System for use in optics experiments.

Color Mixer (order code CM-OEK)

The Vernier Color Mixer Kit consists of a three­color LED illuminator with power supply, a
lens, and a double-sided screen.
Experiments in additive and subtractive
color mixing can be easily and conveniently
carried out using this kit. The intensity of
the red, blue and green LEDs can be
smoothly controlled from the light source.

Diffraction Apparatus (order code DAK)

Use the Diffraction Apparatus to map light intensity versus position for many-slit
geometries.

Warranty

Vernier warrants this product to be free from defects in materials and workmanship
for a period of five years from the date of shipment to the customer. This warranty
does not cover damage to the product caused by abuse or improper use.

Vernier Software & Technology

13979 S.W. Millikan Way  Beaverton, OR 97005-2886

Toll Free [phone]  [phone]  FAX [phone]

[e-mail]  www.vernier.com

Revised 1/5/2016
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