Vernier Motion Encoder System User Manual
Vernier Motion
Encoder System
(Order Code: VDS-EC)
The Vernier Motion Encoder System
is a Vernier Dynamics System outfitted
for the precise study of dynamics cart motion without the use of ultrasonic motion
detectors. The encoder system 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, a change in position with 1 mm resolution can be
determined, as well as the direction of travel. 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.
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 Motion Encoder System
Motion Encoder Cart with magnetic and hook-and-pile end caps
Motion Encoder Receiver
Plunger Cart with magnetic and hook-and-pile end caps
Mass – 500 g
Combination 1.2 m dynamics track/optics bench with encoder strip
Adjustable leveling feet
Mounting hardware for Dual-Range Force Sensor and accelerometers
Adjustable End Stop
Motion Detector Bracket
*
Patent Pending
*
2 Photogate Brackets
Rod Clamp
Allen wrench 3/32 inch
Collect Data with the Vernier Motion Encoder System
This sensor can be used with the following interfaces to collect data:
Vernier LabQuest
Vernier LabQuest
Vernier LabPro
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.
Essential steps for using the Vernier Motion Encoder System:
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.
®
as a standalone device or with a computer
®
Mini with a computer
®
with a computer
Data-Collection Software
This sensor can be used with an interface and the following data-collection software.
Logger Pro 3 This computer program is used with LabQuest or LabPro.
Version 3.8.6.2 or newer is required.
LabQuest App This program is used when LabQuest is used as a standalone
device. Versions 1.7.1 for the original LabQuest and 2.2.1 for the LabQuest 2,
or newer, are required.
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
Accuracy and Resolution 1 mm
Optimum data-collection rate 15–30 Hz
1.2 m track
2.2 m track
2
Calibration of the Vernier Motion Encoder System
This sensor is equipped with circuitry that supports auto-ID. When used with
LabQuest, LabQuest 2, or LabQuest Mini, the data-collection software identifies the
sensor and configures an experiment appropriately.
No calibration of the Vernier Motion Encoder System is necessary. 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 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 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 Vernier
Motion Encoder Systems to monitor the motion of two encoder carts, so that the
positive direction is the same in both cases.
Because the track strip must be continuous, the Vernier Motion Encoder System
cannot be used with the 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 be reset. The receiver is powered by the
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 this setting is not used, 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: MEC-VDS) 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, 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
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 that
the zero point is initially determined by where on the track 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 software. Place the cart in the
position you want to declare as zero. On LabQuest, tap the meter display 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 popup menu in the Set Up Sensors
dialog for your interface on 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 the Settings for… File menu item
in Logger Pro.
3
4
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.
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 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.
Newer 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.
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.
Adjustable End Stop
The Adjustable End Stop slides into the end of
the track. Adjust the position as desired. Insert
magnets in the End Stop if desired.
Rod Clamp
The Rod Clamp is used to support the track with a
user-supplied ring stand. 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 mass. To attach a
Wireless Dynamics Sensor System (WDSS)
use the hardware supplied with that device.
The hex-head bolts may be attached to any
point along the slots in the cart, but the head
must be inserted in the flare region of the
slots. Tighten the threaded barrels on the
bolts.
5
6
Loading...