PASCO Motion Sensor II CI-6742A User manual

Greeting the Sensors
Waving at the (ultra-sound) motion sensor: PASCO Motion Sensor II CI-6742A
Introduction:
The Motion Sensor II works with a ScienceWorkshop-compatible interface and PASCO data
acquisition software (such as PASCO Capstone) to measure and record motion data. It
produces a series of ultrasonic pulses and detects the sound refecting back from an object in
front of it. The interface measures the times between outgoing pulses and returning
echoes. From these measurements, the data acquisition software determines the position,
velocity, and acceleration of the object.1
Quick Start
1. Connect the Motion Sensor II to your ScienceWork-shop interface and start Capstone
on the computer.
2. Register the sensor with Capstone.
3. Place an object in front of the sensor at least 15 cm away.
4. Click “Record” or press “Start” to begin recording data.
5. Move the object in a straight line directly away from or toward the sensor.
To Aim the Motion Sensor at an Object
1. Set the range switch to short range () or long range () setting.
•Select for measuring a cart on a track.
•Select for measuring most other objects.
2. Arrange the Motion Sensor and object so that the Motion Sensor's transducer faces the
object.
•The object should be at least 15 cm from the transducer.
•If the object will move, it should move directly toward or away from the Motion
Sensor.
•Aim the motion sensor slightly up to avoid detecting the tabletop.
3. Remove objects that may interfere with the measurement. These include objects
between the sensor and target object, either directly in front of the sensor or to the
sides.
To Record Data in Capstone, click Record and the Motion Sensor will begin clicking. If a target
is in range, the target indicator fashes with each click. The data acquisition software should
start collecting and displaying data. Click Stop to stop data collection.
To Display Data without Recording in Capstone:
Click the Recording Mode menu and select Fast Monitor Mode. The Record icon changes to a
Monitor icon. Click Monitor to display live data without recording it.
Sensor Confguration:
To Change the Sample Rate in Capstone, click the up or down button next to the Sample Rate
setting.
The normal range of sampling rates is between 1 Hz and 50 Hz. At the default rate, the
Motion Sensor can measure distance up to 8 m. The maximum distance decreases with
increasing sample rate. At very high sample rates (between 50 Hz and 250 Hz), the maximum
distance is less than 2 m.
Equipment Mounting:
•Mount the Motion Sensor as illustrated ona vertical rod (a) or a horizontal rod (b).
•Integrated clips allow it to be attached to the end of a dynamics track (c).
•A threaded hole in the bottom of the unit (d) is provided for attachment to the PS-2546
Magnetic Bracket (e), the ME-6743 Cart Adapter (f), and other 1/4-20 threaded
mounting devices such as a camera tripod.
1Note: Essential PASCO Capstone tasks are described brieflin this
instruction sheet. For more instructions on using Capstone, see the User’s
Guide or the online help

To protect the Motion Sensor from being hit by an object, use a device such as the SE-7256
Motion Sensor Guard (g) or ME-9806 bracket with a rubber band (h). The Motion Sensor can
“see through” a wire screen or rubber band placed close to the transducer.
Troubleshooting: If the Motion Sensor fails to perform satisfactorily, try these steps:
•Ensure that the target object is no closer than 15 cm.
•Switch the range switch to the other setting.
•Adjust the aim left, right, up, or down. In some cases the Motion Sensor works best
when it is aimed slightly to the side or above the target in order to exclude interfering
objects.
•Improve the target by adding a larger or harder surface to refect ultrasound. A small
object can be a better refector than large object if it has a harder surface.
•Remove interfering objects near the target object or sensor.
•Increase or decrease the sample rate.
Theory ofOperation:
The Motion Sensor uses an electrostatic transducer as both a speaker and a microphone.
When triggered by the interface, the transducer transmits a burst of 16 ultrasonic pluses
with a frequency of about 49 kHz. This burst of pulses can be heard as a single click. The
ultrasonic pulses refect oan object and return to the sensor. The target indicator on the
sensor fashes when transducer detects an echo.
Sound intensity decreases with distance; to compensate, the sensor increases the gain of the
receiver amplier as it waits for the echo. The increased gain allows the sensor to detect an
object up to 8 m away. The lower gain at the beginning of the cycle reduces the circuit's
sensitivity to echoes from false targets.
The interface measures the time between trigger rising edge and the echo rising edge. The
data acquisition software uses this time and the speed of sound to calculate the distance to
the object. To determine velocity, the software uses consecutive position measurements to
calculate the rate of change of position. Similarly, it determines acceleration using
consecutive velocity measurements.
Minimum Range: 15 cm
Maximum Range: 8 m
Transducer Rotation: 360°
Range Settings:
•Short Range: for distance measurement up to 2 m with improved rejection offalse target
signals and air-track noise
•Long Range: for distance measurement up to 8 m
Mounting Options:
•On rod up to 12.7 mm diameter
•Directly to PASCO dynamics tracks
•On table top
Connector: Dual stereo phone plug for ScienceWorkshop-compatible interfaces
Verify the Sensor's Performance and connection to DAQ (data acquisition) software:
1. Connect the Acceleration Sensor to the computer interface with the interface cable
(see Figure 1a) and set up Capstone. Open a Digital Display and select position from
the pop-up menu. Set the range switch on the sensor to long (stick gure icon).
2. Create a digital display of the position reading and begin recording data in continuous
mode
3. wave a hand around and watch the echo indicator and the digital display to get a feel
for the cone of reliable detection
4. take picture of group members miming the extent of the cone
5. change range to short (cart)
6. Wave around again to get a feel for the cone of detection
7. take picture of group members miming the extent of the cone

Greeting the Sensors
Flipping out over accellerometers: PASCO Model CI-6558 Rev A
Introduction:
The Acceleration Sensor is designed to measure accelerations ranging up to 5 times the
earth's gravitational eld with an accuracy of 0.01 g (g = acceleration of gravity, 9.8 m/s
It produces a bipolar output that may vary from +5 g to -5 g, depending on the direction of
acceleration. It is capable of resolving changes in acceleration on the order of 1 milli-g when a
gain of 10 is applied in Capstone
It has two built-in features for conguring it to a particular application:
(1) a tare button, used to set the output of the sensor to 0 regardless of the acceleration being
applied (allows the eect of the earth's gravitational eld to be nulled);
(2) a lter with two settings —"slow" or "fast", setting the frequency response of the
Acceleration Sensor to a range suitable for the application.
For experiments such as measuring the acceleration of elevators, roller coasters, and
automobiles, select the "slow" setting. The slow lter reduces errors due to high frequency
vibrations and noise. For applicationsinvolving mechanical systems, such as cart collision
experiments, select the fast setting.
The Data Studio software will display the output of the Acceleration Sensor in units of m/s2, or
in terms of g.
Very small values of acceleration can be measured by taring the sensor and adding gain in
Data Studio.
Verify the Acceleration Sensor's Performance in the Earth's Gravitational Field:
8. Connect the Acceleration Sensor to the computer interface with the interface cable
(see Figure 1a) and set up Capstone. Open a Digital Display and select Acceleration (g)
from the pop-up menu. Set the lter switch on the sensor to SLOW.
9. Place the sensor fat on a level surface with the arrow indicating direction of sensitivity
parallel to the ground (Figure 3a) and press the tare button.
10. Orient the sensor so the arrow on the label is perpendicular to the ground (see Figure
3b). Monitor Data in Capstone.
11. Observe that Capstone is displaying a value for acceleration of either plus or minus 1g.
12. Rotate the sensor 180° around its major axis so the arrows point in the opposite
direction.
13. Observe that Data Studio now displays 1 g with the opposite sign as observed before.
14. Can you imagine a way to measure the tilt angle of the sensor? (Hint: tilt angle =
arcsin(acceleration in g) ).
Figure 5. Response ofthe Acceleration Sensor to the earth's gravitational feld