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Motion Detector Troubleshooting and FAQs

Motion Detector, order code MD-BTD, $79
Specifications and User Guide

There are several Motion Detector models:
-Motion Detector, order code MD-BTD, $79 - green plastic, one LED on the right below the gold screen, track mode switch inside pivoting head (Began shipping 1/2005)
-Motion Detector 1 (MDO-BTD, discontinued) - blue plastic, two LEDs below and to the left/right of the gold screen
-Ultrasonic Motion Detector for ULI (MD-ULI-O, discontinued) - blue plastic, no pivoting head, non-detachable cord ending in clear telephone connector, one red LED below the gold screen
Note For use with LabQuest, the CBL Adapter for ULI Motion Detector, order code CBL-RJ11, \Contact Us is needed.
-CBL Motion Detector (MD-CBL-O, discontinued) - blue plastic, no pivoting head, non-detachable cord ending in white BTD connector, one red LED below the gold screen
-Go!Motion, order code GO-MOT, $119 is functionally interchangeable with the Motion Detector 2. It connects directly to a computer via USB cable. For use with LabQuest, the Digital Sensor Cable, order code MDC-BTD, $5 is needed. For use with calculators, four AA batteries are required.

In addition, there are two models from Texas Instruments:
-CBR 2, order code CBR2, $99 - white and gray plastic, with mode switch inside pivoting head
The CBR2 is functionally identical to the Go!Motion. For use with calculators, four AA batteries are required unless a CBL2 interface is also used.
-CBR - Dark gray plastic
The sensor of the CBR is functionally identical to that in the original Motion Detector.

TIL 3750: How old is my Motion Detector 2?


- Test 1: When you start data collection, do you hear a clicking from the Motion Detector? If not, the sensor may be defective. Sometimes the switch on the inside of the Motion Detector gets stuck between the two positions. Try vigorously flipping the switch back and forth.
- Test 2: If the Motion Detector is not working, the cable could be malfunctioning. Try a cable from a working unit.
- Test 3: To test accuracy, find a wall with no desks, chairs, doors, or other obstructions within a 2 m field. Hold the Motion Detector in your hand, 0.5 m from the wall with the gold disc pointing directly at the wall. Do you get the expected 0.5 m reading? Back off to 1.0 m. Do you get 1.0 m? Back farther off to 1.5 m. Do you get 1.5 m?
- Test 4: Motion Detectors use ultrasound to measure position. Other sources of ultrasound may be interfering with the signal. Those sources include air tracks, CRT computer monitors, fluorescent lights, and power distribution panels. Identifying these sources can be challenging. You may have to resort to moving the Motion Detector away from interfering equipment. In the case of noisy fluorescent lights, turn them off (but we rarely see this problem).

If the Motion Detector itself is not functioning, it is rarely something that can be fixed. Contact Vernier Technical Support at 888-VERNIER (888-837-6437) or to learn what options are available.

- Tip 1: The optimum collection rate is 20 pts/second.
- Tip 2: Clear all objects within the 30 degree cone.
- Tip 3: If you are monitoring the motion of objects on a table or track, tilt the head up slightly.
- Tip 4: Use the Cart-on-track mode switch when using a cart on track. Use Normal (Person/Ball) mode for all other applications. It does no harm to try the other mode.
- Tip 5: Increase the target's area (e.g. tape an index card to the object such that the ultrasound will detect the flat surface of the card).
- Tip 6: Noisy velocity data: increase the number of points used for derivative calculations. See TIL 2331: How do I adjust the number of points used in derivative calculations?
- Tip 7: The maximum sample rate that you can use for the motion detector is 50 Hz, which equates to a sample interval of 0.02 seconds. We do not recommend that setting as it tends to produce noisy data.
- Tip 8: Sometimes the switch on the inside of the Motion Detector gets stuck between the two positions. Try vigorously flipping the switch back and forth.


TIL 5: Why am I getting Motion Detector readings that are noisy or max out at a certain distance?
TIL 2968: Why won't my Motion Detector (or other digital sensor) plug into the channels of my LabQuest 2?
TIL 459: Why don't I get a freefall acceleration value of 9.8 m/s^2 when using a motion detector?
TIL 1011: How does Logger Pro calculate velocity and acceleration from Motion Detector data?
TIL 2698: Why does my data table have holes (empty cells) in it?
TIL 1001: How do you create new match files for MacMotion or Motion?
TIL 2961: How does a Vernier Motion Detector work (electrically)?
TIL 1938: Should I use a photogate or a Motion Detector?
TIL 410: Can you create new match files for Logger Pro?
TIL 2053: How do I improve the results from a Motion Detector with an air track?
TIL 1036: Will your Motion Detector show the speed of a (car, baseball, racquetball)?
TIL 2120: How can I collect data from a photogate and a motion detector data at the same time in Logger Pro?
TIL 2668: Can I do Graph Matching with my Motion Detectors and TI calculators?
TIL 2426: How do I attach the Motion Detector bracket to the Vernier track?
TIL 3384: How do I use two motion detectors or two motion encoders at once to study collisions?

TIL 2655: A mass fell into my Motion Detector and dented the screen. Can the gold mesh screen be repaired?
TIL 1205: My Motion Detector is not collecting data with DataMate and LabPro.
TIL 1914: My motion detector still reads 0.004 m after zeroing.

TIL 649: How do I calibrate a MPLI Motion Detector?
TIL 2972: Is there a way to calibrate the Motion Detector?

TIL 405: Can I use a PASCO motion detector with the LabQuest, LabPro, CBL, or ULI interfaces?
TIL 2996: Which motion detector should I buy? What are the differences between them?
TIL 3862: How do I collect collision data using an Motion Encoder and a Photogate
TIL 3269: Which Motion Detector model do I have?

- Order code: MD-BTD
- Ultrasound frequency: 50 kHz
- Resolution: 1 mm
- Accuracy: 2 mm
- Range: MD-BTD - 0.15 m to 6 m
MDO-BTD - 0.5 m to 6 m
- Speed of ultrasound used to calculate distance: 343 m/s *
- Power: 51 mA while running

*Adjusting the "temperature" setting in Logger Pro changes this value. Speed increases with temperature. We apply a linear correction such that a 1°C change of temperature is equal to 60 cm/s change of speed of sound. The Go! Motion is more sophisticated because it only has a built-in temperature sensor and applies the correction automatically.

- Air temperature corrections are possible only in Logger Pro and Logger Lite in the Sensors dialog.

- Motion Detector Clamp, order code MD-CLAMP, $10, order separately
- Digital Sensor Cable, order code MDC-BTD, $5, shipped with sensor
- Cable Motion Detector to MPLI, order code M-MDC, \Contact Us
- Cable Motion Detector to ULI, order code ULI-MDC, $5
- Motion Detector Bracket, order code MDB-VDS, $11
- Digital Extension Cable, order code EXT-BTD, $12, 2 m in length

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