WDSS Troubleshooting

Below are some of the common problems encountered with the WDSS. For the most up-to-date help with the WDSS and Bluetooth communications, visit www.vernier.com/bthelp

My WDSS does not show when I choose Connect Interface.

• Make sure your WDSS is fully charged or has good batteries in it
• Make sure the WDSS is in range for the Bluetooth radio communication. There should not be a metallic barrier between the computer and the WDSS.

The Connection LED turns red when I try to start remote data collection

The WDSS memory is full.

My data seem strange when I am studying a high frequency signal

The best example of aliasing is seen in movies or television where a car wheel appears to be turning backwards. This happens because the camera only looks at the wheel at certain times and it happens to catch the wheel a bit earlier in it's rotation each time around. Think of a pendulum where you "sample" just slightly faster than one period. You'd keep seeing it a bit earlier in it's cycle making it look like it was moving very slowly backwards. If you happened to sample it at an interval exactly the same as its period, it would seem to stand still.

Obviously then, "undersampling" as we call it, can cause some very strange looking data that looks more like an offset or drift than the noise you'd expect. To minimize this problem, system designers use the highest practical sampling rate (not affected by the Logger Pro sample rate that you select) and use filters to prevent noise from ever reaching the sampler. In most cases these techniques reduce the aliased noise component to a point where it's not noticed. There are situations though where the noise is much "louder" than the desired signal and, even though the filter reduces it, enough gets through to affect the data. Toy cars with hard wheels on a rough surface can generate great amounts of acceleration noise that could alias into something that might obscure the phenomenon that you are trying to see. Fans can be another huge source of acceleration noise (vibration).

Bottom line: You will get the best data with smooth quiet running apparatus. Large, soft wheels are better than small hard wheels and heavier vehicles will tend to run quieter as well. The sensors in the WDSS are capable of very precise measurements but some care must be taken to see that noise does not interfere. If you're getting data that doesn't appear to add up look for sources of noise that could be aliasing.