Vernier Software and Technology
Vernier Software & Technology
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How fast does the DCU respond to data?

The Digital Control Unit, order code DCU-BTD, $61 will attempt to collect data at the same rate as the experiment sampling rate. However, it is possible to sample faster than the DCU can respond to an event that should trigger a response.

We conducted several tests using a square wave signal generated at different frequencies and triggering a DCU line based on the voltage from the generator being greater than 0V. The maximum sampling rate that reliably detected and responded to a signal was (approximately) 15 samples per second.

You will want to consider this response time (approximately 0.067 seconds) when designing an activity. For example, one of our engineering extensions has you turn on an LED by blinking. You attach an EKG sensor across the muscles that contract to cause you to blink. This signal can be used to turn on an LED. However, if you blink too fast, you can miss the signal altogether.

Here are some other factors to consider when designing your project:
Is the data source you are triggering off of a single pulse or a periodically repeating stimulus?
If repeating, what is its frequency?
What is your sampling rate (in comparison to the frequency of the data source)?
Is your trigger value at the top of the cycle or a mid-point?

TIL 2101: Digital Control Unit (DCU) Troubleshooting and FAQs

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