How to determine decay time with different color backgrounds


My colleagues and I are testing the decay time of the QTR-MD-04RC Reflectance sensors using an oscilloscope, power supply, and function generator. We want to test the decay time between a white, gray, and black background. Notice in Figure 3 we have two cassettes with the white and gray background, respectively.

Ideally, we want to use the function generator in lieu of the Arduino with a high z mode to simulate putting a charge on the output of the OUT. We’ve powered the device with a power supply and connected to an oscilloscope to measure the delay time. However, we’re seeing a change in the rise time and not the decay time. Do you have any advice or suggestions on what we should do? For example, do we have the pin placement correct, correct oscilloscope settings, etc.

I’ve provided screenshots with captions below (Figures 1-5). Any guidance would be greatly appreciated!

Figure 1: Oscilloscope reading that displays a rise time.

Figure 2: Power Supply and function generator settings.

Figure 3: Full set up (oscilloscope, function generator, power supply, cassettes).

Figure 4: Top view of the connections.

Figure 5: Close up of the selected pin connections.

The connections to your QTR sensor look okay (though I cannot inspect the soldering), but the rest of your pictures are too small for anyone to check the connections or settings in any detail. Instructing you on how to use your measurement equipment is typically beyond the scope of our technical support, but if you can post better pictures, then I can take a quick look and let you know if there is anything obviously wrong.

- Patrick

Thank you Patrick! After many attempts, it was determined that the function generator was the issue. We needed the sensors to discharge, but the generator was bringing the charge up. Thank you for your reply and I apologize for the small pictures.

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I am glad to hear that you figured it out! Thanks for letting us know.

- Patrick