Data logger, oscilloscope, signal generator and more!

DrDAQ is a versatile instrument that connects to the USB port of any PC. Using the supplied PicoScope software it can be used as an oscilloscope, spectrum analyzer and signal generator.

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Predicting the motion of a falling card


Educational data loggerThis experiment demonstrates how DrDAQ can be used to investigate how height effects the velocity of a free falling object. This experiment is very simple, and with PicoScope enables the data to be collected rapidly.

The experiment aims to identify and prove existing theories on speed and distance.

Equipment required

  • A PC with PicoScope installed
  • DrDAQ PC based data logger
  • A Bench timer light gate, we used one from Technology Supplies Ltd (product LA30-660):
    Technology Supplies Ltd.
    Phoenix House
    Tern Hill
    Market Drayton
    Tel. 01630 637300.
  • A stand or clamp to hold the light gate.
  • Suitable leads and connectors.

Experiment setup

The idea is to drop a card of known length through the light gate and calculate the speed from the waveform collected in PicoScope.


The card needs to be black so that the signal recorded in PicoScope is sharp due to the light beam being interrupted cleanly. It is also necessary to fix two blobs of Blu-Tack to the card to give it some ballast in order for the card to fall straight.

set up

The output from the Lascells light gate is fed directly into the voltage input and ground of the DrDAQ, from within PicoScope it is immediately possible to see how blocking the light gate effects the voltage levels.

Carrying out the experiment

PicoScope is set up to trigger upon the change in voltage from the light gate, 1000 mV. A pre-trigger is added to show the effect the card has on the light gate in better detail.



The velocity of the card as it passes through the light gate can be calculated by dividing the distance over the time. The distance is a constant, i.e. the card length does not change, however the speed for it to pass through the light gate will depend on the height. The following equation is used:


Where the length is a constant (10 cm) and the time will vary, depending on the time taken for the card to pass through the light gate.


Height Time Velocity
10 cm 60.05 ms 1.6653 m/s
15 cm 49.99 ms 2.0003 m/s
20 cm 45.38 ms 2.2036 m/s
25 cm 41.44 ms 2.4134m/s
30cm 39.13 ms 2.555 6m/s
35 cm 37.18 ms 2.689 5m/s
40 cm 36.1 4ms 2.7671m/s

If this is plotted on a graph the relationship can be seen quite clearly:


Discussion of results

This experiment clearly shows the relationship between acceleration and height fallen. It also demonstrates that the higher the card falls from the greater the final velocity when it passes through the light gate. From the graph it is possible to predict the maximum speed that the card is likely to fall at from the curve of the graph.


  • The kit (2408B) is of obvious quality, easy to setup and calibrate and the free to download software has a reasonable learning curve. Superb kit, superb support, what more can I say.

    Rop Honnor
  • I have been using my 4224 PicoScope for years. I travel abroad so this has been ideal due to its physical size. Storage of waveforms on my Laptop is very easy allowing me to quickly email waveforms to my Colleagues.

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  • PicoLog TC-08: This is a very nice unit that works consistently and reliably.

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  • Perfect Partner for Development of Encoder controlled Stepper Motor Actuators. Since the included software is really stable, this type of device is a great tool for great tasks!

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  • So simple to use & beats any other I have ever used hands down.

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  • Rather than webcam our benchtop scope screen, it was suggested we use a PicoScope to share waveforms via screen share.

    We were a bit hesitant at first … but it worked flawlessly, and everybody is now out shopping for PicoScopes!

    T Lövskog • SVP of Innovation at Additude AB
  • Great functionality in a compact size. I really like moving the mouse pointer to a position and having the Time and Voltage display the values at that point. Calibration equipment is a breeze with that feature.

    Don Horein

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