Activities/Measure

About

This Activity draws a picture of the sound heard by the internal microphone or of the signal present on the microphone socket. More specifically it draws a graph of this input versus time, the input is on the vertical axis and time is on the horizontal axis. That is, the laptop functions like a machine called an oscilloscope.

As well as graphing signal as a function of time, Measure can also graph as a function of frequency.

The XO-1 laptop is only capable of mono input, the XO-1.5 and XO-1.75 are capable of stereo input on their microphone socket and can graph two signals at once.

Note: As of Measure Version 37, older versions of Sugar, e.g. 0.84, are no longer supported.

Where to get Measure

http://activities.sugarlabs.org/en-US/sugar/addon/4197/

Using

1. Select secondary toolbar: Allows the Activity's Journal entry to be renamed

2. Select secondary toolbar: Measurement settings

3. Select secondary toolbar: Tuning settings

4. Time base/frequency: Plots the signal vs. time or plots amplitude vs. frequency

5. The time scale: Used to scale the plot

6. Freeze the display: Pause the program

7. Capture sample now: Saves an image of the wave in the Sugar Journal

8. Stop: Exits the Activity

9. Mute: Mute/unmute channel

10. Invert: invert the display

11. Amplitude adjustment: Use these sliders to control the sensitivity

12. Caption: A summary of current settings that are selected

Sensor toolbar

The sensor toolbar - measurement settings

13. Sound: Use this setting with the internal microphone, external microphone and external AC signals

14. Resistance sensor: Use with external resistive type transducers

15. Voltage sensor: Use with external sensors which generate a voltage

16. Sample interval: A log file 'Measure Log' is saved to the journal, it contains one sample per interval

17. Starts/stops saving a log file: 'Measure Log' with measured values as readable text

18. Trigger: Synchronise the sample period to the waveform so that the sample will start on a rising edge or falling edge

There is no 19.

Note: Whenever you switch sensing modes, Measure switches to time-base plotting.

Tuning toolbar

The tuning toolbar - frequency settings

Hint: Adjust the time scale (#5) to increase the spacing between the tuning lines.

20. Instrument: Select instrument to tune.

21. Note entry: Select a note for tuning. (When an Instrument is selected, the notes are restricted to the open notes of that instrument; when no instrument is selected, any of the 88 notes on a piano can be selected.)

22. Frequency entry: The frequency of the target note is displayed. (The user can also enter a frequency to target.)

23. Show/hide tuning mark: A tuning mark displays the target note on the plot.

24. Show/hide harmonics: Harmonic lines are integer multiples of the target frequency.

25. Play a note: Plays a five-second sample of the target note. (Sampling is disabled while the note is playing.)

26. Measured note: An estimate of the note being played is displayed. If the note is slightly flat or sharp, relative to the target, it is displayed in color (red == very flat or sharp; yellow == somewhat flat or sharp).

Note: Whenever you switch to a tuning mode, Measure switches to frequency-base plotting.

Measuring A5 (880 HZ)

Guitar tuning lines

Applying

Let the children experiment with the internal microphone, try singing, whistling, musical instruments, the Tam Tam musical Activity. The Turtle Blocks Activity can generate an audio tone.

The children should learn through guided discovery that:

sound is a pressure wave
the pitch of the sound is determined by the frequency or cycles per second (Hz)
the loudness of a sound is determined by the amplitude
sounds contain multiple frequency components or harmonics
the more pure sounds have less harmonics

Sharing

This Activity does not currently support sharing. However, it is useful to use one XO for measuring and another for generating sounds.

Extending

Measure is able to take input from a wide range of external sensors including switches, photocells, temperature sensors, inductive loops, hall effect sensors, soil probes and many more.

Care should be taken not to exceed the allowable input voltage:

XO-1 -0.5V to 5V
XO-1.5 -6V to +9V
XO-1.75 -6V to +9V

It is a good idea, particularly on the XO-1, to put a resistor of 680 ohms in the phono plug, this increases the allowable input voltage range.

Plotting

You can use save data from measure to the Sugar Journal using the Capture feature described above (16). These data can then be imported into SimpleGraph, where they are displayed.

More ideas

You can find ideas for fun science experiments at Activities/TurtleArt/Using_Turtle_Art_Sensors and http://wiki.laptop.org/go/Measure

Building sensors

There are detailed instructions for building sensors at http://wiki.laptop.org/go/Measure#How_to_build_low_cost_sensors

Adding instruments

You can add new instruments to tune by modifying the instrument dictionary in config.py.

INSTRUMENT_DICT = {
   _('Guitar'): [82.4069, 110, 146.832, 195.998, 246.942, 329.628],
   _('Violin'): [195.998, 293.665, 440, 659.255],
   _('Viola'): [130.813, 195.998, 293.665, 440],
   _('Cello'): [65.4064, 97.9989, 146.832, 220],
   _('Bass'): [41.2034, 55, 73.4162, 97.9989],
   _('Charango'): [329.63, 392, 440, 523.25, 659.26],
   _('Ukulele'): [261.626, 329.628, 391.995, 440],
   _('Sitar'): [174.614, 130.813, 195.998, 65.4064, 391.995, 261.626, 523.251],
   _('Mandolin'): [195.998, 293.665, 440, 659.255],
   _('Recorder'): [391.995]
   }

Reporting problems

Make comments/suggestions on the Talk:Activities/Measure page.

Please file bugs at [1].

To list all open tickets of Measure, see [2].