Talk:Measure

quote

It is said "Give the child a hammer, and the world are his nails".

I need the source for this, I remember hearing it somewhere.--Arjs 12:11, 20 July 2007 (EDT)

line voltage

Never minding the fact that all round (non-USB) ports should tolerate line voltage, how might one make a safe connection? This is useful for showing line frequency and for showing the waveform. Waveforms from UPSes might be particularly interesting. Not being an EE, I can think of a few ideas: transformer, capacitor, resistor. Each of those can be done nicely, with proper electronic parts, or crudely with makeshift parts. 24.110.144.116 00:42, 1 August 2007 (EDT)

Measuring voltages outside 0.3V - 1.9V would require an external probe, the development of which is also in the pipeline.--Arjs 02:37, 15 August 2007 (EDT)

What about the reverse?

Measure turns the audio input into a generic input over a certain voltage range with essentially 0 current. Would it be possible to do the same for the audio output? This could run simple robotics, or allow switching between sensors. Obviously it would NOT be usable as a DC power source, just for switching transistors. Homunq 20:38, 7 August 2007 (EDT)

I have been thinking about that too. It would be interesting if I am able to achieve that. One of the other things that I have been thinking about is a simple generic USB based I/O interface. USB to Parallel chips aren't that expensive too...--Arjs 02:35, 15 August 2007 (EDT)

See Electrical output for further discussion of this and related possibilities...

Im guessing that it would be better to manage the USB ports, because the XO has three of this inputs/outputs, also there are thousands of electronics applications especially designed to USB user:RafaelOrtiz

The USBs although more versatile and flexible , would require us to mostly look at more and more external hardware. --Arjs 08:12, 17 September 2007 (EDT)

agree with, this is a long term shot.RafaelOrtiz

Maximum frequencies

hi Arjs where can i find the specs of measure..i.e maximum frequencies and stuff..?

The maximum sampling rate of the Ad188 sound chip is 48khz , which is the sampling rate I am using. I would say that maximum frequency would be about - 15Khz (slightly less than Fs/2). --Arjs 02:19, 15 August 2007 (EDT)

User feedback

• When the activity first starts, it is taking audio as input. But talking, clapping, etc, may or may not create any visible change in the display. It might be nice if the default settings yielded some clean response to vocal input. To provide a positive very-first experience. Perhaps just show volume? If you can't whistle, it's not clear you can easily play with it. Build 581. MitchellNCharity 18:41, 15 September 2007 (EDT)

  (Moved from User talk:MitchellNCharity): Thanks for your feedback. Voice is hard to characterize (and hence display something concrete) - as it also contains harmonics and there is ambient noise etc. A whistle is relatively much cleaner source of frequency. However I do appreciate your idea and am trying to think how can I prevent a more intuitive first experience...please feel free to leave ideas on the discussion page.--Arjs 08:18, 17 September 2007 (EDT)

  Is it possible to do dc level, and screen width of several seconds? That might both respond understandably to noises, and provide a foundational physical intuition for what the app is doing. MitchellNCharity 12:00, 17 September 2007 (EDT)

  Voice looks good on a spectrogram or waterfall plot, which you definitely ought to have. It looks even better on a cochleagram, such as this one. (ignore the distracting cartoons) AlbertCahalan 01:26, 18 September 2007 (EDT)

  Some of the visualization ideas on the box-of-tricks page are really quite fun. (Good catch Albert.) Someone should make a game out of them. --Walter 04:19, 18 September 2007 (EDT)

• Doing a demo, I noticed the wave of a high pitched whistle-with-lips was overlayed with an even higher frequency wave. Turned out the room had an ultrasonic motion detector to turn off the lights. :) MitchellNCharity 15:18, 19 September 2007 (EDT)
• A common oscilloscope demo is to touch the leads and watch your body resonating at 60Hz with the local grid. While this might not actually work for much of our target audience, is there an easy way to do it? The plastic case seems to prevent you from just using your finger. MitchellNCharity 15:18, 19 September 2007 (EDT)

Proposal for a concrete, viseral osciliscope interface

(Ted Selker) -A scroll on the left lets paper out, it wrinkles at the right side of the screen. -Imagine the input looks like a lightning bolt with its end pointy. The lightning goes up and down on a vertical area that looks a little like a scroll bar, the right side of the scroll bar has a dimple in the center that is attached by springy material to the inside of the bar. -In AC mode, the lightening bolt is attached to a spring at the center of the slider that constrains it to move around the center where it touches the side of the bar ink flows onto graph paper. -In DC mode the lightening bolt goes up and down, where its tip touches the right of the slider, ink flows out onto the graph paper that is rolling out of a spindle accross the screen and is all crunched up on the right, -The freaquency of the scan is controlled by pulling on a handle at the right which pulls paper out faster. -The gain is controlled by grabing the top andto stretch the graph paper vertically, of course numbers in millivolts and millisenconds and lines corroboarate the changes in gain and speed. -To look at old readings, one can grab the folded up area and scroll back in time. It is also possible to have a bunch of wrinkled paper between two streched out pieces to compare an old reading to a current reading on the oscilliscope. -For the frequency domainthe motor on the reals for the paper get replaced with a dashpot damped spring, the faster the frequency is the more often it is pushing the spring tighter, to go to the right it has to keep banging the system with the top of the wave. there is probably a flucrum and a hammer on a teater toter that is self adjusting to make the tops of waveforms or spikes bang the dashpot. In this way a graph of voltage / frequency can be made. -Other input sliders can be made; -an integratng input is just a slider in a viscous liquid, -a logic analyser is just a bystable spring that is either sprung or unsprung. Alternatively imagine a bubble in a level that is upside down so that the middle is the lowest place: if the level indicator is turned slightly to an angle, the bubble goes all the way to one, if the indicator is tipped the other way, the bubble goes all the way to zero.

The point of all these visual elements is to replace words and huge numbers of knobs with a concrete viserally changing things that can be fiddled with. By fiddling with these contiguous controls, one can see how changing them effects the recording device.

Proposal for a physical input sensor kit

(Ted selker) I am told that personal stereo earbuds are available for $.50 in third world countries.

If we plug the earphone into the mic input it does produce a signal that can be used as a microphone or to pickup vibration. If it is attached to a door, one could get a signal each time the door is closed. -Because the laptop can bias or not bias the input, we can switch this bias on and off. When we do this across the coil, its resistance and reactance will make the characteristic low current until the coil is saturated LR curve on an oscilloscope. I expect these ear bud to have about 100 milli-henrys but need to measure it. In this way the bias can be applied and taken off repeatedly as a square wave watching the thresholds of time change allows an algorithm to measure the inductance of the coil variously inserted completely or taken away from the magnetic core. This gives a DC response from the voice coil that allows us to make a LVDT linear sensor in software. -If we poke a small stick through the perforated holes without puncturing the diaphragm, it can push on the voice coil. If the stick is set up as a lever against the hole it goes through as a fulcrum, the sticks position against the springy diaphragm can be used as a measuring tool. if the apparatus is jiggled the stick will push the coil up and down as an accelerometer. this can be used to measure pendulum motion of a playground swing being the same frequency with different weight people, it can be used to show how much acceleration and deceleration a pulled sled, wagon or car has... -If the stick is positioned near some solid object as an anvil, a piece of paper can be slipped between the stick and the anvil to move the voice coil depending on the thickness of the stick. -If a hair is hung from the stick, it will deflect the stick connection to the voice coil a bit. if the stick is long enough the hair can be weighed by the deflection. If the stick is shorter, the hair can attach the stick to a paper clip that weighs envelopes, if the stick is very short, it can weigh a coin in a plastic bag hanging from the stick... other mechanical arrangements can change the ratios further for weighing many coins, or the such. -A piece of paper or leaf can be attached to the stick for it to measure blowing or wind. -The sensor can be enhanced considerably by affixing a stiff material over the part of the voice coil that covers the magnet. This shouldn't change the spring constant of the diagram and will make a better coupling to the lever. I suggest any tiny plastic circle cut from a soda bottle or packing material would be fine. The affixment could be super glue or a tiny bit of chewing gum. For that mater, connecting the lever to the voice coil with a tiny amount of chewing gum or even tree sap would probably be good. Also the perforated holes in the ear bud might be excellent fulcrums, but of course changing them with a knife or making a fulcrum that is placed farther away from the diaphragm will give a simpler to control mechanical system

Linear frequency scales are often yucky

This is how DC to 48000 kHz matches up with the sounds we use. A440, the concert tuning pitch, is just a few millimeters from the left edge of the screen on an XO. The rightmost "A" is 28160 Hz. Normal voice contains little useful data above 4000 and almost nothing above about 12000, placing the limit 1 to 3 octaves below that 28160 Hz A. That's about 1 to 3 cm from the left edge of the XO screen. AlbertCahalan 01:14, 25 October 2007 (EDT)

The above assumes a full 1200 pixel width. Obviously, a reduced width makes things worse. AlbertCahalan 01:14, 25 October 2007 (EDT)

BTW, displaying a keyboard like this would help people to understand what they are looking at. AlbertCahalan 01:14, 25 October 2007 (EDT)

The keyboard would look great in an activity that primarily focuses on sound. Not sure how this fit into the context of Measure which has broader applications. Perhaps a different activity built around sound would be really interesting... --Arjs 09:11, 25 October 2007 (EDT)

The keyboard makes things way less confusing. When somebody starts up FFT mode, how are they to even know what they are looking at? The keyboard also gives a quick way to tell linear scales from logrithmic scales. Measure's FFT mode does not really have broader applications than dealing with periodic waves; the keyboard thus makes sense. With the input port in AC mode and/or the microphone in use, you really can't do stuff much outside the range of human hearing anyway. You certainly can't do ultrasonic. In DC mode you could manage subsonic, but that's still frequency data -- and thus appropriate to represent with the keyboard. AlbertCahalan 12:20, 25 October 2007 (EDT)

scales needed in FFT mode

horizontal

• linear frequency (currently the only choice)
• logrithmic frequency (base 2 log)
• linear wavelength, possibly negated
• logrithmic wavelength, possibly negated (base 2 log)

vertical

• linear: sqrt(real*real+imag*imag)
• logrithmic: log10(sqrt(real*real+imag*imag))