Thread: Analogue Chart Recorders

Does anyone know if its possible to put an audio signal into an analogue chart recorder? If so, what kind of inputs would it need? Any information would be a big help!

cheers.

An analog chart recorder would be too slow to record an audio signal. You could get something like a triggering oscilloscope to record the audio signal and print it out. I'm assuming you just want to record some quick event. A continuous recording of any lengthy audio signal would require miles of chart paper.

Well its to record viewers coming in and out of a gallery space, so as when they make noise it is immediately recorded onto the graph paper. The paper would be looped, so as the recorder would go over what has previously been marked.

If I were to use an oscilloscope connected to a printer, would there be a way of keeping the immediacy of a chart recorder? Also would the oscilloscope input be able to take a microphone?

I think you are wanting a seismometer, no? You don't actually want to "record" an audio signal, but rather the "envelope" of it so you can see that people were in the gallery?

That's do-able. One would need to know the sensitivity of the chart recorder -- how much signal does it need for full scale, volts & (milli-)amps. A microphone and preamp would probably be enough to drive it, but you might possibly need a small power amp. Then I would use a diode and a capacitor to "filter" the signal, basically slow it down before feeding the recorder. Look up "envelope follower" for some ideas.

I'm still not clear on the type of effect you are looking for. If the chart were a paper chart with ink, and if you put it on a loop, it would keep writing over itself and after a few loops, you would just get a big blur.
At first I thought you wanted an analog signal of the sound. So if you had a 60 cycle hum, it would be a sine wave, with a frequency of 60 cycles per second. Now if you just charted that with a paper that is moving say 10 inches per minute, then you would have 60*60/10=360 cycles in one inch of chart paper. You couldn't actually see the individual cycles at that rate.
Maybe you just want something that records the loudness of the sound, like the deflection of one of those meters on a tape recorder.
But to answer one of your questions, yes you can input a microphone into an oscilloscope.

You can get sound level meters with built in data logging, such as this one. I'm sure some models also have outputs for external recorders.

okay, this sounds pretty interesting.

so would something like this:

http://cgi.ebay.co.uk/PHARMACIA-LKB-...item414eeea561


be able to record a wave form from this:

http://www.stagebeat.co.uk/product.p...source=froogle

?

Plus, the idea is that gradually the graph paper gets more and more blocked out as the pen goes over itself x amount of times. This is so as the viewer essentially becomes a part of a different form of sound recording (instead of one that is heard it is one that is seen; the viewer could potentially be looking at the sound recording of someone who made a noise 30 mins ago etc).

Thankyou so much for your help on this by the way, it will not go without a huge mention to each of you! you're all life savers!

Those two things look like they'd do your trick. At least, intuiting from the specs on the page, I think the Sound Level meter has a data output...

If you are adventurous, or cheap, you could pass on the SPL meter and find anything that has a microphone, pre-amp, and a "line-level" output -- like an old cassette recorder. At least for a start you could save a little cashola.

Your best bet would be to build a small detector circuit to enable the chart recorder to follow the envelope of the sounds, to follow the individual waves would be out of the question (as indicated by harold). essentially it would consist of a single diode, a small capacitor and possibly a resistor.

just an update:

I have everything now and am just waiting to install it all in the space. Once I have I will upload pictures of it since you've all been such a big help on this and deserve a position in the making of this piece!

again, thankyou!!