Test and Measurement Tools

Welcome to the Test and Measurement tutorial.

In this video we’re going to take a look at some of the ways you can test a signal path in an active system.

Now what we already have set up here is a basic signal path

which is just an Audio Player wired to a Parametric Equalizer, which is wired to a Meter.

Now if we were going out to an actual system this Meter would represent our output to our amplifier.

Before we test this signal path, let’s learn a little bit more about what the Test and Measurement tools do.

Now let’s pull a couple of generators out here, so we’re going to go to Audio Components,

and under Test and Measurement we’re going to pull out a White Noise Generator.

Now the White Noise Generator will produce some random frequency across the audio spectrum.

We also need a Pink Noise Generator.

Now the Pink Noise Generator produces some random frequency

that’s distributed uniformly in each octave band.

And then lastly we have a Sine Generator.

The Sine Generator produces a sine wave of variable frequencies.

For cinema applications, we actually have an alternative to the Pink Noise Generator that’s called the

Cinema Pink Noise Generator. You can find this component in the “Cinema” folder of the

Schematic Library, rather than the Test and Measurement folder.

The Cinema Pink Noise Generator simply uses a different corrective algorithm that matches the

existing cinema processor’s output, so you’d want to use this for Pink Noise in a cinema system.

Basically we can use any of these tools to make noise – a very specific noise if necessary,

but for our intents and purposes, it’s important that these make noise that we know will work.

Alright let’s grab an RTA which stands for Real-Time Analyzer.

The Real-Time Analyzer is going to measure your signal.

If we open up our control panel we’ll see that it gives this graph,

and this will show you the magnitude of the input signal across the audio frequency range.

Let’s switch over to an RTA that I already have connected to an Audio Player

so we can see this graph in action. As you can see we have our graph

kind of jumping all over the place based on our input response,

and we’ve got a few knobs over here that are going to let us adjust this graph to our liking.

First we have the RMS Response Time which adjusts how quickly the graph changes

in response to the input signal. Now right now it’s at ten milliseconds, but if we were to put this up to about,

oh let’s say about a second, it’s really giving us more of a smoother average

rather than if we have it at ten milliseconds it’s really giving us a real-time response.

Let’s move down to Maximum Hold Time.

Now this lets us select how long the maximum magnitude will be displayed before refreshing.

That maximum magnitude is represented by the red. So if we were to, for example,

crank this up to about three seconds, you can see that

red hands around a lot longer than if I put it all the way down.

Next we have Infinite Hold which keeps the magnitude

held on-screen indefinitely until a higher magnitude is detected. As you can see,

this red line is pretty much sticking right here and we can clear that with Clear Response.

So the Generator lets us create noise, and the RTA lets us monitor that

so now we can use these tools to monitor our audio problems.

Now to do so we have to route them somewhere in our signal path.

Now you could unwire your design and rewire the generator and the RTA into your design,

but there’s an easier way to troubleshoot your audio without having to interfere with your actual design.

We’ll be using two new components called the Signal Injector and the Signal Probe.

These two tools will let you hack into your audio signal at any input and output pin.

Inside their components you’ll find these little diagonally-labeled tools,

which you can drag into your Schematic and attach anywhere in your signal flow.

Let’s do that, close these up.

Now first, we’re going to wire our White Noise Generator to our Signal Injector.

And now we can use our injector tool to inject this audio into our signal path.

Now what this means is that the Injector is going to override any other audio at the point of insertion

and then send out whatever audio is connected to the Signal Injector.

At this point it’s our White Noise. Now this means that you can inject some kind of digital noise

that’s guaranteed to work into your system so you can test out what’s going on.

Now we’re going to save our design right to our Core and run it.

So we’re at a good stopping point now, if you need to take a break go for it,

if not, continue on to the next section.