Test and Measurement Tools
| Site: | QSC |
| Course: | Q-SYS Level 1 Cinema Training |
| Book: | Test and Measurement Tools |
| Printed by: | Guest user |
| Date: | Tuesday, 3 December 2024, 9:10 AM |
Description
Video Transcript
0:08
Welcome to the Test and Measurement tutorial.
0:10
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.
0:16
Now what we already have set up here is a basic signal path
0:19
which is just an Audio Player wired to a Parametric Equalizer, which is wired to a Meter.
0:26
Now if we were going out to an actual system this Meter would represent our output to our amplifier.
0:31
Before we test this signal path, let’s learn a little bit more about what the Test and Measurement tools do.
0:37
Now let’s pull a couple of generators out here, so we’re going to go to Audio Components,
0:42
and under Test and Measurement we’re going to pull out a White Noise Generator.
0:47
Now the White Noise Generator will produce some random frequency across the audio spectrum.
0:52
We also need a Pink Noise Generator.
0:56
Now the Pink Noise Generator produces some random frequency
0:59
that’s distributed uniformly in each octave band.
1:03
And then lastly we have a Sine Generator.
1:07
The Sine Generator produces a sine wave of variable frequencies.
1:10
For cinema applications, we actually have an alternative to the Pink Noise Generator that’s called the
1:16
Cinema Pink Noise Generator. You can find this component in the “Cinema” folder of the
1:21
Schematic Library, rather than the Test and Measurement folder.
1:25
The Cinema Pink Noise Generator simply uses a different corrective algorithm that matches the
1:30
existing cinema processor’s output, so you’d want to use this for Pink Noise in a cinema system.
1:36
Basically we can use any of these tools to make noise – a very specific noise if necessary,
1:42
but for our intents and purposes, it’s important that these make noise that we know will work.
1:49
Alright let’s grab an RTA which stands for Real-Time Analyzer.
1:53
The Real-Time Analyzer is going to measure your signal.
1:56
If we open up our control panel we’ll see that it gives this graph,
2:01
and this will show you the magnitude of the input signal across the audio frequency range.
2:06
Let’s switch over to an RTA that I already have connected to an Audio Player
2:09
so we can see this graph in action. As you can see we have our graph
2:13
kind of jumping all over the place based on our input response,
2:17
and we’ve got a few knobs over here that are going to let us adjust this graph to our liking.
2:22
First we have the RMS Response Time which adjusts how quickly the graph changes
2:26
in response to the input signal. Now right now it’s at ten milliseconds, but if we were to put this up to about,
2:34
oh let’s say about a second, it’s really giving us more of a smoother average
2:40
rather than if we have it at ten milliseconds it’s really giving us a real-time response.
2:46
Let’s move down to Maximum Hold Time.
2:48
Now this lets us select how long the maximum magnitude will be displayed before refreshing.
2:54
That maximum magnitude is represented by the red. So if we were to, for example,
2:59
crank this up to about three seconds, you can see that
3:04
red hands around a lot longer than if I put it all the way down.
3:09
Next we have Infinite Hold which keeps the magnitude
3:12
held on-screen indefinitely until a higher magnitude is detected. As you can see,
3:18
this red line is pretty much sticking right here and we can clear that with Clear Response.
3:25
So the Generator lets us create noise, and the RTA lets us monitor that
3:29
so now we can use these tools to monitor our audio problems.
3:32
Now to do so we have to route them somewhere in our signal path.
3:36
Now you could unwire your design and rewire the generator and the RTA into your design,
3:43
but there’s an easier way to troubleshoot your audio without having to interfere with your actual design.
3:49
We’ll be using two new components called the Signal Injector and the Signal Probe.
3:56
These two tools will let you hack into your audio signal at any input and output pin.
4:02
Inside their components you’ll find these little diagonally-labeled tools,
4:05
which you can drag into your Schematic and attach anywhere in your signal flow.
4:11
Let’s do that, close these up.
4:14
Now first, we’re going to wire our White Noise Generator to our Signal Injector.
4:19
And now we can use our injector tool to inject this audio into our signal path.
4:24
Now what this means is that the Injector is going to override any other audio at the point of insertion
4:29
and then send out whatever audio is connected to the Signal Injector.
4:33
At this point it’s our White Noise. Now this means that you can inject some kind of digital noise
4:38
that’s guaranteed to work into your system so you can test out what’s going on.
4:43
Now we’re going to save our design right to our Core and run it.
4:48
So we’re at a good stopping point now, if you need to take a break go for it,
4:53
if not, continue on to the next section.
Lesson Description
This video introduces and defines the Test and Measurement tools; including noise generators, RTA, the signal injector, and signal probe.
Tips and Definitions
White Noise Generator: This component produces random frequencies across the audio spectrum.
Pink Noise Generator: This component produces random frequencies that are distributed uniformly across each octave band.
Sine Generator: This component produces a sine wave of variable frequency.
RTA (Real-Time Analyzer): This component produces a magnitude response graph of its audio signal.
Signal Injector: This component contains a tool that can be attached to any input or output pin, which will override the audio at that point with the audio that is wired to the Signal Injector component.