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spektrolyte · Joined: Jan 16, 2016 Posts: 23

My amp spits out a load of noise for about 3 seconds upon startup and this is affecting the session average figures.

Is there a way of muting the output of the source for a short length of time before allowing data through?

jarek · Joined: Oct 22, 2007 Posts: 1073

There is no direct option to mute like that.

But you could try to use the "Do not start" advanced property on your amp element, select it. Then use ElementInteractor along with Timer to start that element after 3 (or more) seconds.

spektrolyte · Joined: Jan 16, 2016 Posts: 23

OK I'll try that. Thanks :)

spektrolyte · Joined: Jan 16, 2016 Posts: 23

Now the burst of noise happens after the time interval has completed.

I could instead try applying the same idea to control the gain of a mixer element, effectively muting the signal until the noise is done

spektrolyte · Joined: Jan 16, 2016 Posts: 23

OK Mixer has no gain. Is there an attenuator element?

spektrolyte · Joined: Jan 16, 2016 Posts: 23

Or is there something that could multiply the float value of source output by zero for 3 seconds, then multiply it by 1?

spektrolyte · Joined: Jan 16, 2016 Posts: 23

Got it working with Timer, Element Interactor and Expression Evaluator.

There is still a spike, is there a way to ramp up the gain from 0 to 1 over 1 second?

jarek · Joined: Oct 22, 2007 Posts: 1073

Yes, you can create a more advanced expression for that. For example, in advanced properties declare:

float ratio = 0;

Then in the main expression do this:

Out1 = In1 * ratio;
if (ratio < 1)
ratio += 0.01; // Or other step, depending on how quickly you want this to happen

jarek · Joined: Oct 22, 2007 Posts: 1073

That last idea could be even used to replace your Timer and ElementInteractor, and use just ExpressionEvaluator.

spektrolyte · Joined: Jan 16, 2016 Posts: 23

It seems to work best with the timer as the gain is so high at the start there is still a huge spike even with the new expression.

Thanks!

jarek · Joined: Oct 22, 2007 Posts: 1073

The expression could be slightly different in such case, so that the gain stays at 0 for some time:

Declaration:

int idleCount;
float ratio;

Execute at start:

idleCount = 256*3; // 3 seconds at rate 256sps
float ratio = 0;

Expression:

Out1 = In1 * ratio;

if (idleCount > 0) {
--idleCount
} else if (ratio < 1)
ratio += 0.01; // This will increase from 0 to 1 over 100 samples
}

GMartin · Joined: Feb 5, 2010 Posts: 308

I am not sure if this would accomplish what you want. It seems as if you do not want you session averages distorted by the initial burst.

I have had a similar problem on some designs. I set the design to start when loaded. The edffilewriter, thresholds, and feedback are set not to start. After a few seconds I can click a button to start the processing of data and feedback. I do it this way so that I can start the session after I see
the signal has normalized. You could also set up a timer to start those processes.

George

GMartin · Joined: Feb 5, 2010 Posts: 308

I am not sure if this would accomplish what you want. It seems as if you do not want you session averages distorted by the initial burst.

I have had a similar problem on some designs. I set the design to start when loaded. The edffilewriter, thresholds, and feedback are set not to start. After a few seconds I can click a button to start the processing of data and feedback. I do it this way so that I can start the session after I see
the signal has normalized. You could also set up a timer to start those processes.

George

spektrolyte · Joined: Jan 16, 2016 Posts: 23

Good suggestion George,

I have to revisit this protocol anyway as there was a system error which removed all of the connections between the elements in that protocol.

It needs to be rebuilt at some point, and now I see the wisdom of using as many nested elements a possible.