knob control

[Dennis_Knutson]

I think I got confused over some of the terms. By virtual scope, do you mean an actual scope that you have to control or are you trying to simulate an actual one?

To control the vertical and horizontal settings of the tek scope, you need to find the appropriate driver function. The driver has an example that you can look at. I would recomend that you place the horizontal and vertical knobs inside an event structure so that the commands are sent only when the knob is changed.

[Phobia]

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Dennis Knutson wrote:

I think I got confused over some of the terms. By virtual scope, do you mean an actual scope that you have to control or are you trying to simulate an actual one?

To control the vertical and horizontal settings of the tek scope, you need to find the appropriate driver function. The driver has an example that you can look at. I would recomend that you place the horizontal and vertical knobs inside an event structure so that the commands are sent only when the knob is changed.

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I have to make a virtual scope in labview, with functions that a real one has, like trigger button, volts/div and time/div scales, X and Y position, etc. Then I have to comunicate remotely with the real scope through GPIB to receive the signal from the real scope. Finally, using only labview, all the functions of the virtual scope have to function like the real thing.

Hope your not still confused.

About the second part, I changed them to an event structure but they stopped working. Do not know if it is needed to add a clock or something like that to the time conector in the event structure. Anyway, I am going to explore it even more.

[Dennis_Knutson]

For the simulated scope, I gave you the name of the example. It would be the best place to start.

As far as the actual scope, look at the example for it to see the functions you need to call for vertical and horizontal settings. If you added an event structure and something no longer works, you should post the modified VI. Besides the value change event, what else do you have? Did you place the actual acquisition in the timeout event?

[Phobia]

I finally found the VI example you mentioned. I think it is going to help very much.

I am going to study the example, try to implement some things in mine and then I´ll get back to you if needed.

Thanks very much.

[Phobia]

Hi again.

So after more experiments and testing, I reached the VI that I am sendind attached. Thanks to the helpful example, I finally have the knobs the way I wanted. Just have a minor sitback with the frequency knob.

Let me know if I have this right (use attached "knob_config" image for guidance):

1-Minimum value of the scale

2-Maximum value of the scale

3-Sequence value (if minimum value is 0 and sequence value is 2, the scale will be...0, 2, 4, 6, 8...and so on until it reaches the maximum value)

4-?? cannot understand what it is...but this value is always the same with every case. It seems the lowest sequence value used in all the cases

5-?? did not understand why but it is always the same value as the minimum value of the scale (point number 1)

I was also trying to make a trigger function but ended up leaving the idea, since it was too complex for me to make. Even with some examples, I could not reach a way to make it happen!

Now, I just want to make a simple thing that can read the amplitude and frequency values of the wave. I searched all the drivers functions and the closest

thing I got was a max and min waveform array which I created indicators for it. Ended up discarting them, because that is not what I wanted.

Then I tried to add a "Tone Measurements" function from signal analysis, but cannot make it to work, giving the connection error in the attached image "error.jpg". This function is perfect for what I need, since I only have to connect the signal and then add numeric indicators to amplitude and frequency.

This seems a very simple thing, so I do not understand why I cannot reach it by myself.

Hope you can help me out, once again!

Thanks very much for your time.

[RavensFan]

Rather than guessing at the cluster, here is what you should do.

1.  Delete the cluster wires.

2.  Right click on the property node and select create constant.

3.  Replace the Bundle Cluster with a Bundle Cluster by name.

4.  Wire the constant from #2 into the top of that.  Wire the output to your property node.

5.  Now you have each element by name that you can match up with the various constants going in.

6.  Actually, if you do that, you really don't need the Bundle cluster functions, you would just type your values into the constant created in #2.  You can turn on the labels of the elements so you know which is which.

As for your error message, turn on context help and it will tell you the problem with your datatypes.  You just have to figure out what it is you have in that cluster of 3 elements and convert it to the dynamic data type.

Message Edited by Ravens Fan on 09-02-2009 04:46 PM

[Dennis_Knutson]

And the rest of the VI with your time base and Volts/Div is just plain silly. What you want to be doing is changing the Volts/Div and Time base of the scope. These controls should be wired to the function in the driver that sets these. If you do that and have the graph set to autoscale, you don't have to mess around at all with those property nodes.You'll be seeing the exact same thing that the scope is diplaying and you'll be actually controlling the scope.

Having used the tek scopes, I know that the cluster contains t0, dt, and a waveform array. Just connect the elements to a Build Waveform function. If you want continuous measurements, place the Express VI inside the loop. If you want to skip all of that, use the built in measurement functions of the scope. 

Concentrate on one thing at a time and try to realize the differences between a simulated scope and an actual one. You've completely mixed them up.