knob control

[Dennis_Knutson]

2. In the VI you posted, the X scale is set to auto. I thought the Y scale was also set that way but it's not. Yes, placing set property node in an event structure will mean that you would write to the property only when the value of the knobs change.

3. What the button on the scope does is probably explained in the scope manual and may change depending on how you have set the trigger options. Since you are using the autosetup, there is almost certainly a default trigger that is being used. I would imagine that the defaults are explained somewhere there. You should also be able to manually view the trigger setup after doing the autosetup.

[Phobia]

Ok. Topic 1 and 3 I am going to manage myself.

Regarding the autoscale, I was making experiments and probably forgot to change it back to disabled. When I run the VI, I always do it with both disabled.

About topic 2, just one last question. Atfer changing the property node from inside the loop into the event structure, am I going to control both minimum and maximum values of the scale at the same time with one knob, making the signal always centered? Or am I going to need to change/add something in the VI?

[Dennis_Knutson]

I don't know how you want to set the min and max with one knob. Obviously, the values for the min and max are going to be different. I also don't know what you mean by centered. The scope returns a single and complete acquisition and with autoscale, you see the entire acquisition. What exactly do you want to center? Have you looked at the Graph Palette options for zooming?

[Phobia]

You are missing my point. Like I said before, I don´t want autoscale. I want the scale to be controlled manualy by the knobs like a real oscilloscope.

In the beginning of this post, gak gave the idea of creating the scale maximum property node attached to the knob, so I can adjust the scale. The only problem is that it only moves in one direction (up), making the graph uncentered.

I wanted to have one knob to control both minimum and maximum values, so I can have the signal always centered. I thought that establishing a negative value for the minimum value on the graph scale and attaching both Scale minimum and maximum property node to the same knob, I could make it happen. For example, having the graph Y scale with a maximum value of 4 and a minimum value of -4, I thought that when I moved the knob to, lets say, a value of 10, the resulting graph scale was 10 for maximum and -10 for minimum (making the sine wave centered on zero). Of course it did not work, making both values positive.

Do you understand now what I am trying to do? I am out of ideas to make this work.

Thanks.

[Phobia]

Up

[Dennis_Knutson]

Since you do have an actual scope and if you want to control the timescale of the scope, your knob should be setting the scope through the driver and not modifying the graph. Manipulating either the x or y axis after the acquisition will have the affect of showing only a portion of what you aquired. This would be the same thing as using the built-in zoom functions. What of these two do you really want? For changing just the display, you could look at the example called Two Channel Oscilloscope. Used by itself, it will zoom the beginning of the waveform. You could use that along with the x scrollbar.

Message Edited by Dennis Knutson on 08-20-2009 08:35 AM

[RavensFan]

Please post whatever VI you have that is not working for you. If what you want to do is as simple as it sounds, then we'll have to see what you are doing to figure out why it's not working.

[Phobia]

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Ravens Fan wrote:
Please post whatever VI you have that is not working for you. If what you want to do is as simple as it sounds, then we'll have to see what you are doing to figure out why it's not working.

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I have posted the VI on reply #7.

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Dennis Knutson  wrote:
Since you do have an actual scope and if you want to control the timescale of the scope, your knob should be setting the scope through the driver and not modifying the graph. Manipulating either the x or y axis after the acquisition will have the affect of showing only a portion of what you aquired. This would be the same thing as using the built-in zoom functions. What of these two do you really want? For changing just the display, you could look at the example called Two Channel Oscilloscope. Used by itself, it will zoom the beginning of the waveform. You could use that along with the x scrollbar.

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I understand what you are saying. Indeed when I change the X Scale, at some point there is no more signal to the right or to the left. I could not understand why, but now that you explained it, it really makes sense.

In fact, for this project, the best option is to use the whole signal and not only a portion of it. Coul you explain it to me, how can I set this through the driver, please?

The objective of this project is to make a virtual scope, mimic all the functions I can of a real scope, and then access it remotely through GPIB, so I can use it without even touch it fisically.

The only downside is that I never had classes or any kind of preparation for this software. I have never used it before and they gave me about 2 months to make it happen. Due to the complexity of the software, it is not an easy task with so little time.

Thanks again for your time.

Message Edited by Phobia on 08-20-2009 10:49 AM

[Dennis_Knutson]

The example I mentioned is a virtual scope. You can use remote panels and access it from a web browser.

In order to truly emulate a scope through GPIB, you need to do quite a bit of work and the approach you are taking is not correct, imo. To truly emulate an instrument, you need to have a pc with a GPIB card (not set as controller) and write software that will read and parse GPIB commands and return appropriate data. For example, a basic function would be the *IDN? command. A pc would send this to your emulated scope. The software on the emulated scope would receive this and it decide to send some identifier string back. A sophisticated SCPI parser would be required on the emulator.

[Phobia]

The only cable I have (that was given to me), is a GPIB conector on one side, which is connected to the scope and USB on the other side, which is connected to my laptop. It came with NI software and drivers.