Bug: Issues in setting 1 microsecond scale in tektronix oscilloscopes

[Mathan]

Using tktds7k driver and LabVIEW 2009 in controlling tds 7404 oscilloscope as well as tds 7154 oscilloscope.

When the below code is executed, with the time scale set to 1 microsecond in tktds set horizontal parameters.vi, there is no change in the instrument and the previous time scale is maintained in the instrument. But if set it for 2 microsecond or lower values like 200 nanoseconds, the instrument scale changes as expected. I hope this is a bug in the driver. Please somebody confirm. Thanks for any explanation.

[Dennis_Knutson]

I don't have the scope to run the VI but its should be pretty simple to determine if there is a bug in the driver. Did you probe the string being sent to the VISA Write or capture it with NI-Spy. Compare that to the syntax in the manual or use MAX to send the exact same thing.

Curious as to why you are using the old driver with 2009 and not the current one for the scope. Have you tried the latest driver?

[Mathan]

---

Dennis Knutson wrote:

I don't have the scope to run the VI but its should be pretty simple to determine if there is a bug in the driver. Did you probe the string being sent to the VISA Write or capture it with NI-Spy. Compare that to the syntax in the manual or use MAX to send the exact same thing.

Curious as to why you are using the old driver with 2009 and not the current one for the scope. Have you tried the latest driver?

---

Thanks Sir,

But i have couple of questions. I just now installed NI -Spy and will post the findings.

1) Use MAX to send the same thing? How to do this? How to set Horizontal parameters settings through MAX?

2) why you are using the old driver with 2009 and not the current one for the scope - I have downloaded the instrument driver from here which i thought is the latest instrument driver. I forgot to mention one thing, my scope has Win 98 OS, so running LabVIEW in a remote PC with Win XP OS and in that PC, VISA 4.5 is installed (I will now update it to VISA 4.6). In the scope, VISA 3.0.1 is installed which is the latest driver i think.

Please advice if i am missing something.

Mathan

[Dennis_Knutson]

1. In MAX, go to Tools>NI-VISA>VISA Interactive Control. Just copy the string that is being sent or enter a command based on what is in the scope's manual.

2. When I drag the snippet to a block diagram, it tries to find the subVIs and the path is pointing to an llb - not a lvlib. If you were using the project style driver that I mentioned and that you provided a link to, you would not have an llb. The project style driver function names are also different than what you are using. The icons are different as well.

[Mathan]

---

Dennis Knutson wrote:

If you were using the project style driver that I mentioned and that you provided a link to, you would not have an llb. The project style driver function names are also different than what you are using. The icons are different as well.

---

Yes. You are right. I did installed tktds7k driver previously, that was quite a older one. I downloaded the Project style drivers and verified, the results are as expected as in the manual. But i need one clarification. In the manual,

Command         :HORIZONTAL:MAIN:SCALE 2.0000E-07;POSITION 5.0000E+01

Response         ;UNITS:VALUE 1.0000E+00;STRING "s";OFFSET 0.0000E+00;

Configuring for 200 ns in the command will yield 1 microsec in the response. Similarly, if we configure for 400 ns, it will display 2 microsec. (2 points down in the actual range - 200ns, 400ns, 1us, 2us, 4us, 10us) likewise it goes on.

One more thing, this project style driver i downloaded from the above page, is showing as DPO whereas previous one was TDS. I was very comfortable in using that TDS, since it was a very elaborated menu having all the options in separate subvis. I cross-verified with tktds7k driver again and the same issue persists for that one particular time scale setting (1 microsec). When i use raw VISA WRITE (Instrument IO --> VISA --> VISA WRITE) with the command as given in the scope manual, it is working fine. So i just use that when i need to set 1 microsec. Thanks for all the help.

Mathan

[Mathan]

With the previous driver i mentioned earlier, today i found another one weird behavior in setting 1 microsecond time scale. This happens in configuring trigger mode when setting the lower limit to 1 microsecond, the value is not getting set. For all other values it is working fine. No idea why this 1 microsecond is screwing up a lot in most of the cases.

I started using the latest project style drivers and to my surprise i didn't find the cursor configuration. Is cursor totally removed in this driver. Then how can i measure all the parameters? I need some helping how to measure the value of t1, t2, t3 from the following diagram. Please guide me how to measure.

Thanks, Mathan

Message Edited by Mathan on 10-21-2009 01:11 PM

[Mathan]

Dear Sir Dennis,

This is the palette view of the drivers. There is no functions for cursor controls. I need cursor functions to measure the time and voltage of particular point in a waveform. So that for the waveform in the previous post, i can measure t1, t2 and so on. In the new set of drivers this option is not there. I had a doubt whether the picture attached here is the full set of drivers or is it missing anything. Please also help me in measuring t1, t2.

Thanks,

Mathan

[Dennis_Knutson]

I had a look at the project driver and could not find any cursor functions either. I don't know why. Like many drivers, you will often have to modify them to suit your needs. Since the functions exist in the old driver, you can take those and add them to the project one.

[NathanT]

Hello Mathan,

       It seems to me like it might be better to read the waveform from the scope and then analyze it on your computer.  What do you think about that?

 Also you previously stated "...this project style driver i downloaded from the above page, is showing as DPO whereas previous one was TDS."  Can you please elaborate on that?  I don't quite understand since the Driver Identifier is Tektronix 7000 Series.

Cheers,

NathanT

[Mathan]

---

NathanT wrote:

 the Driver Identifier is Tektronix 7000 Series.

---

 Sorry for the confusion i made. Yes it is identified as Tektronix 7000 series only in the palette.

---

 It seems to me like it might be better to read the waveform from the scope and then analyze it on your computer.  What do you think about that?

---

Can you please elaborate this. Is it possible that i can do all the measurements that are done by the oscilloscope from the PC within LabVIEW after i captured the waveform? Let's take the case of above waveform where i captured the particular waveform from the oscilloscope and can i find the t1, t2 values from within the LabVIEW application? Please guide me in solving this problem. Thanks a lot.

Mathan