How to caculate the duty,fall time and rise time of signal

[Milky]

I am currently using Lv6.1, and have one NI GPIB-ENET/100 Controller, throught the oscillograph I want to caculate the duty of input signal, and it's fall time and rise time also, but, try it long time, I still no know how to do it, could you give me some tips? Examples is preferable.

Thanks.

[johnsold]

Can the oscillograph do the calculation and return the results or do you need to acquire the waveform and analyze it yourself? These are two very different problems. You will need to obtain the programming manual for your instrument and any LabVIEW drivers which may be available for it. Once you know what the instrument's capabilities are and how to communicate with it, then you can proceed to analyzing the data.

Lynn

[Milky]

Lynn, thank you.

The oscillographs in our lab are Tektronix TDS5104 and TDS7704, and I already installed related drivers in my PC, both for oscillograph and Labview.

The oscillograph can do the calculation and return results itself, but I want to calculate these results by myself, because I am no family with the programing command of these oscillographs . Now I can acquire the signal wave and calculate it's frequency and amplitude, but I found it difficult to calculate the duty and rise/fall time of the acquired sinal.

[johnsold]

I don't have LV 6.1 so I am not sure when some of these VIs were introduced. Under Waveform measurements are several VIs for Pulse, Amplitude, and Transition measurements. In Signal Processing >> Time Domain >> Pulse Parameters.vi is one that I think predates LV 6.1.

Depending on how noisy your waveforms are, you could also write you own VIs by getting Array Min/Max and Array Threshhold to define sgemants of interest.

Lynn

[Joe_H]

Programming these oscilloscopes is very easy using gpib commands I use the tds5104 daily and have written many programs for it. the driver vi's are very easy to use. I personally would just let the scope do it.

Here is an example vi converted to 6.1

and for 7.0

Message Edited by jhoskins on 08-19-2005 08:08 PM

[Milky]

Dear Joe sir

Thanks for give me these important information.  I will try it, and I would study the TDS programing manual carefully these days, if have any question, i will ask you later.

[Joe_H]

You may ask anytime. We all are glad to help.

[Milky]

Dear Joe

I had try with TDS programing commands in Lv6i, and I can acquire datas such as duty, frequency ,rise/fall time from the oscillograph directly, that's so inspiring me. Thank you.

But now I have another question to consult you.

I want to get more datas from oscillograph at "same time". According to the programing manual,"When you concatenate queries, the responses to all the queries are

concatenated into a single response message." 

I had try it(concatenate queries),  but fail to get the responses, it return nonthing, although I can write 8 commands continuely to the oscillograph sucessfully.

For example, i had write " measurement:meas1: type frequency;measurement:meas2:type amplitude;.......;measurement:meas8:type duty;" concatenated commands to the

oscillograph, the display change to what i want, but when i write"measurement:meas1:value?;.........;meas8:value?;" concatenated queries to the oscillograph to acquire the

result datas, it return nonthing. and if i read it one by one, that's ok.

So, how can i read many datas use the method of "concatenate queries"?

Due to my poor english, i don't know if i had make my mind clear in here.

Thanks.

[Milky]

I had encouter another problem tonight.

I want to make commands through the "formate into string.vi" or "Number to decimal string.vi", but i found if the input number of  Measurement. Select>7, that it will return zero result. While i want to get " Measurement:meas8......"command, but the result is "Measurement:meas0...."

I had check it long time, but i found no any fault.

what's wrong?

[Joe_H]

Hi.

Inorder for you to be doing it this way you must be sending over straight gpib commands, WHY, just use the drivers that are provided for the instrument pick what you need to do then if you want everything together in one string just manipulate it inside labview with that said to answer your question the concatenate and the format into string appear to be the same However in my experience with the 5000 series scopes you must have the measurement on the screen. use your program to set up the scope without pulling the values out. then check the scope to make sure the measurements are there the should be. If they are not then something is wrong with your setup progam. Sorry i could not help more.

Personally I would just use the driver as they are. Like I have said before do not try to reinvent the wheel becaus ewhen you are done it will still only roll, just like the one that was invented before yours.