Hi fellow EEVbloggers,
I am a power supply designer and one of my tools of my profesion is the Frequency Response analyzer (FRA). For those who may not be familiar with what a FRA is, an FRA is used within the switched mode power supply community to measeare the open loop response of a power supply. However, measuring the open loop response is not its only use. The FRA can be used to measure complex impedance such a LCR meter and display it over frequency. There are at least 25 uses listed in the link belove.
We have many very smart people here in the EEVBlog who I am sure might be able to write some code to use the Agilent 2000/3000 scopes to emulate or have the same function as a FRA.
The Agilent 2000/3300 has an internal function generator (25 MHz) and has 2 or 4 matched input channels. It has all the required instruments already built in to do a manuel frequecy response measurement/Bode plot. Would there be anybody be up to the challenge of writing a code for the Agilent 2000/3000 that would basically sweep the function generator (sinewave) from lets say 1 HZ to 25MHz, and then have the oscilloscope measure the both amplitude and the phase difference between the two sinewaves. By sweeping the frequency and then measuring both the gain and phase angle and then plotting them on a graph or computer, you can generate the frequency response any any feedback system.
If there is anybody that can write the code and make a user friendly GUI, I would be willing to buy a linsense as long as its not too expensive.
The cost of the Venable FRA is about $30000, The Ridley FRA cost about $13000, and I think Omniron sell one for about $5000. As you can see these prices are out the range of the hobbyist. It would be nice to be able to have such a versitile instrument.
I have provided the links to the veneable FRA and to APinstument.
http://www.venable.biz/http://www.venable.biz/ap-25use.phphttp://www.apinstruments.com/files/Model300.pdfRobert
Frequency Response analyzer (FRA)... Venable FRA is about $30000, The Ridley FRA cost about $13000... Omniron sell one for about $5000... frequecy response measurement/Bode plot. Would there be anybody be up to the challenge of writing a code... basically sweep the function generator (sinewave) from lets say 1 HZ to 25MHz, and then have the oscilloscope measure the both amplitude and the phase difference between the two sinewaves. By sweeping the frequency and then measuring both the gain and phase angle and then plotting them on a graph or computer, you can generate the frequency response any any feedback system...If there is anybody that can write the code and make a user friendly GUI, I would be willing to buy a linsense as long as its not too expensive.
how much are you willing to pay? if you dont mind $500 or so, and the plot quality and timing/delay are not that stringent (thats usually the case with cheapo cost anyway), then there is already a PC software by a "guy" in this forum for that, you can pay the $500 for rigol DS1000 series and Hantek DS3X25 AWG, no need license because the SW is open free. but because unfortunately the software is only for the aforementioned devices combo setup.
The FRA can be used to measure complex impedance such a LCR meter and display it over frequency.
you may provide the "guy" with the information on how to calculate complex impedance from bode plot (freq respond) alone (if possible). i believe he still has the trouble of figuring out even the simplest complex impedance of a "real resistor" since the complex impedance analysis is there in the SW but still incomplete.
write some code to use the Agilent 2000/3000 scopes to emulate or have the same function as a FRA.
unfortunately the "guy" doesnt own Agilent DSO for testing and upgrading the SW for compatibilitiness, so he's totally out disqualified. thats why i suggested the $500 cost. good luck.
In use with SMPS would there not be a considerable problem with output voltage ripple and noise when using a scope operating over a wide bandwidth compared with the very narrow band tracking filter of a FRA?
Penfold,
Typically yes there would be problems with ripple noise. However, the Agilent has averaging and thar should be able to clean things up. Also you can use thr high resolution mode.
RB
Mechatronner,
Five hundred dollars would probably the most that I would pay. Who is the person who did the pc script for the Rigol ds1052 I WOULD ASSUME. I do have the Rigol function generator as well and if it could be made to operate with the scope it could work. However, I would prefer to have the Agilent because the function generator is already build in.
Rb
For such an application I propose to use Labview, both instrumets are supported.
The frequency sweep and the waveform aquisition is easy task.
I created similar application in Labview year ago for the Agilent E4980 wih ploting 3D graph (capacitance/voltage/frequency).
I'd rather stick a function generator chip and a microcontroller in a USB box and built a dedicated FRA. The problem is that the software will never be truly universal and depends on what kind of equipment people have. Labview is an option but did you check the price?
Mechatrommer,
This shows good posibilities of being very usefull. Did you write the software? Lets see if I got this correct. I download the software and connect the pc to the Rigol. I can then use an external function generator and sweep manually. As I sweep in frequency, does the software tell me to increase the frequency or does the software automatacally measures the frequency and plot it?
Can you explain how to use it with more details?
Robert
Hi Mechatrommer,
I tried the demo that you posted. I think I am getting the hang of how to use it. It does plot the correct gain and phase angle. If you could get it to work with the Rigol DG1022 and have the generator step and then have the scope measure and plot then you would a very system. I think you should get it to work (autamate) with other other function generator. I would try getting it to work with the Rigol generator since it is probably the most common function generator that hobbyist use.
I found another EEVblogger that wrote that he was working on making a Bode plotter for the Agilent 3000. I think his name on the blog is TP4. I sent him an message to see if he has made any progress in the FRA.
RB
Hi,
in attachment is the concept application in Labview , it is working with my DSO3034A, but sometimes it hangs (it seems to be related to LV 2011 or my version of drivers drivers.
Let me know if you want to try it. In case yes I will build the exe. Or try the .vi it in trial version.
It measure the phase and amplitude and put them into the graph and table (which is exported to log file as well).
The vavegen is connected to channel 1 and the measured device is connected to channel 3.
It was the first time when I use the DSOX in LV, so the construction is quite messy
Plesa,
This also looks good. I would be interested in trying it if you get it to work properly. Can the scope be configured or set to acquire in the average mode or high resolution. this would help in reducing noise.
how much would you sell the software.
RB
If you could get it to work with the Rigol DG1022
thats the problem. i'll wait future budget before thats possible.
I think his name on the blog is TP4. I sent him an message to see if he has made any progress in the FRA.
i think he is T4P? so i wish you luck there.
Plesa implementation looks the most promising. He is getting the data and then plotting it. Mechetrommers also looked good but only works with the Rigol ds1000 scope.
I pre fer to use the Agilent scope instead.
RB
Thanks Plesa,
I have my scope at work and won't be in until this Thursday. I will download it and give it a try.
Robert
If your scope has FFT and you have a noise source (like an AWG) it is a piece of cake to get a frequency plot. You don't need to sweep the frequency of the generator.
No, definitely not T4P. The person you are thinking of is KTP: