Fir notch filter design.(using DFD tool kit)
Hi
We used standard narrow band lowpass FIR filter design vis to desin a filter which can filter out any signal between 0.1 hz to 5hz. This does generate a filter design but is of a very high order, hence takes a very long time to process the raw data. Our raw data is of about 5000 samples and probably need to have higher samples when acqiring in the lower band frequencies,(say 0.1 hz or 0.5 hz).
Presently the need is to design a filter with folllowing characteristics:
1. Phase linearity to be maintained in the pass band.
2. sharp cut off freq band (can be the best possible to optimize speed of computation).
3. speed should be optimized.(require fast)
4. signal is mostly sign waves with noise riding on it.
5. High sampling rate is necessary to maintain the shape of the sign wave since we are more concerned with the phase of the input signal.
I have attached the snap of our design, (we used "DFD Narrowband Filter Design.vi"), which already uses the cascading technique.
thanks and regards,
sunil
Apna Technologies and Solutions
Bangalore,
Karnataka,
India
Attachments:
snap of FIR narrow LPF.JPG 63 KB
Hi,
Thanks for the reply.
The vi is designed but we are having an issue of speed of processing.
This filter takes a long time to process.
We are looking for the following:
Since our signal can range from 0.1Hz to 5Hz our sampling freq needs to be higher, about 8000 samples/s, this is necessary since the shape needs to be maintained for accurate phase measurements (the signal is always sinewave and with noise on it).However you may suggest this sampling rate based on your experience.
Since the phase in the pass band needs to be linear we have to select FIR and since the filter roll off needed is very sharp as provided in the attachment, the resulting design has a large number of taps(coefficients), this makes the processing slow.
--What would be the appropriate sampling frequency for such a filter design.
--Is it that such filters are slow, if so how can they be put in the front end filtering of signals acquired from a daq (PCI-6229)analog channel in a continuous acquisition mode.
we would be thankful for a quick response.
PLS refer to the attachment for filter characteristics.
thanks & regards,
sunil
Apna Technologies and Solutions
Bangalore,
Karnataka,
India
Similar Messages
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Narrow Band Pass filter using DFD tool kit.
Hi,
This is in continuation of my other posts for the same subject. We are now designed a working filter but are presently facing some problems as mentioned below:
The filter does not work for any input frequency which varies in the second decimal place,
Eg
if the input freq is say 2.15 Hz the filter does not work well, we observe amplitude errors and some random dips in the amplutude response, however the freq is ok.
With all settings the same and only the input changed ot 2.1 Hz the filter starts to work fine.
This phenomenom is observed over the either filter range of 0.1 Hz to 5 Hz
In brief, our porblem is that, while acquiring dynamic signal from a daq (NI 6229), we may encounter any signal between 0.1 hz to 5 hz, since it is an analog signal and the freq can go to an accuracy of at least 10 exp -6 we are not able to filter these signals since out filter can filter signal only up to the first decimal place which is 10 exp -1.
We are attaching a doc to this post. containing further details.
We are in a time critical situation.
Thanks and regards.
sunil
Attachments:
Details of the filter settings.doc 47 KBHi,
Thanks for the reply.
The vi is designed but we are having an issue of speed of processing.
This filter takes a long time to process.
We are looking for the following:
Since our signal can range from 0.1Hz to 5Hz our sampling freq needs to be higher, about 8000 samples/s, this is necessary since the shape needs to be maintained for accurate phase measurements (the signal is always sinewave and with noise on it).However you may suggest this sampling rate based on your experience.
Since the phase in the pass band needs to be linear we have to select FIR and since the filter roll off needed is very sharp as provided in the attachment, the resulting design has a large number of taps(coefficients), this makes the processing slow.
--What would be the appropriate sampling frequency for such a filter design.
--Is it that such filters are slow, if so how can they be put in the front end filtering of signals acquired from a daq (PCI-6229)analog channel in a continuous acquisition mode.
we would be thankful for a quick response.
PLS refer to the attachment for filter characteristics.
thanks & regards,
sunil
Apna Technologies and Solutions
Bangalore,
Karnataka,
India -
I'm trying to make a sharp notch-type digital filter to remove the 60 Hz frequency noise in my signal. The NI Digital Filter Design User Manual shows an easy and efficient way of doing it using the DFD IIR Notch Peak Design VI. I downloaded the Digital Filter Design demo to try it out. The problem is that I cannot find the Notch Peak Design VI among the demo files. Is this VI part of a library that you only get if you purchase the Digital Filter Design toolkit?
Thanks,
-- Ilkka L.Hi Ilkka,
After downloading and installing this toolkit, there are a couple of things you can try in order to determine if all the tools are indeed in place on your system or not. One thing I'd recommend is to do a search within the Functions Palette to determine whether or not the needed VIs are there. If the toolkit did indeed install correctly, you'll find a whole sub-directory of VIs within Functions>>Addons>>Digital Filter Design. These VIs are what you would need in order to build a customized application or to run the included examples. This leads me to the second recommendation: If everything is in place on the system, you will find the Digital Filter Design examples under the 'Toolkits and Modules' section of the Example Finder.
Let me know how these searches turn out and we'll see what we can do from there.
Peter
Peter L.
Applications Engineer
National Instruments
www.ni.com/support/ -
How to design a good 60Hz notch filter?
I tried to design a 60Hz notch filter(59-61 as stop band,tried different kind filters/orders,cont.true)But I can't have a stable output. When test on 60 Hz input,the output signal's amplitude will change in a repeated pattern,sometime the ripples is very small, but sometimes it's big, especially at the waveform beginning. The Fs is 5000, data is sampled every few seconds. Are there any refined 60Hz notch filter can be used, or any better way to design a notch filter?
Averaging is one way to remove the ripples after filtering,but I hope the filter can give a steady output.Thanks!sfhj wrote:
please if you have this example or know about it ,send it
thanks
@sfhj
Hijacking a old thread is never a good idea. I suggest you start your own. Also in order to get help you must explain better what you have done so far, why and how you struggle. The best way to do this, is to post your code, and some signals examples. I know a lot of tricks. And none of them need a fancy toolkit. But you must start your own thread in order to get help from me.
Edit: I noticed you have started a new thread, do you want to move the discussion to that thread?
Besides which, my opinion is that Express VIs Carthage must be destroyed deleted
(Sorry no Labview "brag list" so far) -
hi i need to design a notch filter for eliminating ECG hum..i am working with NI ELVIS work station...and LABVIEW 8.0. Unfortunately it needs an addon software "Digital filter design toolkit", which i dont have. Its urgent..can some 1 plzz help me out.
Hi and Happy Halloween,
Depending on the license you have for LabVIEW and the toolsets you have installed, you may be able to have a "notch" filter. I would search your pallet for "Bandstop" because a notch is a type of Bandstop filter. Or, you can make a notch out of a high-pass and a low-pass or you can use the filter express VI. If these VIs are not on your pallet than you probably only have the LabVIEW Base and thus, cannot use these options.
Charlie M. CLD -
Cannot use DFD IIR Comb Filter Design in my application
Hi everybody,
I am filtering power line noise 60 Hz and its harmonics (120Hz, 180Hz,..) using Comb Filter Design. I do the same as the example in LabVIEW, but it does not work.
Anyone help me how to put that Comb filter into my application?
Thank you.
Attachments:
Comb Filter.vi 83 KBHello mipro,
When you say you do the same as the example do you mean the one at this link?
https://decibel.ni.com/content/docs/DOC-14292
And when you say it does not work, can you please be more descriptive. Are you not filtering at all? Can you post pictures showing your results in comparison to results you expect from using the example that you were talking about?
Regards,
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National Instruments
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Is there a way to simulate a notch filter in CVI?
Hi
I am pretty new to CVI. I've only used it for a course in university.
I'm wondering if CVI can do things that Matlab can do. For example, a notch filter is very easily implemented in Matlab.
Is there a way to create a notch filter in CVI?
Thanks,
JasmineHi Jasmine,
In the CVI Library you should find a Advanced Analysis Library. From there go to Signal Processing»FIR Digital Filters and look for any function that ends in _BSF (Band Stop Filter). These functions will give you the coefficients for a filter and then you would convolve it with your signal to filter the signal. Here's some example code that comes with the Wind_BSF filter:
/* Design a 55-point bandstop FIR
linear phase filter that can achieve at least a 44 dB attenuation and filter the
incoming signal with the designed filter. */
double x[256], coef[55], y[310],
fs, fl, fh;
n, m, windType;
fs = 1000.0; /* sampling frequency */
fl =
200.0; /* desired lower cutoff frequency */
fh = 300.0; /* desired higher
cutoff frequency */
/* stop band is from 200.0 to 300.0 */
n = 55; /*
filter length */
windType = 3; /* using Hanning window */
m =
256;
Wind_BSF (fs, fl, fh, n, coef, windType);
Convolve (coef, n, x, m,
y); /* Convolve the filter with the signal. */
I hope this helps!
Tanya V
National Instruments
LabVIEW Platform Product Support Engineer -
Filter Design Problems - Labview 8.2
I am trying to designe a filter to replicate the frequency weighting curves in ISO-2631-4.
These curves are specified (in third octace steps) between 0.1 and 400 hz
I have based my design on the "DFD least Pth Norm Design.vi"
I have created the band specification array but in my vi I do not appear to be getting anthing out of the "DFD Get Freq responce.vi"
Any thoughts
I quite new to filter design, Am I using the right technique? If not how should I be implementing this filter?
Attached is my vi
Thanks
Attachments:
RQ Filter.vi 40 KBdehmann wrote:
Wow, thank you for the diagram tbob. The program outputs correctly. I've been searching for help for almost 3 weeks now. I have a few remaining questions. 1) Why did you choose to use shift registers instead of indexing nodes? 2) What exactly is writing the data inside the loop? 3) How do I make the program write every 100 ms instead of once every cycle? 4) Do you have any other tips for programming? Thank you so much for your help.
1) You are using a For Loop which can run 0 times if the input to N is 0. With regular terminals, if this happens, the output terminals will be at default value and you will get an error on your Close function after the loop, and the file will not close. Causes memory problems. Also if there was an error before the loop, the default error (no error) will occur after the loop and you lose your error. With shift registers, the values going in (error and file reference) will be carried to the output if the loop does not execute and the file will close normally and the errors will be reported. This was a suggestions given to me by NI in one of their training classes.
2) The Format Into File function will format the data according to the input format string and then write the formated string to a file.
3) Make the cycle 100ms and then write once every cycle. This is the easiest way to do it. Make the delay 100ms to do this. You gather data every loop cycle so just write once every cycle. Why would you want to write the same data more than once?
- tbob
Inventor of the WORM Global -
Install Digital filter design toolkit on labview 8
I get an error that says:
You must install labview FDS or PDS 7.1 (or later) before
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I have only Labview 8.0 installed.Hi storeytime,
Are you running LabVIEW in evaluation mode or as Base Version, than this could be the reason why it doesn't work.
You have to activate LabVIEW as Full Development System (FDS) or Proffessional Development System (PDS) to install the DFD Toolkit.
If you have allready activated LabVIEW as FDS or PDS you need to start it once to get the registry updatet, then the installation of the Toolkit should be possible.
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How to apply notch filter in the PID control
Dear all,
I am using PID control in my positioning stage but the output is every noisy with some fixed frequencies(30,50,150Hz). I want to add a notch filter to take off those noise. However, I do not know how to apply the notch filter to the PID module. Could anyone tell me how and show me example if you have?
Thanks
best
Attachments:
PID_notch filter.png 21 KB
PID_notch filter.png 21 KBHi LYnn,
I am sorry for my late reply. My stage is driven by a voice coil actuator (VCA). The VCA as a resolution of 1 um and range of 6 mm. The NF of the stage does shift when the load is changing. Do you have any advice for controlling such kind of stage?
BTW, as far as I see, the control frequency is determined in the DAQ Assistant settings and its value is equal to "Sampling rate"/"Samples to read", am I right?
Thanks
best
Attachments:
VCA stage.png 160 KB -
How to install PL/SQL web tool kit for designer 6i
HI,
I was going through the tutorial supplied by the evaluation
version of Designer provided at OTN. there it required PL/SQL
web tool kit to be installed, but when I run the web tool kit
generator, it gives me error.
Where can I find the PL/SQL web tool kit, which I can install in
the database directly, I don't want to install Oracle 9iAS. As I
know web tool kit is available in it.
SreekantTo run WEB PL/SQL in Desgner, you just need to run the following
package in databse user, where you want all your schema objects
to be:
<<Designer Home>>\Cgenw61\Cvwetc\Wsgl.sql
After this, just create a DAD entry with a Database Connector
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Vishal -
I have recently had to fire my web designer who was using iWeb. Now I'm trying to figure out how to get the site to open in iWeb on my new MacBook Pro. Is there a way?
Firstly iWeb CAN'T IMPORT any kind of published html code as it has no import facility. You can however add html code, javascript and css by selecting the html snippet and placing it on your page the entering the code in here and clicking on Apply. You DO NOT create a shape as you say - you use the html snippet and place your code in there.
There are not really a lot of ways in which you can write code - if you want to enter small amounts of code, then you would use an ordinary text editor to do this such as Text Edit on a Mac or Text Wrangler. If you want to add code to iWeb like this, then you would either use the html snippet method in iWeb itself or you would have to publish the site to a local folder from iWeb and open the relevant html page with a text editor and add the additional code in this way and then publish. However, if he decided to add the code with a text editor, then you would have to upload the pages directly to the server using an ftp client - if you try to upload the site directly from iWeb, all the extra code will be overwritten.
As for checking whether the site was created using iWeb, all you need do is view the site in Safari and then click on View and then select View Source Code and it will tell you.
Even thoough extra code was added to the site and he might well have done this by publishing to a local folder and adding the code with a text editor, he should still have the domain file for the site too.
Ask again. I'm sure that for adding quick code, most would not want to use programmes such as Dreamweaver, but a simple text editor will suffice. As OT already said, if he claims that he does not have the domain.sites file, then try Flux 4 which is a web design programme and has full import facilities. At least this way, if he just gives you the published version of the site, you have some way of opening it.
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Digital Filter Design Toolkit for LabVIEW 8.0
I need Digital Filter Design Toolkit for LabVIEW 8.0 and I cannot find it on the site.Where can I get it from?
Contact your local NI representative. He might just sent you one.
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How can I eliminate a ringing noise from a 60 Hz analog notch filter?
Using 60Hz analog notch filter may cause some ringing noise for the signal of cutoff frequency edges. Do you have a method excluding such a ringing noise? I guess that a deconvolution method will be helpful for the problem but I cannot apply that properly.
ELCA,
A different approach is to average in the time domain.
I suggest a method called 'boxcar' used in physics labs sometimes.
Slice your time between two triggers in let's say twelve equal time slots and do a lowpass (f0) on
each slot.
The result is a stepwise approximation of your curve. In the frequency domain this is about the same
as a bandpass at the cardiay frequency with the bandwith f0
60 Hz signal is problem only if your rats heart beats inside this bandpass. But when it is at 60 Hz
you might have lots of difficulties anyhoe ;-)
Urs
ELCA schrieb:
> Ron,
>
> My signals are the cardiac beatings of a rat through a 60 Hz analog
> notch filter. For averaging, I obtained several dozens of epochs with
> a fixed trigger
positon.
> I tried averaging the epochs in the frequency domain(FFT and averaging
> only for the amplitude) and took the inverse FFT of the averaged
> signal. However, the result was not satisfactory. It gave me a more
> noisy shape and still 60 Hz ringing. If you have some comment about
> that, please let me note that.
>
> ELCA -
How to interpret the Coefficient Report from the FXP Digital Filter Design
Hi, I tried to design a low pass IIR filter in cascaded form II. I then pass the filter into the filter structure conversion VI and then pass the filter into the FXP conversion and get the Coefficient Report.
However, I got problem understanding the report. The index of the coefficient does not correspond to the description of the Filter structures in the Labview help:
In the labview help where they describe the filter structures, the coefficients have two indices, one for the stage, and the other for intra stage.
In contrast, the report only gives out coefficients with one indicices.
My question is: how to map the coefficients to the structure.
Attached is the digital filter structures appeared in the Labview help.
The following is the report:
Reference Value Quantized Value Note
Forward Coefficients:
b[0] +1.0105197822678145E-6 +1.0104849934577942E-6
b[1] +2.0210395645356291E-6 +2.0210864022374153E-6
b[2] +1.0105197822678145E-6 +1.0104849934577942E-6
b[3] +1.0105197822678145E-6 +1.0104849934577942E-6
b[4] +2.0210395645356291E-6 +2.0210864022374153E-6
b[5] +1.0105197822678145E-6 +1.0104849934577942E-6
number of Overflows: 0
number of Underflows: 0
number of Zeros: 0
Reverse Coefficients:
a[0] -1.9962855130669792E+0 -1.9962768554687500E+0
a[1] +9.9628955294911659E-1 +9.9627685546875000E-1
a[2] -1.9984573661467793E+0 -1.9984741210937500E+0
a[3] +9.9846141042409486E-1 +9.9847412109375000E-1
number of Overflows: 0
number of Underflows: 0
number of Zeros: 0
gain +1.0000000000000000E+0 +1.0000000000000000E+0 Floating-point
* Gain processing is on the host
Attachments:
IIRcascaded.GIF 7 KBHi David,
The following Developer Zone article discusses important concepts involved in utilizing the digital filter design toolsets. It specifically address the form in which the design coefficients are expressed.
I hope this helps.
Cheers,
Emilie Kopp | National Instruments
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