Butterworth Filter

I want to build a Butterworth filter with the formula node. what should I do?
Let's do it step by step and if you can correct me.
I saw the formula for the Butterworth is:
H(jw)=1/sqrt([1+(f/fc)^2n])
now I know that the cutoff freq. is fc=1/(2*pi*R*C) where R & C are variable and choosen by the user (this is what the teacher asked).
So if i write in the formula node this statments:
Tau=R*C;
Fc=1/(2*pi*Tau);
FdT=abs(1/sqrt([1+(f/Fc)**2*n]));
i got error. why?
Solved!
Go to Solution.
Attachments:
Exercise6.vi ‏7 KB

You were close. But your little loop inside the formula should look like this. Notice the perithesis around the 2*n. You were only squaring. You should raise to a power of 2*n. I added an input for the number of poles.
for ( f=0; f<1000;f++)
H[f]=1/sqrt(1+(f/Fc)**(2*n));
Also, there's an Absolute Value in the Numeric palette. Use that instead of the square and square root.
There are only two ways to tell somebody thanks: Kudos and Marked Solutions
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Attachments:
Exercise6.png ‏49 KB

Similar Messages

IIR Filtering and response .vi: Butterworth filter magnitude response depends on sampling rate -why?

Hi folks,
I am not expert in filter design, only someone applying them, so please can someone help me with an explanation?
I need to filter very low-frequent signals using a buttherwoth filter 2. or 3. order as bandpass 0.1 to 10 Hz .
Very relevant amplitudes are BELOW 1 Hz, often below 0.5 Hz but there will be as well relevant amplitudes above 5 Hz to be observed.
This is fixed and prescribed for the application.
However, the sampling rate of the measurement system is not prescribed. It may be between say between 30 and 2000 Hz. This will depend on whether the same data set is used for analysing higher frequencies up to 1000 Hz of the same measurement or this is not done by the user and he chooses a lower sampling rate to reduce the file sizes, especially when measuring for longer periods of several weeks.
To compare the 2nd and 3rd order's magnitude response of the filter I used the example IIR Filtering and response .vi:
I was very astonished when I the found that the magnitude response is significantly influenced by the SAMPLING RATE I tell the signal generator in this example vi.
Can you please tell me why - and especially why the 3rd order filter will be worse for the low frequency parts below 1 Hz of the signal. I was told by people experienced with filters that the 3rd oder will distort less the amplitudes which is not at all true for my relevant frequencies below 1 Hz.
In the attached png you see 4 screenshots for 2 or 3 order and sampling rate 300 or 1000 Hz to show you the varying magnitude responses without opening labview.
THANK YOU for your ANSWERS!!!
chris
Solved!
Go to Solution.
Attachments:
butterworth-filter-differences.png ‏285 KB

Hello Lynn,
thanks for the answer. You are right that there are few points "behind" the curve in the graph, see png.
However, this is the filter response which Labview (2009) provides to me directly out of the "IIR Filter for 1 Channel. vi" in the "filter information" output cluster. Where up to now I do not know how to influence it - apart from adjusting the input parameters "IIR filter specifications". OK, I assume I have to gain more knowledge of this. The curve of the magnitude resonse dies not change when I change the number of samples of the input signal of the signal generator, only wehn I change the sampling rate.
I used directly the example vi from Labview with the name indicated in my first post "IIR Filtering and Response.vi".
So I assumed that everybody has it in his/her examples shipped with LV and it is not necessary to post it.
I just adjusted the size of the diagram of magnitude response to see the curves better as you see in the attached vi.
So I did no changes to the vital parts of signal generation and filter of the example. The screenshots are like they come from the example when using the option "one waveform" where I as user assume that this which is behind is quality-controlled by NI.
I was also astonished that the filter magnitude response is different to the one I copied out of graphs 1 year ago - but I unfortunately cannot reconstruct which example I used there...
Thanks for any further comments
chris
Attachments:
IIR Filtering and Response_CH.vi ‏55 KB
butterworth2nd_order_bandpass_0p1to10Hz_mag_response.PNG ‏18 KB

How do I determine the best Order to run my butterworth filter at?

I'm lowpass filtering a signal that was sampled at 200hz through a 40Hz butterworth. I need to determine the optimal filter order. How do i create a quantitative comparison of the effects of the butterworth filter on the frequencies above 40Hz based on varying order?
I have tried using the FFT to create a chart in the frequency space, but am not sure how to proceed. Any help would be greatly appreciated. What I want to compare is the path immediately before and immediately after the butterworth filter.
Also is there an alternate way to read in a column of numbers from a text file without using the Read from Measurement file Express VI?
Solved!
Go to Solution.
Attachments:
frequencydomain.JPG ‏131 KB

I have my filter working correctly now. I just need a quantifiable way to justify picking any one order of filtering over another.
Here is my front panel, How can I compare the (After/ Before) graphs of varying orders (in a quantifiable way)? How can one tell which is the best?
I was thinking I could compare the (Integral from 0 to 40)/40 and the (Integral from 40-inf). The order that yeilds the closest to 1 and 0 respectively should be the one I go with. Does that sound logical?
How do I compute a definite integral with a lower bound and an upper bound?
Attachments:
order2.JPG ‏240 KB
order5.JPG ‏240 KB
order10.JPG ‏240 KB

Design a 1st order Butterworth low pass filter

Hey there... Really hope that u guys can guide me to solve these questions.. =)
Design a first order Butterworth low pass filter with cut-off frequency
fo = 20 kHz and the gain K = 1. You will need to simulate the circuit
using Multisim and shows that the circuit meet the required
specification.
i)Show all calculations steps and assumption made in your circuit design.
(DONE!)
ii)Show the circuit schematic with all the resistor and capacitor values labelled.(attachment)
iii)Perform frequency response analysis on the circuit and obtain the
bode diagram. The bode diagram should show the voltage gain (Vout /
Vin) in dB vs the signal frequency (0 to 100 MHz). Does the -3dB
cut-off frequency match the desired cut-off frequency fo = 20 kHz ?
Explain. From the graph, estimate the roll-off rate. (attachment)
I inserted my schematics and graph.. am i right?
Attachments:
Question 2a.zip ‏146 KB

Just an update for the community, in version 11 and 12 of Multisim, there are some circuit wizards available which can make designing some basic circuits easier. To access the filter wizard, go to Tools -> Circuit Wizard -> Filter Wizard. You can put in the parameters and Multisim will automatically generate the filter for you.
Hope this helps.
Regards,
Tayyab R,
National Instruments.

Band pass filter - butterworth.vi

I want to use a band-pass filter with a high cut off freq of 0.01 Hz and low cut off freq of 1 Hz. My sampling rate is 20 Hz.
Why does this not work?
It works if I switch the cutt of freq values, but I need it to work this way.
I use other applications that do this perfectly, I feel like I am missing something...
Thanks!!!!

It works just fine. If you want all the data suppressed to ~1E-18, that is.
The detailed help file for the Buterworth Filter VI states:
"The values for high cutoff freq: fh and low cutoff freq: fl must observe the following relationship:
0 < f1 < f2 < 0.5fs
where f1 is low cutoff freq: fl, f2 is high cutoff freq: fh, and fs is sampling freq: fs."
I suspect your problem is terminology. You want the high pass part of the filter to cut off at 0.01 Hz, meaning that it will pass everything above that frequency. But that is what LabVIEW calls the low cutoff frequency for a bandpass filter.
Lynn

In the filter scheme driver, how to i get the filename in open() or handleOpen ()

I want to implement filter scheme driver to monitor and prevent file open or read calls based on certain rules. For this I would need file name, user name and application process name. I did not find a way to extract this information. Any hint would be of great help.

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AND/OR + some nulls in filter

I'm running into another problem with the AND/OR filter.
The filter for selecting from object "a" and joining to objects b, c & d
is:
(b.theid==2 || c.theid==2 || d.theid==3) && active=="Y"
The SQL that gets generated is:
SELECT <...>
FROM b t1, d t3, a t0, c t2
WHERE ((((t1.theid = 2 AND t0.bid = t1.id) OR (t2.theid = 2 AND t0.cid
= t2.id)) OR (t3.theid = 3 AND t0.did = t3.id)) AND t0.active = 'Y')
This returns a number of instances of the same a object when some of the
OR clauses do not match. For example, if there's no record
with d.theid=3, then it will do a full join on table d.
Do I need to specify something else to flag these as potentially null
fields so that the filter parser adds that check in? The following SQL
query works
ok if I add some checks for NULL on those join fields:
SELECT <...>
FROM b t1, d t3, a t0, c t2
WHERE ((((t1.theid = 2 AND t0.bid = t1.id OR t0.bid IS NULL) OR
(t2.theid = 2 AND t0.cid = t2.id OR t0.cid IS NULL)) OR (t3.theid = 3
AND t0.did = t3.id OR t0.did IS NULL)) AND t0.active = 'Y')
Thanks,
-Mike
Mike Bridge

Hi D,
Thank you for your answer.
I have seriously thought about that solution; but I don't think it's a smart way to do it.
If i do it like that, i need to copy the whole table and paste it inside the if statements.
I have two xml elements that I need to make the decisions on. POH_PO_TYPE & CP_RELEASE_NUM.
POH_PO_TYPE can be: STANDARD, RELEASE or BLANKET.
CP_RELEASE_NUM can be: '' or N
If POH_PO_TYPE is RELEASE AND CP_RELEASE_NUM is not ''
OR POH_PO_TYPE is STANDARD
OR POH_PO_TYPE is BLANKET AND CP_RELEASE_NUM is ''
THEN show table (which contains the whole PO).
It shall show the content of the PO in any of these cases.
BR Kenneth

Jabber Windows - no phone control with LDAP Custom filter

I am unable to control the desktop phone from the Jabber 9.1 Windows client when the CallManager LDAP Directory uses a Custom Filter.
Has anyone else experienced this?
If I set the LDAP Custom Filter to <none> and save, then Desktop Phone control works great.
If I set it to use my custom filter, then trying to enable Desktop control just gives me the spinning circle, then times out to the Red X symbol.
I do not need to resync the LDAP Directory to get the error, just enable/disable the custom filter and save.
In both cases calling from the Computer works great.
This is an On-Prem deployment with full MS-AD LDAP integration.
Versions are:
Jabber - 9.1.0 build 12296
CUPC - 8.6.4.11900-1
CUCM - 8.6.2.22900-9
I upgraded to CUCM 8.6.2 SU2 last night hoping that would fix the problem, but no luck.
The LDAP filter is one I have used in numerous other clusters with no CTI issues.
It allows me to sync to the root directory, but only import active user accounts with an entry in the ipPhone AD attribute:
(&((objectclass=user)(ipPhone=*))(!(objectclass=Computer))(!(UserAccountControl:1.2.840.113556.1.4.803:=2)))
Thanks, Randy

Hi Randy,
Have you specified this base filter in jabber-config.xml file? As per Admin Guide:
"In some cases, base filters do not return query results if you specify a closing bracket in your Cisco Jabber for Windows configuration file. For example, this issue might occur if you specify the following base filter: (&(memberOf=CN=UCFilterGroup,OU=DN))
To resolve this issue, remove the closing bracket; for example, (&(memberOf=CN=UCFilterGroup,OU=DN)"
Thanks,
Maqsood

In ALV Report Filter selection should be case sensitive

Dear All,
since one field is case sensitive in database table , i have to fetch that in alv report , but when i am applying filter on that field its is simply fetching data with case description. if its in caps it should fetch caps data but in smaal case report showing no data
Regards,
Pankaj Vashista

Hi,
All text datas are case sensitive.
To make it work perfectly You have to Use the Keyword translate to Upper Case than display
Now filter can work.
Without Transalation to Upper Case filter will not work.
Regards
Arbind

My Mac is bypassing a website filter... How can I stop it?

I am a computer technician at our local high school. Right now, the school has about 800 Dell computers, but we are planning on introducing a few Macintosh labs within the next school year.
Since they lack educational value, the school district's director of technology (my boss) has a web filter (Deep Nine) that blocks myspace, facebook, youtube, proxy sites, and other similar sites.
Myspace is blocked via a keyword filter, any page containing the word "myspace" in the url, or in the document a set number of times, is automatically blocked. The other sites are simply blocked by URL. This filter works perfectly on our Dells, no one can access Myspace, Facebook, Proxies, etc.
I brought my Macbook to work today, plugged it into the network, and logged onto the internet. I noticed instantly that my homepage (Facebook) loaded without being blocked at all. Curious, I tested myspace and youtube, and I could get on youtube fine, but myspace remained blocked.
I checked on the Dell next to me, and all those sites will still being filtered and blocked. Yet my Macbook was able to access them without issue. So it would appear that my Macbook has some mystic ability to bypass the web address filter, but it can not bypass the keyword filter.
I do not have any proxies configured. My Macbook connects to the network (and thus, the internet) the same exact way the other computers within the school do, with the exception of the other computers being within Active Directory.
I need to find out if it is an issue with the Mac or with our Filter. I don't have any other Macs available to test with (Our only other Mac in the school is our DHCP server, and we do not use servers as "lab rat" computers).
Has anyone had any similar issues with this? Or does anyone know of any way I can diagnose this with only one Mac and only one Filter?
Specs: OS 10.5.5, Safari 3.1.2, wired networking.
Message was edited by: Joey Hogan
Message was edited by: Joey Hogan

The DeepNines product works well and does much more than a simple URL filter. The problem lies entirely in your district setup and not in their product. If you're not using a proxy filter, then you have all access and routes designed to head out on typical port 80 traffic to your isp and ultimately the internet hence no proxy configs. The filter is integrated with LDAP accounts at each of your locations to tell it which users and groups are to get filtered at what level. That tie in is what breaks down who goes where. If you introduce new macs onto the network and they have not been configured to work with the DN appliance and are going out unfiltered... then there are 2 problems here. #1 is that you have computers attaching to the network, receiving leases and doing what they want. Use DHCP reservations or a whitelist to control who gets on your network. #2 is that your DeepNines filter has not been set to failover to BLOCK. Instead, it's allowing unknown users to bypass freely simply because it doesn't recognize their group/account. And Orange, stop slamming the company. They are a smaller business that has taken a much better approach to filtering than any other large corporation. Standard database driven URL filters DO NOT WORK....PERIOD! I challenge you to call any district that is running their appliance to get their opinion of it in comparison to any of the other basic url filters out there. I did just that last week and they had absolutely nothing but high praises for the DN product. One even laughed at Websense which they had before switching simply for the lack of ability to block anonymouse proxies.

How to use one Filter Pane to multiple Dataproviders

Hi Experts.
i have checked the threads on this but i did not get correct solution.
we have issue in using single Filter pane web item in WAD for three different dataproviders ( three dataproviders have same free charecteristics and variable) charecteristics in row and keyfigures are different.
thanks in advance.
Regards
Raj.

Hi Gill,
Thanks for your Quick responce.
when we use the single filter pane, filter conditions are working for only first dataprovider (since data binding is to dataprovider 1. in affterted dataproviders i selected dataprovider 2 and 3, but filter pane is not active for other two dataproviders in tabs.
thanks in advance.
Any inputs please....
Regards,
Raj.
Edited by: Rajsapbi on Apr 6, 2009 9:22 AM

How to use property of dimension to filter the 2nd dimension in Allocation?

Hi experts,
How do we use a property of one dimension to filter out the members of another dimension in allocation script engine?
eg of two dimensions
1.)Entity dimension - (entity dimension)
memberset:                                        Channeltype (property)
                   Stores
                    Store1                           Boutique
                    Store2                           Kiosk
                    Store3                           Branch
                    Store4                           Concession
                    Store5                           Franchise
                  Nonstore
2.)business Channel dimension - (user define)
   memberset:
               Channeltype
                   Boutique
                   Kiosk
                   Branch
                   Concession
                   Franchise
                   Nochannel
in allocation code
*runallocation
*factor
*dim entity                          what=Nonstore;                where=bas(Stores)
*dim businesschannel        what=nochannel;             where= ? ;
*endallocation
The thing is that when the engine selected store 2 for entity it should select kiosk as its businesschannel.
Please advise.
Thanks as always,
yajepe

Hi,
In this case, I believe, you should have the allocation within a for loop. But you should note that the performance might reduce.
*FOR %VAR% = BAS(STORES)
   *RUNALLOCATION
   *FACTOR
   *DIM ENTITY WHAT = NONSTORE; WHERE = %VAR%
   *DIM BUSINESSCHANNEL WHAT = NOCHANNEL; WHERE = %VAR%.CHANNELTYPE
   *ENDALLOCATION
*NEXT
Hope this helps.

How can I create a filter for an exact set of characters?

Hello! I am setting up a filter to catch messages with GG in the subject. Sometimes this will be at the beginning of the subject (no space at the front) and other times it will be somewhere in the middle. The problem I'm having is that this filter catches any word with "gg" in it, like "logged" or "baggage" (one of my customers has baggage in their name, but their messages should not be caught by this filter). How can I make this work? Thank you for your time!

I think FiltaQuilla might be useful. It adds so-called Regular Expressions to the filter system, where you could use a construction like:
"subject regex" "matches" "/\bgg\b/i"
\b means a word boundary
gg is your two letters
\b is the trailing word boundary
/ and /i mean ignore the case, so it'll find gg, GG, Gg and gG.
There lots of ways of doing this. You could have
[ ]GG[ ]
where it would require a space (explicitly; nothing else!) before and after, and capital letters. \b is usually superior as it matches at the beginning and end of the line, and recognizes regular punctuation in addition to spaces.

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How can I filter a Sharepoint 2007 libarry list based on current user login?

Hi all.
I would like to know how I can filter a SharePoint library list based on current user login.
Suppose I have created the followings:
1) A SharePoint form library containing bunch of uploaded InfoPath form data.
2) The InfoPath form template contains a promoted text field called "TargetUser" to store user domain login (ex: DOMAIN\JOE) and every InfoPath form file in the library has a valid domain name stored in the "TargetUser" field.
I have created a custom view for the form library and would like to filter this view so only items whose "TargetUser" field matches current user's login ID are displayed.
I went to Edit View page to customize the view and tried to use the [Me] function but I got a "Filter value is not a valid text string" message instead when clicking OK. Apparently [Me] returns a Person/Group data type and the filter cannot compare its value
to that of "TargetUser".
I tried using text functions (ex: TEXT([Me],"") hoping to extract default string value from [Me]. The filter accepts the parameter without any error but the resulting fitlered list does not display any items at all.
I have googled this subject for hours but I have not found any solution.
It would be greatly appreciated if anyone can help me to create a functional filtered list.
FYI, my SharePoint 2007 installation is just WSS 3.0 + Form Server. I do not have MOSS 2007 (so no MOSS 2007 web parts or web services).
Thank you.
Jason

Here's what I usually do in order to accomplish this. Ultimately you'll need to have 2 different fields. There's the one you already have, with DOMAIN\username stored in it. Then you'll need an additional field as a "person" column type.
Call it "TargetPerson" or something.
Create a sharepoint designer workflow that runs each time an item is created or changed. One action:
Set FIELD to VALUE.
The first FIELD is "TargetPerson", the VALUE is your "TargetUser" field.
Once this is done, then the person value is stored in the person field. This is the field that you can filter by "TargetPerson" is equal to [Me]
Laura Rogers, MCSE, MCTS
SharePoint911: SharePoint Consulting
Blog: http://www.sharepoint911.com/blogs/laura
Twitter: WonderLaura

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