Removing 50Hz interference signal

Hello,
I am using a digital multimeter to measure a transient potential. The problem is that I see 50Hz interference which has a larger amplitude than the useful signal I need to acquire.
I was thinking over a digital filter to filter out this interference but this is not clear to me. Looking at signal processing palette, I know there are several filters, but I am afraid some filters can affect my interest signal.
Is it possible to remove only this 50 Hz interference signal without loosing information from other bands of the spectrum?
Thanks in advance,
Marc

Marc,
Yes. No. Maybe. More information is needed to select an answer which has some validity for your application.
First, It is always better to keep the interference from getting into your data rather than trying to filter it out later. A differential amplifier before the multimeter might help. Check your grounding to make sure that a ground loop is not introducing the interference.
How large is the interfering signal? How large are the largest and smallest desired signals? What spectral bands contain information important to your process? What is the sampling rate? Is the interfering signal sinusoidal or a complex waveform? How much interference can you tolerate?
Lynn

Similar Messages

Want to input interference signal in labview + perform bandpass filtering/demodulation

Hello to whom it may concern,
I have a fiber-based OCT system linked to a Tektronix TDS 2024B digital oscilloscope, with which is showing the interference fringes of the low-coherence lightsource. The signal is linked to the computer using the NI DAQ Board USB-6251. I want to input the fringes using Labview and not only that, but to perform a high-pass filter command, along with an active full-wave rectifier and a lowpass filter to see the group velocity of the interference pulse. Now I am new to using Labview so this question be a little elementary, however I am struggling here. Any helps are greatly appreciated.

Hello!
Basically you will need to measure a signal in LabVIEW and then perform some processing on it. First I suggest, if you haven’t, getting familiar to LabVIEW and DAQmx that are basically what you will use for acquisition. For processing, you might find useful some toolkits we have for filters and signal processing. I’m linking information on these subjects, if you wish, you can download them in evaluation mode and take a look at the examples on how to use those functions.
NI LabVIEW Digital Filter Design Toolkit
NI LabVIEW Advanced Signal Processing Toolkit
Getting Started with NI-DAQmx
Getting Started with LabVIEW
Regards,
Alina M

50 Hz interference PCI 4070 DMM

Hello,
I am using a PCI 4070 DMM to measure a waveform voltage in a range of 200 mV at 1 kS/s. The point is that I see 50Hz interference which is higher than the useful signal I need to acquire.
As I learnt from the DMMs Help file:
Note When using a resolution of 6.5 digits on the NI 4065 and NI 4070/4071/4072, 50 Hz and 60 Hz noise will be rejected automatically. This is due to the selection of default aperture times on the devices, which appropriately filter out noise.
Since I set sample rate at 1 kS/s, 50 Hz noise is not rejected automatically; I tried configuring powerline frequency at 50 Hz but the problem remains, so I would like to know how I can filter out noise. Maybe adjusting aperture time or other parameters in a properly way?
If it’s not possible through DMMs measurement configuration, should I turn to signal processing tools?
Thanks,
Marc

Hi Marc,
What type of signal are you measuring, how high is the frequency content of interest? Are you getting an effective sample rate of 1kS/s or are you configuring an aperture of 1ms?
Here is a link that better describes the DMM measurement cycle (http://zone.ni.com/reference/en-XX/help/370384N-01/dmm/measurement_cycle/). I wanted to be sure you were aware of all of the parameters that affect the effective reading rate of the DMM.
Your DMM bandwidth, assuming a 1ms aperture time, is wide enough to measure the 50Hz interference. If you increased the aperture time for the DMM you would reduce that bandwidth and begin reducing the amplitude of the interference. (http://zone.ni.com/reference/en-XX/help/370384N-01/dmm/dc_noise_rejection/). The best rejection is achieved when your aperture time is configured to be at 1 PLC, however this will result in less bandwidth for you measurement.
If your signal of interest requires you to have an aperture time of 1ms, you could post process the data with some filtering.
Steve B

How can I get the peak and valley of a MZI signal

I am using MZI signal which is similar to sine wave with frequency of 10MHz to calibrate an interference signal. I want to get the peak and valley of the MZI signal and get the corresponding value of interference signal at the same location. The problem is that the MZI signal aquired by DAQ is not smooth, Please see attached filter.PNG, the top left is the MZI, top right is the MZI Zoomed in, you can see that there may be two values that are approximately same to each other. I used a peak detector to detect both the peak and valley and a build array to concatenate them. I am worried that the peak detector may find two peaks or two valleys in a fringe. So I used the filter function in express to bandpass the MZI signal (cutoff frequency is 8MHZ~12MHZ) to smooth the signal, the result zoomed in is the bottom graph in filter.PNG. But I found that it did not solve the problem but cause phase shift. Is there somebody can give some help?
Attachments:
filter.PNG ‏143 KB
peak detector.PNG ‏69 KB

I don't know anything about MZI signals, but I do know sine waves. If this is a sine wave, it is relatively easy to measure its amplitude as long as you know the frequency. Since you say it is 10 MHz, you appear to know the frequency. You can use Fourier analysis to determine the magnitude and phase of your signal, as long is it is a steady signal that doesn't change frequency or amplitude.
Generate a sine and cosine wave using the same frequency. Divide each wave by the sum of its points. Multiply each one by your incoming signal and sum all the values, one sum for sine and one sum for cosine. The sums should be the coefficients of the sine and cosine components of your unknown signal. The ratio tells you the phase of the signal. If you multiply the sine and cosine waves by their coefficients and add them together, you should be very close to your incoming signal. The amplitude of your signal is equal to square root of A*A+B*B, where A and B are your coefficients.
I may be off by a constant factor here somewhere (probably pi), since I didn't write down the equations and verify them. These equations are the basis of the Fourier series, though, so they would be fairly easy to find.
Another option would be resampling. If you upsampled the data and increased the data resolution by a factor of 10 or so and filtered the results using an FIR filter, you would have a much cleaner signal with a lot more detail. You wouldn't have any problem locating and measuring peaks and valleys. This would probably work better with your data, since it looks like it doesn't have a constant magnitude. To upsample the data, just add 9 zeroes between each data point. Create a lowpass FIR filter that is based on 10 times the original sampling frequency and has an amplitude of 10. The cutoff frequency should be half the original sampling rate. Filter your new data and you should get the same waveform with 10 times the resolution.
Bruce
Message Edited by Bruce Ammons on 10-02-2008 09:10 PM
Bruce Ammons
Ammons Engineering

How to remove roll bars from a television on a video in after effects?

I have footage with a person talking in front of a television and It has roll bars scrolling down on it.
Is there a way to remove this interference?

Simply mask out everything and replace the whole screen content.
Mylenium

How lab view can be used for signal analysis of hf signals recrded in field

im interested in using labview tool to analyse hf signals in terms of removing noise ,amplipying signal strand identify modulation schemes used

The kind of things you mention are certainly within LV's capabilities. When you say "HF" what frequencies do you mean?
Mike...
Certified Professional Instructor
Certified LabVIEW Architect
LabVIEW Champion
"... after all, He's not a tame lion..."
Be thinking ahead and mark your dance card for NI Week 2015 now: TS 6139 - Object Oriented First Steps

Difference between CU, Noise and Interference

Hello everyone,
I just dug myself into a hole. We have Cisco Prime 2.0 installed with a handful of 5508 WLCs. I am trying to troubleshoot issues with client's losing connectivity. And I have found AP's with high channel utilization but low interfence and zero clients associated. Then I found AP's that have passed the Noise Profile but failed the Interference Profile. I am getting to confused as to what these all mean. I read definitions on each and its all jumbling together.
From what I thought, this is what each means:
CU - traffic the radio can understand that's not being generated by itself or clients associated.
Interference - signals on the same channel
Noise - signals on the same channel that are not understood at all by radio
Can someone explain in layman's terms what the difference is between channel utilization, interference and noise?
Also, any tips on useful Prime alarms for monitoring a wireless network would be helpful as well.
Thanks everyone and happy holidays!

In regards to your clients loosing connectivity, you need to do basic troubleshooting.
1. Determine the signal strength of the SSID by looking at the client. You also need to verify the signal strength from the view of the WLC.
2. How about the client's wireless NIC drivers? Are they updated?
3. Is this issue observed with other clients or just one client?
4. Is this issue affecting similar clients, i. e. all Android, Apple, Windows, Intel chips, etc.
5. What is the location of the client vs the nearest AP?
6 What is the location of the client vs the AP the client is currently associated to?
Sent from Cisco Technical Support Nintendo App

I am desperate!! slow choppy network speeds (not actual inability to cnnct)

I have a 13" macbook air that has the following problem: I can connect to wifi networks (including at home WPA and also tried WPA2 settings) but even though I may get proper speed at first, I soon lose that and it becomes much slower and choppy (if I open activity monitor I can see the speed going up and down like crazy...). My internet speed at home is 12mpbs set by my provider. When I perform speed tests (vis speedtest.net or downloading files from other speed test sites) on my windows PC that is also on this network I get the full download speed. However with this MAC while I initially did get the full speed, it is now down to an average of 3-5mbps and the activity monitor, again, shows choppy behavior so it will be at 8 then at zero almost and then up and down again but never near the full speed. I tried to connect to other networks and I have the same problem - once this happens it stays. I tried removing the airport connection in network preferences and adding it again it does not help.
I TALKED TO APPLE AND HAD MY COMPUTER TESTED BY THEM - they didn't find any hardware issues (they said it was fine - but it isn't) but they still replaced the airport hardware in the computer - both the chip and the antenna (which meant replacing the entire screen). I brought the computer home, ran a speed test and everything was fine. I thought GREAT but then something happened and the problem returned. What I did (which I think was unrelated) was connect via SMB to a PC at home and I tried to stream a movie file. I noticed it kept 'pausing' so I opened up activity monitor again and to my HORROR I saw the choppy wave with network speed very inconsistent going up and down like crazy... I tried connecting to my slingox using the sling web access after disconnecting from my home PC but got partial speed and lots of drops too. I tried the speed test again multiple times, nothing seems to work.
SO I don't know what to do at this point. I have 10.6.6 running. I heard something about a firmware update but I am new to mac so not sure how to even do that or what else I can do to solve this problem or what is causing it. BTW - logging in now from the guest account still does not fix the issues and they remain the same.
I am desperately looking for help!!
Thanks a lot!

Have you been able to reproduce your problems on other wireless networks other than at your house? It appears you are saying that this occurs on all wireless, but I'm not sure from your comment. If it's only at home, it would appear to be a compatibility issue between your wireless access point and the Macbook Air, which isn't uncommon. Sometimes a firmware upgrade to the access point can fix it, sometimes it might require switching to a different brand of access point. It would be great if you could borrow (or buy and return) a different access point/router to test. An Apple airport would be the best to use of course. Not the easiest solution, but lets you help rule out a hardware issue with your air.
My isp provides 15mbps but my wireless devices such as my iphone, ipad, laptop usually only get 6.5-8 mbps when testing speeds to the internet. I don't expect it to be as good as the wired due to interference, signal, etc. I don't get the choppy behavior however. Firware updates from Apple will appear in the same manner as standard software updates. If there is one available for your system it should appear when you check for software updates. That being said, I believe you can also manually download them from the Apple site.

Apple TV a new paradigm

My Apple TV does what it says it does and is useful. However I think it is a miss. I also have my Powerbook hooked up directly to a projector and using a wireless keyboard and mouse. I looked over the back shelf in the theater where the projector sits. I had a DVR, a Direct TV HD receiver, a 4 way HDMI switch, a Playstation 2 and an Apple TV, a mixboard and a sound line switch. The DVR is redundant with the laptop drive. I will limit my HDTV watching to watching a window driven by my Escape "myTVPVR" and I know it can only use S video as HD content is blocked outside of the satellite receiver. The HDMI switch seems to be incompatable and looks scrambled when trying to pass a signal. All these components and cables and switches plus a sound system requiring a preamp, scaler, and more switches are only there because the general purpose computer that could be doing all of the sound conditioning, scaling, conversion, dvd playing, recording, burning, sound and video switching, scheduling, is being factored out of the architecture of what should really be a home network server using the home theater as its foundation. With this set up and Leopard to manage multiple spaces on multiple screens using a bluetooth mouse and keyboard as the ultimate "remote" and the ability to go to a webpage and zoom the projector screen onto a small web video window to fill the screen. If you make a spreadsheet of the costs involved for dedicated components versus a full computer centric architecture, you immediately see that it is cheaper to do the computer centric architecture which doubles as the home server to which you also attach a large hard drive, printer, scanner. Cost are further reduced if you implement "network-over-power line". That solves the problem of distributing bandwidth throughout the home without signal drop or interference and better security. A brilliant move for Apple would be to make a "Wii" remote pointer device and use it to control the screen cursor. You could call this the "couch mouse", has a nice ring to it. This would allow control of the full OS X GUI or an icon based program like "Front Row". The cost of good sound would be greatly lowered if, say Bose, made a line of speakers with a built in power amp tailored exactly to the drivers, which get their channel sent to them via the power line network signal. This is an instant multi-room, multi-channel sound system which currently requires expensive dedicated components. Apple need to educate the public that this is what they need and that home networking is now simple enough for non-IT types. The campaign would have the slogan: "It's time to bring the network home".

This is a rework and clarification of my original post that opened this topic.
The Apple TV needs to be transformed from a separate appliance to become a powerful general pupose home server. The "digital hub" done right and for real.
It would take the form of an enhanced Mac Mini with all the ports, WiFi N, Bluetooth, Express card slot and GPU found on a MacBook pro, adding HDMI 1.3 output and input as well as adding a dedicated converter with component and S video in. There would be a matching, separate optical drive so you could roll with the punches on the format wars.
As the home server, home theater functionality is only one node.
Nothing in the above requires any dramatic change to existing hardware and software, however three innovations would "knock the ball out of the park".
1. Control a screen cursor with a "Wii"-like controler. Call it the "Air Mouse" or "Couch Mouse. It would have a scroll ball and 4 buttons like the Mighty Mouse. Make it possible to have several of these devices independently move different unique cursors with their own icon. I'll leave the gaming possibilities to your imagination. Pair this with the existing Bluetooth keyboard but enhance it with LED backlighting that times out after the last touch.
2. Implement the home network as "signal-over-power-line". This could provide higher bandwidth throughout the house without interference, signal loss, with less range away from the house as a security point. This new network-over-the-power-lines would obviously be built-in to the "Super Mac Mini" server described above. Any device is on the network simply by plugging it in for power. A "paper station" for a scanner and printer could be placed anywhere. A power-line-signal to WiFi converter brick could be placed in any room to tie in MacBooks and iPhones.
3. Build or partner with Bose to build home theater speakers with built in power amps tailored to optimize the driver/enclosure. When it's plugged in it takes its signal from the power line network per #2 above. A power-brick sized converter could change the network signal to an analog feed for any speaker that doesn't have this feature built-in. Typical 5.1 or 7.1 signal wire clutter and welding cable speaker wire would be a thing of the past.
It would be ideal if projectors and large monitors were compliant with the 1920 x 1200 resolution common to computers or at least give a choice of resolution within OS X at the more common "TV" resolution of 1280 x 768 or 1920 x 1080. Right now OS X will not scale exactly to a "TV" display.
Backup would be through a central drive on the power line network and "Time Machine" should be fixed to work with central network storage and enable backup to multiple clients.
With this architecture any ad hoc node in the network can stream or store audio, video and text and control home security and automation if authorized.
It should be pointed out also that with this architecture, the "TV" large screen, and Mac Mini Server can be placed on a rolling A/V cart and moved anywhere in the house and set up merely by plugging in one power cord. Any tie-in to a cable or satellite box is done with an adapter feeding it to the power line network.
The trick here is to make home networking so simple, intuitive, standardized, accessible that the consumer experiences the ease of an iPhone.
This would have to be introduced with advertising similar to the 1984 Mac TV spot and infomercials that demonstrate how easy this all is. It would show a huge garage sale for all the discrete devices and cables you could now remove. It would show a breakdown of the system cost for the server components versus the discrete component costs and emphasize that this system provides the home theater, home computer, and expands easily to include home security and automation.
Obviously this network expands by adding iMacs, iPhones, Macbooks as ad hoc network nodes. Perhaps some elements of OS X Server would appear in plain vanilla OS X automating through icon based diagrams with each icon representing a node and that icon right clickable to adjust settings.
The current pile of remotes for each component are banished forever. The theoretical universal remote control becomes a reality.
The catch phrase of the campaign could be; "It's time to bring the network home".

Reliable internet in Time Capsule

Hello,
I'm sure I'm not the first person to write about this as I've been reading through many other posts and a plethora of alternatives. However, I am always open for other ideas and opinions, so if any of you would like to share some theories and ideas for a fix, I would be much appreciative!
I have had my MBP for 1.5 years and have had consistent problems with it. It finally got so bad a couple of weeks ago that I purchased a Time Capsule because I wanted to save my data in case the computer completely croaked. I had a terrible time getting Time Capsule to work. Internet has always been wonky on this machine. It has a difficult time connecting to my University's WLAN and has always had terrible receiving strength. The Apple authorized service center here told me it's due to the metal casing of the MBP and an unfortunate fact of life. So I was expecting some issues with TC as I would occasionally have problems with my AirPort Extreme. The initial backup took nearly all night (and not because of the size of the backup, but because it would get 600 MB into backing up and then freeze/stall out, and then fail). I was able to finally get a complete backup by taking my MBP, putting it on the computer chair, and literally wheeling it in front of the base station (a distance of less than 2 feet). Then it worked.
I went through the Troubleshooting of the TC booklet and tried very hard to remove any interference factor. There's no cordless phone. It's on a wooden bookcase. No cords near it. It's located in a central location, and my laptop is rarely more than 15 feet away from it. Most of the time, it's less than 5 feet away. I even went and got iStumbler and was able to see about a 85-90% signal strength, with 9% noise, and it was not adjacent to the channels of the other wireless networks in my apartment complex. Yet, as it is, I am able to get online with the TC, it will last for approximately 10 seconds, and then the internet stalls out. TC stays green, signal strength is at maximum bars, yet no internet. Safari will say "Unable to open webpage because of no internet" and will ask to do a Network Diagnostic test. If I click on it, it shows Airport, Airport Settings, and Network Settings as being green. ISP, Internet, and Server are red. It will go through the diagnostic process and about 10 seconds later, will say "Your internet is configured correctly and working properly." Then if I close out of that, go to Safari, my internet is magically working again! ... For 10 seconds. Then I get the Network Diagnostic tool, and this becomes a cycle that goes into perpetuity and becomes very, very frustrating.
I called AppleCare about my other computer issues (dead black screen, wonky keyboard, weird AirPort issues with TC, randomly shutting down, etc.) They recommended a logic board replacement. So I sent it in for service and got it back Thursday with a new logic board. It still displays some weird symptoms, but the AirPort/TC issue is still just as terrible as ever. Even worse, it wouldn't back up at all, it would instantly fail. Called AppleCare again, went through creating a new user to see if the problem replicated there (it did), and was then transferred to a very helpful guy in the Wireless group who had me go through, delete all my preference files for networking/TC in the library, restart, and re-create a wireless network. It worked BEAUTIFULLY. It did another backup, and this time it did another complete backup. It took 5 hours and worked without a hitch. Went to bed last night and put the computer in sleep mode.
Woke up this morning... and we're back to Square One. I get 10 seconds of internet and that's it. I finally got so fed up that I'm now using ethernet because I cannot, for the life of me, get Time Capsule to work. I went through and removed all network preferences again, restored the TC to factory settings, and get 10 seconds of internet time before it croaks. If I turn AirPort off, then turn it back on, it automatically rejoins my TC network and internet works... for 10 seconds.
Called AppleCare again, did a hardware test, and everything shows as normal (even though my computer still shuts off randomly). Was told to try and see how it connects to other networks (it's mostly fine, but signal strength is weak as usual, and drops off a lot, mostly due to the metal casing I'm assuming). Was told that the logic board might need re-replacing to see if it comes with a stronger "System Management Controller" that could send more power to the AirPort card or a new AirPort card or both.
Sorry for this long melodrama! I hope I've explained it well enough that someone might know of something I have missed. I'm really not wanting to call AppleCare again, I'm sure they're tired of hearing me. I've had enough issues with my MBP, without having to add the Time Capsule to the mix. I'm hoping it's something minor.

Talked again with AppleCare... they think my TC needs replacement.

Filtering an impedance measurement

Hello,
I am in the process of developing a bio-impedance measurement system: we are using an external stimulation signal (of known amplitude, frequency and phase) and measure two pressure signals (the impedance is calculated from these). However, the heart acts sort of as a secondary stimulator, which puts an unwanted interference in our signal. The problem is, that the heart's frequency is right in the range of our stimulating signal, so we cannot use a simple high/low-pass filter, plus the heart's frequency and amplitude changes a bit in time. This interference is sometimes tolerable and does not bother the analysis, while sometimes it makes analysis nearly impossible.
Can we get rid of this secondary component from our signals? We have the blood pressure data recorded, which correlates with the heart's activity and I guess this might be some starting point for the filtering. What should I do? (I have no expertise with filtering, unfortunately).
Thanks very much
Engage! using LV2012

Thanks for looking into it.
Here I attach a rough image of our setup: we have the stimulator to create a pressure signal, p2 is right at this stimulator (abount an inch further), while p1 is further from it (about an inch from the subject). The stimulator is attached to the subject via a tube, and the pressure transducers are sampling from the inside of the tube.
1. This I guess explains, why P2 is so similar to the original.
2. I think, the last column is not actual data.
3. We are using an NI-6211, so I guess we can get to higher sampling rates. However, previously we have used 128 or 256 Hz for quite a long time and they were more or less fine, although we did not try automatically removing heart interference. How high should I go? We are now working on 3-4 channels, however we plan to include some more channels, not more than 8 (with differential reading).
4. Ok, I'll loop back the AO to an AI. (Or can I somehow read it back from software? I am using a continuous generation based on NI cont. generation example)
5. That's right, I want to suppress heart-related components.
6. Right now I do not know exactly, however as I have some new subjects, I'll try to get some measurements with no heart as well. (although it will be two separate files: one with heart present and another one without heart)
7. We only need impedance at frequency components of the stimulation signal, and we need the complex impedance (however not as mag/phase, but re/im, but I guess it's marginal)
8. Yes, rats.
Actually, if you think it's better, we can get ECG instead of the blood pressure, however I think that blood pressure might correlate more with our interference.
Engage! using LV2012

Extending an extreme dual band network using an old Express (802.11g)s

Previously I had a 802.11g home network based on two Airport Express (old version) in WDS mode.
I've installed a new Airport extreme station in order to have a dual-band network to use 802.11g/n without loosing performance and hoping to cover my area with the enhanced power.
Unfortunately there are still some corners with insufficient signal so i tried to extend the 802.11g segment with the old airport, checking the extreme flag to allow the network to be expanded and manually configuring the express WDS page.
I payed attention to the channel (the same in extreme and express station) and configured the airport ID of the extreme base station in the express remote station.

When using WDS you automatically reduce the efficiency of the Airport Extreme's 802.11n extended features. WDS requires that the network drops to 802.11g instead of 802.11n which boasts the extended network range.
There isn't much more you could do for network range other than changing the channel to remove wireless interference or move the Airport Expresses closer to the areas of low signal (internet speed will be reduced the farther the Expresses are from the main base.)

Very low frequency caused by sample frequency in FFT analog input?

I'm measuring a very low frequency on my analog input, this frequency is in connection with the sample frequency of the Analog Input. At a sample frequency of 1000Hz I see a frequency of 0,05Hz in my FFT, at a sample frequency of 500Hz I see a frequency of 0,02Hz.
Attached is a screenshot of an example how I see this very low frequency.
My hardware: NI USB 6008 --> measuring on AI-0 (in this example the input is unwired). But in my real measurement I see the same FFT + signals I want to see (about 2 Hz).
In my real measurement I windowed the FFT (1-3Hz) so I see only the FFT I want to see. But I suspect that my complete signal moves along with this very low frequency of 0,05Hz. I saw this in my measerement.
What did I do wrong?
Attachments:
screenshot.JPG ‏66 KB

First, do you live in Europe? If so, that 50Hz could be power-line pick up.
Antialias filtering must be done in hardware before the DAQ. Because of the way aliasing works if you have sampled the signal it's already too late, you're hosed and no amount of digital filtering can remove the aliased signal. In terms of filter specifications, the filter cutoff needs to be at twice the highest frequency you are interested in seeing. For example, if you are looking for signals in the 2- to 5-Hz range, your antialiasing filter should cutoff at around 10Hz.
Obviously good signal management is also needed: shielding, appropriate signal termination, proper lead dress and spacing from known noise sources, etc...
Mike...
PS: There were no attachments to your last post.
Certified Professional Instructor
Certified LabVIEW Architect
LabVIEW Champion
"... after all, He's not a tame lion..."
Be thinking ahead and mark your dance card for NI Week 2015 now: TS 6139 - Object Oriented First Steps

Shield continuity with CB-68-LPR

I have an open-ended shielded cable coming from the amplifier of a force sensor. The cable
contains 6 twisted and shield differential channel, 5V, 0V, and AGND. I have screwed the
open-ended side to the CB-68-LPR terminal which is it-self connected to a 6034-Series E
multifunction card by means of the SH-68-68-EP shielded cable.
sensor------>amplifier------>CB-68-LPR------->6034.
I see that I am picking up lot of interference (50 Hz but also other stuff
like a strong but intermittent  26 Hz signal which I have not yet identified).
I succeeded reducing somewhat 50Hz interference by moving the power line of the PC
but I think that I have another problem with the fact that the shield of the open-ended cable
is connected to nothing. As a matter of fact, it seems that connecting the shielding of the
connecting cable with the connector of the CB-68-LPR helps.
My question is what is  the best way connecting this shielding to the CB-68-LPR terminal
or to SH-68-68-EP to have continuity?
I would also appreciate any other suggestions. Regards,
Gabriel
PS: I don't have problem when I connect directly the sensor to the 6034-E.

I have a cable very similar to the SH-68-68-EP but with one open end that connects
the amplifier of my 6DOF force/torque sensor (Nano 17, ATI technology). As said in my previous
post, I have screwed to wires of the open-ended side to a CB-68-LPR terminal which is it-self
connected to a 6034-Series E multifunction card by means of the SH-68-68-EP.
[F/T sensor] ==> [preamplifier] ==(shielded open-ended cable)==>[CB-68-LPR]==(SH-68-68-EP)==>[6034E]
I have seen that it is good practive to avoid grounding shield of the cable on both sides to avoid ground loop
currents (NI Tutorial: http://zone.ni.com/devzone/cda/tut/p/id/3344). In this document, Figure 18
shows that the shield should be grounded on the signal source side.
In my case, the amplifier fo the force/torque sensor does not have any alimentation but is, I guess,
powered-on by the 5V-DGND coming from the PC through 6034E cards. I don't see any way
to ground it on the signal source side.
The question is what would be good practice with respect to the shield of the open-ended cable?
Should I try to connect it with the shield of the the SH-68-68-EP?
If so, how ? (I have the CB-68-LPR screw terminal in the middle)
Thank you.
Message Edited by gavril on 10-23-2006 05:48 AM

Loss of internet connection only at weekends

Hi,
Recently, my HH1 has been losing connection to the Internet on Saturdays. The S/N margin in the HH Manager is about 0.5. Restarting the HH restores connection to the Internet and sets the S/N margin to a normal value.
Why does this happen, and why should it happen only at weekends?
Thank you and best wishes.

Hi,
I have posted the btspeedchecker results and my HH settings below. The S/N margin drops to about 0.5 at weekends.
I used to have the Hub connected to our telephone extension socket. I recently connected it to the main telephone socket (where it is now) and that doubled my download speed. The telephone is still plugged (via a Netgear filter) into the extension socket. The line is quiet. I was getting some interference from the telephone cable to my broadband connection. The Netgear filter (but strangely no other filter) removed the interference.
Thank you and best wishes.
1. Best Effort Test: -provides background information.
Download Speed
1.25 Mbps
0 Mbps
2 Mbps
Max Achievable Speed
Download speedachieved during the test was - 1.25 Mbps
For your connection, the acceptable range of speeds is 0.8 Mbps-2 Mbps.
IP Profile for your line is - 1.27 Mbps
2. Upstream Test: -provides background information.
Upload Speed
0.34 Mbps
0 Mbps
0.45 Mbps
Max Achievable Speed
Upload speed achieved during the test was - 0.34Mbps
Additional Information:
Upstream Rate IP profile on your line is - 0.45 Mbps
Link Information
Uptime:
2 days, 1:02:56
Modulation:
G.992.1 annex A
Bandwidth (Up/Down) [kbps/kbps]:
448 / 1,440
Data Transferred (Sent/Received) [MB/GB]:
91.98 / 1.62
Output Power (Up/Down) [dBm]:
12.5 / 16.0
Line Attenuation (Up/Down) [dB]:
31.5 / 63.5
SN Margin (Up/Down) [dB]:
10.0 / 8.0
Vendor ID (Local/Remote):
TMMB / IFTN
Loss of Framing (Local/Remote):
0 / 0
Loss of Signal (Local/Remote):
21 / 0
Loss of Power (Local/Remote):
0 / 0
Loss of Link (Remote):
0
Error Seconds (Local/Remote):
58 / 0
FEC Errors (Up/Down):
0 / 95,550
CRC Errors (Up/Down):
0 / 5,316
HEC Errors (Up/Down):
0 / 4,463
Line Profile:
Interleaved

Removing 50Hz interference signal

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