An isolation issue?

Hi,
The main instruments in my project are: a 6020E DAQ Pad and a pH meter. They are both hooked up to a laptop by usb interface. The pH meter keeps reading pH into LabVIEW program from a biochemical sample. Depending on conditions required, the LabVIEW program asks the DAQ Pad to output a certain analog voltage. The voltage is then converted to a current via a constant current source circuit (two-OP circuit) and the current is passing through the sample.
PH meter obtains pH valus by detecting potentials of acid concentration in hundred "mV" range. However, the pH meter always gets wrong pH values (out of measurement range) after that DAQ card is connected and turned on. I'm thinking this is happening due to "isolation issue" between two usb slots because it won't happen like this if I hook up DAQ and pH meter separately to two laptops. I wonder can I eliminate this issue by connecting an opto-isolator device, such as an "usb opto-isolator", to the pH meter instead of connecting to the laptop directly? I don't have quite understanding on this isolation issue. Can anyone give me a clue? Thanks in advance.
BTW, this problem also happens if the pH meter is connected by RS-232 interface.
Scottie

Hi Scottie,
To the best of my understanding (I developed electrodes, not the electronics, but I heard quite a lot from the guys who did the electronics), a shift in the two ground potentials can cause the A/D converter, because it's not isolated, to measure against the wrong ground. Ideally the reference electrode should form the "ground" for the A/D converter, but in a system where the pH input isn't isolated the ground and the reference electrode are often connected over a shunt resistor. In such a system, the real "ground" for the A/D converter is a wierd mix out of the reference electrode potential and the ground from the main supply (or battery if it's a bettery-driven meter). What happens then is that the "external" ground influences the "internal" ground over the shunt resistor and the signals shift. This is quite easy to imagine when you consider that the actual measuring circuit is a low-voltage high impedance circuit which is just begging to be corrupted.
The problem is basically a ground-loop where you end up shifting small currents through the reference electrode, thus changing the reference electrode potential. Because of the very small currents involved in pH measurements, it doesn't take much to have a big effect on the pH reading. Also, even passing small currents through the reference electrode will greatly shorten the lifetime of the reference electrode (The silver chloride will end up all being oxidised or reduced depending on which direction the current is flowing - a properly functioning reference electrode needs both metallic and reduced silver in immediate vicinity of the lead-off wire). Both problems will be solved by isolating the meter with an optically isolated RS232 connection.
It's truly an electronics problem. A properly isolated pH meter will not suffer from this problem (But they're expensinve of course). Simply sticking an RS232 optocoupler between the instrument and the computer usually does the job.
Shane.
PS
Do I understand that you are performing pH measurements in non-aqueous solutions? If so, make sure you're using the correct electrode for the job. Non-aqueous measurements are extremely difficult, and only the correct combination of electrode and meter will give correct results. This has a lot to do with the very high impedance of the solution which in turn greatly increases the impedance of the liquid junction of the reference electrode (Which a non-isolated, standard pH meter simply cannot handle). You then end up with a double high-impedance circuit. To get anything close to good readings (which is hard at the best of times in non-aqueous), you need a good meter AND a good electrode. I've published on this matter before. A sleeve-type reference electrode is really the only choice for non-aqueous measurements. Do a search for "Solvotrode" to see what an optimised non-aqueous pH-electrode looks like.
<\rant>Message Edited by shoneill on 03-01-2005 09:22 AM
Using LV 6.1 and 8.2.1 on W2k (SP4) and WXP (SP2)

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Transaction isolation issue in 6.1

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Thanks Seth.This works.
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          Regards,
          Rod
          "Seth White" <[email protected]> wrote in message
          news:[email protected]...
          >
          > Rod,
          >
          > Looks like there's a bug that won't let you specify 'Local' as the value
          for
          > method-intf. As a temporary workaround, you may want to leave out
          > the method-intf tag.
          >
          > Seth
          >
          > Rod Johnson wrote:
          >
          > > How do I specify tx isolation in WebLogic 6.1 for local entities?
          > >
          > > I've tried a stanza in weblogic-ejb-jar.xml like this:
          > >
          > > <transaction-isolation>
          > > <isolation-level>TRANSACTION_SERIALIZABLE</isolation-level>
          > > <method>
          > > <ejb-name>Seat</ejb-name>
          > > <method-intf>Local</method-intf>
          > > <method-name>*</method-name>
          > > </method>
          > > </transaction-isolation>
          > >
          > > I get the following error message from ejbc:
          > >
          > > ERROR: Error processing 'META-INF/weblogic-ejb-jar.xml':
          > > .weblogic-ejb-jar.transaction-isolation.method.method-intf. must be one
          of
          > > the values: home,Home,remote,Remote
          > >
          > > Does this mean I should use "Remote" for the method-intf (a bit
          strange)? Or
          > > isn't tx isolation control implemented in 6.1 for local entities?
          > >
          > > I've encountered this problem in 6.1 beta and the final release.
          > >
          > > Thanks,
          > > Rod
          >

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Cordian Support
@Cordianblog

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2.) When i opn the lid for the first time after a period of the mac being closed, i get a reasonable creak/crack from the left side of the screen hinge.
Is the opening range different from other ones in the store?
3.) When i run the battery down and it goes to sleep 'to preserve the contents of memory' it doesn't take long at all before battery so low it goes into deep sleep (ie state where all RAM contents are written to disk - and then takes a min or so to come to life again when you open the lid - my old macbook pro could last a good few hours in sleep mode before dying completely and deep sleeping
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Hi Greg,
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As can be seen in this forum (and a lot of other forums, as well), a lot of people are experiencing this problem on their 17" iMac G5 with iSight. Here are some pertinent details (which may be familiar to a lot of people but can be a primer for those who are just starting to experience the problem):
1. For most of us, these lines started appearing between 13-15 months after they purchased them. The lucky ones either had these failures occur during the first 12 months, or had APP.
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P.S. Suggestions that involve any sort of violence or industrial sabotage are not acceptable, please.
Note that Ale_Tog has put up a Flickr page where we can post photos of our poor iMacs. Just send the photo to [email protected] with the subject "Dead pixels on iMac". No text, just the photo attachment. (+Ale_Tog, if you read this, I hope you don't mind me posting this here. Also, I suggest that we at least put the first 5 chars of the serial number, the factory information which can be retrieved on the link in #2 above, and which country the unit is based.+). I highly recommend that everyone send a photo to show that these are not isolated issues.
To get an idea on how many people are experiencing this problem, here are a list of posts in these forums, as well as others, discussing this issue (feel free to add to this):
http://i7.ebayimg.com/05/i/000/b2/75/2e8d_1.JPG
http://i16.ebayimg.com/06/i/000/b2/75/2ee5_1.JPG
http://i12.ebayimg.com/07/i/000/b2/75/2faf_1.JPG
http://discussions.apple.com/thread.jspa?threadID=974094
http://discussions.apple.com/thread.jspa?messageID=5146382&tstart=0
http://www.macusersg.org/forums/index.php?topic=40998.0
http://discussions.apple.com/thread.jspa?threadID=607522&tstart=180
http://discussions.apple.com/thread.jspa?threadID=463075&tstart=270
http://discussions.apple.com/thread.jspa?threadID=197560&tstart=360 (this is about dead pixels, but one person reported a whole line)
http://discussions.apple.com/thread.jspa?threadID=292889&tstart=390
http://discussions.apple.com/thread.jspa?threadID=293895&tstart=390
http://discussions.apple.com/thread.jspa?threadID=279138&tstart=420
http://discussions.apple.com/thread.jspa?threadID=197630&tstart=465
http://discussions.apple.com/thread.jspa?threadID=197745&tstart=510
http://discussions.apple.com/thread.jspa?threadID=197741&tstart=510
http://discussions.apple.com/thread.jspa?threadID=197641&tstart=585
http://discussions.apple.com/thread.jspa?messageID=4227335&#4227335
http://discussions.apple.com/thread.jspa?messageID=976574&#976574
http://discussions.apple.com/messageview.jspa?messageID=4369582&stqc=true
http://discussions.apple.com/thread.jspa?threadID=778470&tstart=0
Please start sending your suggestions. The more the many-ier!

Yep. I feel Apple's 1 year manufacturer warranty for the iMac is not adequate, especially for an all-in-one unit with a relatively high price.
My iMac G5 started displaying a vertical cyan line about 4 weeks ago, only about 19-20 months after I bought it for Christmas in 2005.
I called up Apple to enquire what could be done and was told by their customer service that a rather long period had elasped since the warranty expired in 2006. So I was told to take the iMac to an authorised repair centre and Apple will not contribute to the cost of the repair.
I expect respectable service life from my computer and anything less than 5 years is totally unacceptable. Thus I seriously question the value proposition for the iMac in this respect. Does it mean that I have to replace my iMac every 2 years? The computer still feel reasonably zippy, I still have plenty of space left on my hard drive, but the screen is failing ...
Today another line (green) appeared on the screen ...
It is my understanding that a number of LCD monitor manufacturers are now providing 3 year warranties for their products. Now why should Apple only provide a 1 year warranty? Especially when the replacement option will cost more than buying an entire new LCD monitor with even better specifications?
Based on the number of responeses I have seen here, this is not a rare occurance and I seriously question their quality control in their manufacturing process. I think Apple should be responsible for these repairs, and also provide a 3-year warranty for their LCD screens.
My iMac's serial number is W8548Zxxxxx.
Sincerely yours, an unhappy Apple customer.

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After looking on the web, I realise this is not an isolated issue and many people have had it.
*Problem in bold if you cant be bothered reading everything :)*
The problem I have is with the touchpad on my Macbook Pro. This morning my mac had a funny turn and kept freezing soon after loading up the desktop. I could move around with the touchpad but not do much else, so I restarted and plugged in an external mouse and this worked. So I was really annoyed (My TV had decided it was going to pack in aswell this morn) and was about to hurl my mac at the TV to teach them both a lesson when my TV fixed itself and my touchpad gained some usability.
This is the strangest part - to start with the touchpad could double click - but you had to use three fingers instead of two, it could three finger swipe - but with four fingers and 5 fingers for expose!! But I couldn't single click. *Now, However, I can do everything on the mac by touching the pad but there is no response when I physically click the pad down. You can hear the click but nothing happens, unless you press really hard, in which case it works 1 out of 5 attempts.*
My macbook is only four months old, so I'm presuming it is still under warranty? However, I didn't buy directly from Apple but instead from Currys, will this make a difference. I would just take it in to an Apple Store but the nearest one is about 1.5 hours away and I have no car So I don't want to waste money and time getting there only for them to turn me away/ have no warranty!!
Thanks in advance for any help,
Adam

Should they fix it for free? I
If the unit is under a year old or you purchased the 3-year AppleCare plan, then yes.
Check your warranty status here.
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Graphics issues since latest 10.8.2 update

Last Friday, I applied the latest update to 10.8 (10.8.2?). Since then I have noticed a couple of issues, both of which appear to be graphics related. FWIW, my hardware is an early 2011, 15-inch MBP with discrete graphics (Radeon 6750M).
1. In one instance, I attached an external display to the Thunderbolt port (DVI adapter). The system switched to discrete graphics, and my onboard display suddenly had a very slight blue shade. The external display displayed color properly, only the onboard was affected. Unplugging the external display (and switching back to integrated graphics) fixed the onboard colors. Re-plugging the external yielded the same result. After a reboot, the issue has not re-occurred (~24hrs). Some searching of Google indicates that this is not an isolated issue. Is there a known cause (and solution), to prevent further interruptions?
2. In a number of occurances, I have seen the Terminal application become exremely slow to respond, as in 10+ second keypress responses. The entire application appears affected, including opening new terminal tabs and the cursor switching from I-beam to pointer (as I move it from the terminal space to the tab bar). After some amount of time (several minutes?), terminal function returns to normal. The system.log file shows the following message repeated during the event.
Oct 16 09:38:34 raar.example.com Terminal[242]: Unable to simultaneously satisfy constraints:
        "<NSLayoutConstraint:0x7fc50b6bbf10 H:[NSColorWell:0x7fc50b045800(28)]>",
        "<NSLayoutConstraint:0x7fc50b6b4ea0 H:[NSColorWell:0x7fc50b045800]-(NSSpace(8))-[NSTextField:0x7fc50b0435d0]>",
        "<NSLayoutConstraint:0x7fc50b6b3e20 NSButton:0x7fc50b6af140'Change\U2026'.leading == NSColorWell:0x7fc50b045800.leading>",
        "<NSLayoutConstraint:0x7fc50b6b4f00 H:[NSTextField:0x7fc50b0435d0]-(>=NSSpace(20))-|   (Names: '|':NSView:0x7fc50b041780 )>",
        "<NSLayoutConstraint:0x7fc50b6b3d00 H:[NSTextField:0x7fc50b6c1120]-(NSSpace(8))-[NSButton:0x7fc50b6af140'Change\U20 26']>",
        "<NSLayoutConstraint:0x7fc50b6bc9c0 H:[NSTextField:0x7fc50b6c1120(>=209)]>",
        "<NSLayoutConstraint:0x7fc50b6b31b0 H:|-(17)-[NSTextField:0x7fc50b6c1120]   (Names: '|':NSView:0x7fc50b041780 )>",
        "<NSAutoresizingMaskLayoutConstraint:0x7fc50cdc6d90 h=--& v=--& H:[NSView:0x7fc50b041780(0)]>"
    Will attempt to recover by breaking constraint
    <NSLayoutConstraint:0x7fc50b6bc9c0 H:[NSTextField:0x7fc50b6c1120(>=209)]>
    Set the NSUserDefault NSConstraintBasedLayoutVisualizeMutuallyExclusiveConstraints to YES to have -[NSWindow visualizeConstraints:] automatically called when this happens. And/or, break on objc_exception_throw to catch this in the debugger.

(1) is probably a colour profile bug. When you next see the issue, go to System Preferences > Displays > Colour, and confirm that the correct colour profile is selected for the affected monitor. If it is, then deselect it by choosing another one, then reselect it. If your display regains its expected colour you can assume it's a colour profile bug. In my experience colour profiles are prone to this kind of behaviour, though Apple has made things more stable in the last year or so.

Printing issues when printing to Server 2008 R2 Print Server

We have a problem with netwok printing that encompasses many different areas and versions of Windows OSes so I will be posting this in a few different places.
Let me lay this out for you. We have a single Server 2008 R2 print server with 300 printers of various models. This print server has both 32 and 64-bit drivers installed for every printer. For the HP printers we are using the HP Universal Printing PCL 6
(version 61.94.3.37) and for the Ricoh printers we are using their PCL6 driver for universal printing version 3.5. All drivers run in Isolation mode and no printer gets published to AD.
We have a mix of Windows clients printing to these printers, both XP Pro and Windows 7 32 and 64-bit.
Now for the problems: The other day one Isolation host on the server went crazy, processing was hitting 100% and memory was fluctuating and growing a lot. After investigating a little that isolation host was having issues accessing the Ricoh Driver (which
was 3.4 at the time). In an attempt to resolve the issue we updated the driver to V. 3.5. This seemed to fix the isolation issues and things calmed down however this is the beginning of many other issues for the clients. Both Windows OS versions (XP and 7)
don't seem to be either downloading and installing the updated driver and/or doing so correctly. Clients are now experiencing extremely slow printing, applications such as Word, Outlook, Excel and others open slowly and it can take 2-3 minutes for print dialog
boxes to open. In all cases it seems that we have to have a tech delete the printer(s), delete the driver and then re-install the printer to make things better but for some reason, which is really unknown, this process doesn't work for every machine and on
some we can't even remove the old drivers at all without booting into SafeMode and doing it that way.
With all of that said, are there any suggestions as to why the clients aren't downloading and installing the drivers from the server correctly? How to avoid these issues when we need to upgrade the drivers on the server in the future? Most importantly right
now, are there any recommendations or scripts on how to force the deletions of the printer, driver, reset the print spoolers and then re-add the printers in a more automated fashion?
I have played with both wmic, pnputil and printuidll and am trying to put something together but without a set solution that will work consistently it becomes a lot more difficult.

We are experiencing a very similar issue.
Windows Server 2008 R2. Printers are deployed over group policy.
Clients range from Windows 7 to Windows 8. Citrix XenDesktop and XenApp environment also connects to these endpoints.
We have A wide assortment of HP printers, and Ricoh Printers.
For the ricoh's we have been historically using the PCL6 drivers for the individual device type (not universal print). Up till recently, it all was working fine, until about some time in the middle of june, when everything just seemed to go crazy.
The issue was resolved by moving off from the PCL 6 drivers and using the PCL5e driver counterparts on all of our ricoh printers.
It would crash XenDesktop applications, it would crash office applications.
The print spooler would lock up, even if the ricoh printers were not actually used, just as long as they were loaded.
Even after loading PCL5 on the servers, some of the clients would simply not download the PCL5 version of the driver from the print server. In order to resolve this, I have created the steps below. Be advised, this may possibly cause damage on your system.
We just found it worked great for us. Local printers will likely have to be manually reinstalled after this.
Directions
Stop the print spooler
Open C:\Windows\System32\Spool and delete the following
All files in SERVERS
All files in PRINTERS
All files in drivers
All files in prtprocs
Start the print spooler
Open a command prompt as administrator, and run the following command
Cscript C:\windows\system32\Printing_Admin_Scripts\en-US\prndrvr.vbs -x
This should further delete all print drivers.
Open a command prompt as a standard user (not administrator) and run the following
Gpupdate
Now wait. It takes a while, but the printers will slowly start to repopulate.
I am still not sure what is going on with the PCL6 drivers for ricoh, and why this issue is happening. I'm guessing it has something to do with the Ricoh auto update that is included in their pcl6 drivers. Maybe some sort of auto update happened recently.

Setting Isolation Level In A UserTransaction

We are having a problem where a class creates a UserTransaction from the InitialContext,
but does not see any database changes made by other EJBs even though they have
been committed. This "seems" like an isolation issue.
What is the default isolation level for UserTransaction? And since it appears
that it is not seeing committed data, what level should it be set to? (i.e. TRANSACTION_READ_COMMITTED
would be nice...)

this is mirrored from the transaction newsgroup:
Joseph Weinstein <[email protected]> wrote:
>
>
Interesting, but it's not an isolation level issue. There is no DBMS
isolation level
that could cause a user not to see already-committed data.Well, we are using Oracle as our backend and it supports Read Uncommitted, Read
Committed and Serializable. The Serializable option would prevent a transaction
from seeing any committed data to a table (i.e. prevents unrepeatable reads).
The default isolation level of most DBMSes is READ_COMMITTED, and you
should
never have to change it, and you should be able to see already-committed
data.I agree, but that is not happening for us (and this gets somewhat complicated
with JMS). What is Weblogic 8.1's default isolation level for any transaction.
From the link below, I get the impression it is SERIALIZABLE which would explain
the behaviour I'm seeing. Athough the article seems to be talking about CMT (container
transation), I would suspect a BMT (bean managed transaction) be similar (just
manual).
If this only confuses things, please let me know the easiest way to communicate
this issue (code, etc..)
http://newsgroups.bea.com/cgi-bin/dnewsweb?cmd=article&group=weblogic.developer.interest.transaction&item=227&utag
(from the article)
Subject: Re: What is ths default transaction isolation level
Date: Mon, 12 Feb 2001 15:27:24 -0500
From: "Cameron Purdy" <[email protected]>
Organization: BEA SYSTEMS Inc
Newsgroup: weblogic.developer.interest.transaction
serializable
-- Cameron Purdy Tangosol, Inc. http://www.tangosol.com +1.617.623.5782 WebLogic
Consulting Available
"mrityunjay" <[email protected]> wrote in message news:3a86c781$[email protected]..
Hi , > If transaction isolation , for a EJB is not specified what is the > defaulttransaction isolation level > Thanks > Jay > >

Macbook Pro Early 2011 Display issue

Hi all,
After reading the replacement program that has been extended to MBP for 15" and 17", is there going to be any news with regards to the 13"?
The reason why I'm asking is that while I'm not sure if mine is an isolated issue or widespread/common occurrence, I have had my logic board replaced last year due to a display issue, and currently still unable to run external display, despite reading up on discussion that is going on.
The symptoms mirror that of the 15"/17", just that the 13" does not have a dedicated GPU.
Hope to get more suggestions/ solutions/ news to potential replacement program from here.
Thanks all!
Regards,
Ziang

Welcome to Apple Support Communities
Early 2011 15 and 17-inch MacBooks Pro have had several GPU issues that causes graphic corruption, and it was an issue that showed in most MacBooks Pro. However, this does not apply to the 13-inch MacBook Pro, so I think it is just an issue that has appeared on your Mac but there is not a reason for a replacement program.

An isolation issue?

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