Speed measurement with PCI6601

I am building an application for measuring two linear encoders ( micrometers ) and one quadrature encoder for measuring speed of one motor.
At the moment I can read the two linear encoders with the "position measurement" option for the PCI6601.
But I have trouble to calculate in an easy way the speed of the rotating motor in RPM.
Could anyone have any easy solution for doing this?
Thanks
Massimo Visintin

Massimo,
A few notes in no particular order:
1. Re: future use of last counter for another speed measurement. With the 6601, you only have 1 DMA channel available for buffered measurements. A second buffered measurement would have to be manually configured to use interrupts.
A buffered measurement will give you much better precision, but you may be better off starting with a simpler unbuffered approach when getting started.
2. How accurately do you need to measure speed? And how often do you need a new measurement? It sounds like you're reasonably happy with a simple speed estimate made about once per second.
3. Have you considered making a separate loop for the speed measurement? You could simply read the count once per second (unbuffered) and put it into a shift register. Then estimate speed as delta counts divided by delta time. A small enhancement would be to also store the time from 'Tick Count (msec)' on each loop, and use a measured delta time rather than an assumed one in the calculation.
Note that with this method, it's best to run unbuffered to avoid the lock-up problem you saw. It'll also be simpler to add your second speed-measurement counter task in the future.
4. Again, there *are* solutions available involving precise buffered measurements. I recently posted a DAQmx-based example that includes an instant-response buffered read (toward the end of this thread.). But I'd recommend first getting a simpler approach to work, then coming back to the buffered measurements later when you're sure you need more precision.
Good luck!
-Kevin P.

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Hello Mateusz. Thank you for responding me.
You can see my signal taken from scope and check my vi file. Noise causes regulator of the motor I drive. If regulator is switched off there is no noise and if I turn my motor by hand, I get correct values of velocity, but when I turn on the controller, I get full of noise in my signal, so DAQ card reads all those noise as many signals, so it displys velocity much greater than it's real. I moved my daq card away from controller as much as possible and used coaxial cable, but noise still appear. I hope you have any idea.
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Attachments:
DAQmx velocity.vi ‏45 KB
scope_0.JPG ‏118 KB

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I'm going to copy/paste your pdf into the thread to make things easier to read:
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Hello,
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Attachments:
FetchinChunks.jpg ‏181 KB

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How to use external timebase for Two Edge Separation measurement with PCIe 6351

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Hello,
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Samples Not Acquired on NI 660x or NI 6624 Devices When using pulse width, semi-period or two-edge separation buffered measurements with the NI 660x and NI 6624 on counters 0 and 1, some samples may not be acquired under certain circumstances.

In the DAQmx 9.4 Readme the following is stated:
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Are there any NI Product Support Engineers out there who has an answer to this question and who are willing to share it with me?

Personal recruitment How to do new measure with function call Update IT4000

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Andy Goris wrote:
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Exporting set of measures with aliases into essbase cube

We were wandering if there is an easy way to import bunch of measures with aliases into Essbase cube rather then entering them one by one?
thank you

Simplest way, would be to create a spreadsheet with the Measures and alias listed in column format.
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Speed issue with TC and Airport Express 802.11n in WDS mode...

Here is my problem.
I replaced my older base station / Express duo with
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When I check the wireless clients from the TC, I find my iMac running at 130Mbits and the Extreme at 54Mbits.
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And, why does my iMac connect with 130 and not with 300Mbits?
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Instead of using WDS, you should take advantage of the "Allow this network to be extended" option that is available for the 802.11n AirPorts including the TC. WDS only operates in the 802.11g radio mode.
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(ref: Page 46 of "Designing AirPort Networks Using AirPort Utility).

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Hi,
While running user measurement with USMM I am getting following run
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Ae per Note - 1230640 :- You call transaction USMM and want to cancel
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completed as if you had chosen the ok button (green check mark).
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ST22 details:-
Runtime Errors CONVT_NO_NUMBER
Exception CX_SY_CONVERSION_NO_NUMBER
Date and Time 09/16/2008 07:42:32
Short text
Unable to interpret " 1,410 " as a number.
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[whole number part].[fraction part]
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to
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If you have access to SAP Notes, carry out a search with the
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"CONVT_NO_NUMBER" "CX_SY_CONVERSION_NO_NUMBER"
"RSUVM001" or "RSUVM001"
"START-OF-SELECTION"
If you cannot solve the problem yourself and want to send an error
notification to SAP, include the following information:
1. The description of the current problem (short dump)
Information on where terminated
Termination occurred in the ABAP program "RSUVM001" - in "START-OF-
SELECTION".
The main program was "RSUVM001 ".
In the source code you have the termination point in line 96
of the (Include) program "RSUVM001".
85 * Analyze the user records.
86 CALL FUNCTION 'SAPGUI_PROGRESS_INDICATOR'
87 EXPORTING
88 text = 'Die Benutzerstammsätze werden analysiert.'(002).
89 * PERFORM analyze_user_records.
90
91 CALL FUNCTION 'SLIM_USER_MEASUREMENET'
92 CHANGING
93 SLIM_TUREP = LT_TUREP.
94 .
95 LOOP AT LT_TUREP INTO LS_TUREP .
>>>>> MOVE-CORRESPONDING LS_TUREP TO ITUREP.
97 APPEND ITUREP.
98 ENDLOOP.
99
100 * Submit Application measurements as batch jobs.
101 * Save additional data about this analysis in the DB.
102 * we need meas-no ,v-date at the batch
any ideas?

Hi Srikanth,
The below Notes helps you to solve the issue.
Please review the below Notes.
Note 1117010 - Runtime error CONVT_NO_NUMBER in RSUVM001
Note 1115924 - USMM composite SAP Note: Problems after importimg new SPs
Thanks & Regards,
Pradeep Srigiri

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Here are the results doing a real world file transfer from a macbook pro to a MacMini external FW800 drive:
Set-up
Peak speed MB/s
1) Macbook pro --> 1000Base-T --> Switch --> 1000Base-T --> MacMini (Time capsule connected to switch as router)
72.1
2) Macbook pro --> 1000Base-T --> Time Capsule --> 1000Base-T --> MacMini
56.2
3) Macbook pro --> 802.11n 5GHz --> Time Capsule --> 1000Base-T --> MacMini
19.7
4) Macbook pro --> 802.11n 2.4GHz --> Time Capsule --> 1000Base-T --> MacMini
14.8
5) Macbook pro --> 802.11n 5GHz --> Airport Express --> 100Base-T --> Time Capsule --> 1000Base-T --> MacMini
11.7
6) Macbook pro --> 100Base-T --> Time Capsule --> 1000Base-T --> MacMini
11.7
7) Macbook pro --> 802.11n 5GHz --> Airport Express --> 100Base-T --> MacMini
11.7
8) Macbook pro --> 802.11n 2.4GHz --> Airport Express --> 100Base-T --> Time Capsule --> 1000Base-T --> MacMini
10.6
9) Macbook pro --> 802.11n 2.4GHz --> Airport Express --> 100Base-T --> MacMini
7.9
10) Macbook pro --> 802.11n 5GHz --> Airport Express --> 802.11n 5GHz --> Time Capsule --> 1000Base-T --> MacMini
6.6
Findings:
- Using a Netgear Gigabit ethernet switch and everythig wired off that resuts in the fastest connection
- The Time Capsule has the fastest wifi (both 2.4GHz and 5Ghz) at 19.7MB/s and 14.8MB/s
- Maximum throughput on the Airport Express is 11.7MB/s, throttled by the slow 100Base-T connection
- Extending the wireless network using an airport express results in the slowest connection of all, even using 5GHz (6.6MB/s)
I was suprised at how poor the Airport Express wi-fi performance was compared to the time capsule, even with the 100Base-T bottleneck.
I don't understand why 8) is faster than 9) - perhaps with the airport express in bridge mode there is less overhead than when it is working as a router too.
Tests were done with devices all close. Obviously distance and interference would drop the wi-fi speeds. With my internet running at a maxiumum of about 2.6MB/s I would not notice any difference in day to day internet usage.

The following illustrates the problem:
Depending on the Extreme's firmware version, you may find an option to configure the Extreme to not "allow this network to be extended". That will limit the Express's available connection options to the Time Capsule.
Try that. If you are unable to find that checkbox in AirPort Utility then it's not an option. Apple removed it in a recent firmware update (it's always on by default). You might find it by reverting to an earlier firmware release, but I don't necessarily recommend that.

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