Tim_S

QUOTE (Stijn @ Apr 15 2008, 02:11 PM)

All the sensorsignals has been simulated but now we've got to simulate the crank shaft signal, this is a inductive sensor that stands next to a flywheel, on the flywheel there are 35 theeth and after the 35 theeth there is 1 thooth gone.

I'm half-surprised you're using a passive sensor as most cam/crank sensors I'm seeing are active and output a digitized signal.

Tim

QUOTE (superslug @ Mar 25 2008, 12:20 AM)

we are having problems printing using labviews native print with a new printer. It is a canon pixma mx850 and it blue screens whenever we try to print from labview on an xp machine. When we print from our vista computer it is fine. I was wondering if anyone else has come across this sort of thing?

I've not had this problem with printing and LabVIEW (pleanty of others, though), but the first thing that comes to mind is the print driver may be causing the problem. I would recommend performing a complete uninstall and clean on the driver and then then reinstalling the driver. You could also verify that the driver could be a problem by trying to print from various applications.

QUOTE (ASTDan @ Mar 17 2008, 04:37 PM)

Does anyone know if I can hook up 2 computers to monitor a single RS485 device?

You can hook PCs together on one RS485 network. Think of it as a networked version of RS232.

QUOTE (ASTDan @ Mar 17 2008, 04:37 PM)

Loading will depend on the rate that the device sends out data. Ground loops should not occur so long as you hook everything up per RS485 specification. Line loading won't occur unless you exceed the RS485 specification (seems like it's 32 devices on no more than 1000 feet, but I'd have to look it up).

The digital outputs on the NI cards are not going to be sufficient to drive anything like a motor. You will need a power amplification stage between the card and the motor. I assume this is a small motor, but it will still generate comutation noise. You'll want to keep this noise from the DAQ card so that 1) it doesn't damage the card, and 2) you don't want it to get to the other channels.

Unless the card is built specifically to handle the loads you're connecting, it is always good practice to provide an isolation layer between the card and the hardware. This has saved many a PC when something like arcing the 24-volt logic from the 480 VAC three-phase occurs (fortunately no one was hurt).

QUOTE (carlover @ Mar 12 2008, 12:17 PM)

- is there a way to simultaneously acquire from three USB cameras?

If NI is telling you that the driver can only acquire from one camera at a time, then the only way to acquire from more than one camera at a time would be to change drivers. This would include using multiple applications as the driver would be common the all of the applications.

From my understanding of LabVIEW and vision, I would say the issue wasn't the choice of LabVIEW/NI, but the choice of using a USB camera system and the limitations that supplies.

For the synchonization part, that depends on what you mean by synchonization.

Tim

QUOTE (dasrobie @ Mar 12 2008, 12:20 AM)

Friends any one of you have worked with this device--Agilent--16700.I have been told by Agilent guys that i need to use intuilink COM for controlling the device remotely from a host PC.Has any one of done remote controlling of the device through COM.Can you please send some example Vi for my reference.

Looking forward to get some valuable suggestion.

Are you refering to COM as in the serial port or COM as in a COM (ActiveX) control?

Tim

QUOTE (vt92 @ Mar 11 2008, 02:25 PM)

Hello all,

I'm looking for a DAQ device that meets the following requirements:

1.) USB interface

2.) At least one 12 or 16 bit D/A port

3.) At least one 12 or 16 bit A/D port

4.) At least 8 I/O channels

5.) On board pulse generation capability. (square wave, 1 Hz - 10kHz)

I have waded through NI, Measurement computing, etc and haven't found exactly what I want. Your recommendations would be appreciated.

You may want to use the NI webpage under the Products & Services "tab". There is the ability to filter through DAQ hardware based on such requirements.

QUOTE (Bob Edwards @ Mar 11 2008, 12:55 PM)

I'd appreciate a few suggestions on achieving the 'message bus' that doesn't involve the creation of a multitude of individual links. Anyone solved this one with datasocket? I'm toying with time slewing messages based on registry entry, or arbitration on the part of the registrar, or some kind of handshaking suited to datasocket. Can't put my finger on a 'KISS' method at the moment. Doesn't help that datasocket server behaviour isn't that well documented.

All suggestions welcome,

Cheers, Bob Edwards (EMC test engineer)

Datasocket is a "catch-all" for communicating, so it has a fair number of quirks (besides the limited documentation). Datasocket is good for small numbers of variables (I believe the number I've heard is 200 as the upper end); large numbers of variables cause performance (mainly delay) issues. This is something to keep in mind with your design.

You may want to consider something such as TCP, though if you have multiple listeners it seems that UDP would be more appropriate (UDP is not as reception robust which may not be an issue on one machine).

As a thought, it sounds like you're creating a plugin-like archetecture. You may want to consider alternative design structures, all of which depends on your design constraints. You may even want to consider something off-the-shelf such as TestStand if you need to integrate in C code as well as LabVIEW code.

Tim

QUOTE(Aaron L @ Mar 5 2008, 07:21 PM)

All I want to do is wait until I receive a CR/LF combo from a serial port, 9600/8/N/1, then execute the rest of my code. I looked at the example codes built into LV 8.5 to no avail. They have reads, simple and complex, but all of them time out rather than stopping on my CR/LF character combo. Really, all I need is the LF character. It can't be this difficult, right?

Years ago I had to do this and wound up reading the serial port then buffering the string. I've not looked to see if there are newer tools that can do this, but I'm suspicious that's what you're going to be doing.

QUOTE(JDave @ Mar 5 2008, 03:41 PM)

How can I determine if LabVIEW is the active (frontmost) application? I know that you can set a VI to be floating and automatically hide when LabVIEW is not active. But is there any way to access that information via an event or property node? If I had a floating VI, I could check if it was hidden or not -- but to make it interesting let us assume that is not an option.

David

In the user32.dll there is a SetWindowPos function that can be used to make the window the frontmost. I didn't see a get or query counterpart in a brief search, but that would be the place to look.

Tim

QUOTE(kanmo @ Mar 4 2008, 07:30 PM)

When i was building .exe instead of .dll, i could achieve this simply by clicking STOP button.

However, with dll I can't activate the application interface window.

Is it possible for dll to have interactive graphic interfaces?

Yes. This would require basically the same VI properties as if you had a user interface in a subVI.

QUOTE(CamilloN @ Feb 28 2008, 02:41 AM)

What if i make a fast fourier transformation than overwrite the unwished

frequencies with zeros and make than a inverse FFT? This could also be

possible, or are there any problems.

Now a question to all mathematician out there ;-)

I know that the FFT mirrors the frequencies. What happens if i also overwrite

the mirror-frequencies? Are they necessary for the inverse transformation?

I've used an inverse-FFT filter before, though it was using the one-sided versions. It worked rather well so long as the frequency content of the noise was "sufficiently far away" from any frequency content of the signal. You will get distortion of the original signal if the signal and noise intermix. With the signals I had, there was a fine line between not eliminating noise and eliminating signal, so you may have to play around with the frequency threshold more than with other methods.

QUOTE(fuzzycontrolfreak @ Feb 25 2008, 08:35 AM)

Hello everyone,

I am acquiring a digital signal from a rotating shaft encoder. The square wave comes at a rate of 36,000 pps, at almost constant intervals. What sampling rules does this application follow. Shall I go after the Niquist Criterion, or a 36kS/s is enough to catch all the signals.

Thankyou very much for your help.

If you know you're getting a 36 kHz signal and you want shape data, then you should be sampling at ten-times the expected maximum frequency (twice for frequency). The sugestion of the encoder is good if you want to be synchronous to the shaft (data collected in constant degrees apart rather than time). What you intend to do with the data after you've collected determines which method would be best.

Tim

QUOTE(CamilloN @ Feb 25 2008, 04:07 AM)

How can i plane (is that the correct word for my intention???)

the Signal WITHOUT moving the Signal to the left or to the right.

Or is there another Method to calculate the dy/dx

I believe the word you're looking for is "filter". Time/phase shifting can be a problem with filters. There are some that are designed to have no phase shifting but those tend to affect amplitude instead. Depending on the filter settings and your data, neither phase nor amplitude may be affected in the areas you want to keep.

You may want to try a "running average" filter. This involves taking multiple sequential points and averaging them; the effect tends to take out little spikes. The number of points you use can impact the portion of your data that you want to keep.

QUOTE(dblk22vball @ Feb 6 2008, 02:12 PM)

Has anyone done anything like this before?? Thanks.

I've heard of spray patterns being detected before, but it was with a custom-built capacitive-based sensor array in an R&D lab environment.

What you seem to be describing is a more 3D version of web analysis (I think that's the proper term), which is detecting features of anything streaming by at high rates of speed. Such applications include detecting applied glue, thickness of paper, and bubbles in molten glass (fiberglass production). For something at lower rates of speed, there is an NI demo of detecting how full a soda bottle is on an assembly line.

QUOTE(Phil Duncan @ Feb 5 2008, 01:14 AM)

Hi All,

First off, if there is a more appropriate forum for this topic, please let me know and I will bother them instead . However, since I will be acquiring and analysing the data from the sensors using LV, I am hoping someone here has already done this.

I need to measure the angular travel (max travel angle) and angular travel rate of a UUT using distance sensors (ultrasonic/IR etc). The UUT is a 76mm diameter plate that may be flat mirror glass, (chrome or glass first surface), curved mirror glass, stainless steel or black moulded plastic (with or without textured finish) oh and the UUT can be all of the above coated in a layer of frost, dust, salt or mud. I also need to measure current draw but that is easy.

The expected angle of travel is +/- 20 degrees from central position at 0-6 deg/sec.

Sample rate of 1kHz and linear accuracy of +/- 0.012mm, angular accuracy of +/- 0.01 degrees is also required.

It is anticipated I will use 3 or 4 sensors to calculate angles and angular rates.

Does anyone know an appropriate sensor that will achieve this?

I have found a few sensor sites but I cannot find the tech data (accuracy, sample rate etc).

Any and all help is very greatly appreciated.

Cheers & Beers

:thumbup: :beer:

What is rotating the surface? It seems an encoder would work for your application.

QUOTE(Natu @ Feb 4 2008, 03:57 PM)

Since I am making One Operator Training Simulator (OTS) for Tharmal Power Plant with the help of LabView. In which there will be number of Systems. And each System will have number of equipment like Pump, Valves, Tanks etc. So for each system I will make One SubVI where all the operation seqence and control logic will be implemented and here I will give some time delay to fulfill the requrement. And each subVI which is representing a corrosponding System, I will call in MainVI to reduce the over all VI size. Now as you are asking for MainVI it is very difficalt to send. Thats way I had simlified my question. And what I am understanding as Mr. JFM is telling it is not possible to set some SubVI property to satisfy my requirement. So I am manipulating like shown in attachment.

JFM has the right of it... the VI is operating based on your longest delay.

Tim

QUOTE(Natu @ Feb 4 2008, 06:35 AM)

Thanks for reply Mr. Martin

I am very sorry I am late because my PC is hanging frequenty because that only by mistake I sent my question in two categories.

I am attaching three Flash Generator with differenet timing. When I am calling these, in main VI it is not flashing LED with the frequency what I have discided while making. Whereas individually it is working.

It would help if you posted your main VI as well.

QUOTE(Lars915 @ Jan 30 2008, 04:57 PM)

We don't use DSC, but we use various combinations of LabVIEW as a front end to control TestStand while it's calling LabVIEW in a driver layer, both in production and in new product development. The latest version of TestStand is far superior to versions 1 and 2, and is quite a step up from 3.X.

You may want to take another look at TS4.x. They've done a lot of work on appearance, and the user interface layer (used by LabVIEW) is vastly different than all other releases.

Thanks.

The activeX interface from LabVIEW to TS4.x looks like a significant learning curve task; I'm not sure what to make of it yet. I'm still trying to wade through the manuals. DSC is rather dissapointing in that it doesn't have very good example code nor can I find any manuals installed with DSC.

Tim

QUOTE(Francois Methot @ Jan 30 2008, 05:46 PM)

Hi,

I read and learn the LabVIEW for Everyone book. I have lots of GPIB RF equipment in my lab. I am looking now for books that will help me to start programming some basic control with GPIB. I was able to find most of the drivers needed. Is there some references programs?

Thank you

If you look in the Example Finder and look through NI's website (they have an instrument driver section), you should find what you're looking for.

An option has been proposed to me to use LabVIEW as a front end for TestStand and the Data Supervisory and Control Module in a test executive application where there is data acquisition, OPC communication, reporting, calibration, error logging, parallel execution and test/limits configuration. (The reason for LabVIEW front end is DSC and TestStand won't meet customer requirements alone.) The last time I saw TestStand was version 1 (there was lots of colorful metaphors used at the time) and I've not used the DSC module.

What has people's experiences been with any combination of these?

Thanks,

Tim

QUOTE(jennifer @ Jan 28 2008, 11:58 AM)

Hi,

this new vi contains a few lines of the csv file. It works better now with strings. Thanks for your hint. I want to show the first two strings in a row in a diagram. How can this be realized?

Thanks for your support.

You could open the file and use "Read from Text File" to read n number of lines. You'll have to right-click on the primative function and check Read Lines to do this. The Spreadsheet String to Array primative would also be useful.

Tim

QUOTE(bayram_mercan @ Jan 25 2008, 07:31 AM)

i mean if i take signal for 5 seconds, i want to get 500 values. but i get last 100 sample values.

for the time, i wnt to get the exact time for each sample value.

Converting the dynamic data type to a waveform will provide you t0 and dt. From there you can get the array you're looking for.

QUOTE(jennifer @ Jan 25 2008, 06:04 AM)

Hi,

in this attached vi, i want to read data from a csv file. The problem is, that i can not picture the right format.

In the first coloum i only get the the 19, in the second 14 and so on of 19.02.2004 13:00:00,14.5500,2.6120,423.5600,1.2561,1.9590

Couldn't upload the csv file.

Would be great, if anybody could help.

Thanks, Jennifer

It would help if you'd attached a sample of your csv file.

Based on your description, processing the file as a double won't give you the proper first value as it's a timestamp and not a double. You'd have to process everything as a string array to preserve the timestamp. After that you'll have to process the strings.

Depending on what you're doing, there may be better ways of processing the csv file.

QUOTE(Neville D @ Jan 23 2008, 02:01 PM)

I have heard that the reason the ini VI's are slow is because the native LV VI's themselves are a bit ancient and clumsy. You can try these http://www.mooregoodideas.com/goodLabViewStuff.htm' target="_blank">VI's from David Moore that are supposed to be much faster since they replace the native VI's.

I haven't used them before.

Neville.

The LabVIEW VIs for INI files are definitely slow. It's not bad on small files, but very noticable with large files. My initial workaround for reading in the INI file was to read in the entire file as a string and then process the lines. I don't remember the time difference at the moment, but it seems like it was an order of magnitude change.

I've not used the David Moore VIs. Can anyone relate how they compare?

Tim