PCI-6251 Inter chennal effect is modifying signal.

Hi all,
Do anyone knows why we have inter chennal influence fo signal in PCI cards.
I am using PCI-6251 with BNC-2111, now if i connect cable in chennal 2 and read both the chennals then i am having signal in chennal 2 as well as in chennal one but not of same amplitude. the same thing i found with many other chennals.. I recently bought this setup (in January 2007). and i am new at labview. I am using this BNC connector with NRSE, and if i switch to RSE still no change in signal.
Can anyone help me in this regards..
Thank you very much in advance ..

Hello,
One of the most common issues with Cross-Talk is a high source impedance. So check your system if the signal you are connecting has a high (approx. above 10Kohm) input impedance. This can cause settling time issues in your ADC. Some more issues and possible solutions can be found in the following KB:
http://digital.ni.com/public.nsf/allkb/73CB0FB296814E2286256FFD00028DDF?OpenDocument
I hope this helps,
Regards,
RikP - National Instruments Applications Engineering
Rik Prins, CLD
Applications Engineering Specialist Northern Europe, National Instruments
Please tip your answer providers with kudos.
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Aquiring a signal using a PCI 6251

Hello,
I am trying to write a program that aquires a signal from a device connected to a PCI 6251. The device attached to the PCI is an esophageal lead and it is suppose to read a sine wave being sent through the body. Then I want to filter the signal and send it to a buffer. I do not have a good programming background, and I do not know if I can use LabView Signal Express or a function with in LabView 8.2 to aquire the signal. Any suggestions as to what I should do? Thank you.

Hi yed1920,
There are a few ways to acquire the sine wave. You can use a single DAQmx Acquire Step in LabVIEW SignalExpress and this will allow you to configure the acquistion and view the incoming data. You can check out some examples using DAQmx in LabVIEW SignalExpress which are found at C:\Program Files\National Instruments\SignalExpress\Examples\DAQmx on a Windows system. The LabVIEW SignalExpress Help and the LabVIEW SignalExpress Getting Started Guide which are installed with the program may also give you some direction.
If you choose to use LabVIEW, there are examples which can help you get started. The Example Finder can be accessed through the Help menu. The DAQmx examples can be found browsing by task under Hardware Input and Output » DAQmx. You can check out the NI-DAQmx Help file or the articles found on this page to learn more about certain functions in detail.
Regards,
Kent
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Data acquisition and frequency generation togather with PCI-6251 and LV8.2

Hi friends,
I am a new user of Labview. I am using LB8.2 with PCI-6251 .
I have to generate frequency and then measure the data and then for next frequency and so on.
i know that for this i have to use looping and that is not a problem. The real problem for measurement is to identify whether the frequency is been generated. if yes then measurements starts otherwise it should wait until it started. then after finishing the measurements send a signal to generator for changing the frequency and amplitude.
Now these two things {generation and measurement} togather are not working correctly for me. so i make 2 diff file, one for generation and other for measurements <by modifying the examples>. I can run both file togather and it works. But it need lots off effort and time. I have to measure from 10Hz to 1000Hz in 2Hz frequency step and i cannt leave in between .
can anyone help me how to syncronize these two togather .
Trying to attatch. both the files here ..
main_v1.1.vi --> for Measuring
Oscilloscope.vi --> for waveform generation
Attachments:
main_v1.1.vi ‏150 KB
Oscilloscope.vi ‏37 KB

Hay thnx dude..
I found the example and now it works
once again thanks a lot

Closed loop control of DC motor drive using PCI 6251

Hi
i am using NI PCI 6251 for closed loop control of dc drive.(shunt motor,220v, 0.5HP, 2.5A rated, 1500RPM)
the dc motor is fed from a bidirectional dc-dc converter. this converter works in boost mode(forword motoring) and buck mode(braking mode/battery charging)
the converter is built using mitsubishi IGBT module. at low voltage side of the converter a battery bank of 48V is connected and high voltage side the motor is connected.
An IR sensor is developed to measure the speed of the motor and a hall current sensor is used to sense the converter current.
in the control part i have an inner current control loop(PWM controller) and a outer speed control loop.both controllers are PI controller. To measure the speed i have used counter of the DAQ assistant, then frequency. then this frequency is converted to RPM using labview.after giving the speed and current signals to the controllers , then i started tunning the PI gain, but at the starting the duty cycles was 100%, so the IGBT got damaged immediately. now how to tune the controllers during the closed loop operation. the switching frequency of the converter is 20KHz.
can any body suggest me how to run the dc drive in closed loop ?
thanking you.

Hi Premenanda
The freq data receiverd from the daq assistant has the units of Hz, or in terms of motor speed, rps (rotations per second). I can see that you are trying to convert that to rpm (rotation per minute). which can be done by dividing the rps speed by 60. Instead, you are multiplying it by 60 and also comparing with 2000. the resultant multiplied value is displayed in your program only if it is smaller than 2000.which is causing the problem here.( as seen in file 'original code.png)
I have attached a file named 'modified code.png' that shows how the conversion from rps to rpm is done. Please do the required changes in your code and let me know if it works.
Attachments:
modified code.png ‏18 KB
Original code.png ‏15 KB

How to generate a pulse of 5 V -ve polarity in synchronisation with a 10 v input using PCI 6251 DAQ board

HI
I want to generate a 5V -ve polarity pulse to trigger my IEEE 1394 camera using an PCI 6251 (scb68 pin E) device, furthermore I am reading a standard Vsync signal from a SVGA port which is 10 v.
Now I want to synchronise the image capture of an IEEE 1394 camera with the Vsync signal so that camera is triggered to capture at every 4th Vsync signal (which is 50HZ.). Presently I am able to read the Vsync signal and also generate the -5 v signal But the Daq board generates a continues -5v signal while I want a 1 ms pulse (for every 4th Vsync).
Also this 5 v signal is generated even if the vi is stopped running.
Can anybody guide me so this problem can be solved.
Thanks a lot in advance
Shri

You can use the Write function, that is you can use the 10 volt signal as a trigger for the task, and when you get this trigger, the task starts and generate (writes) a waveform you defined in an array ("data", in the example).
Something like this..
DAQmxCreateTask("",&taskHandle);
DAQmxCreateAOVoltageChan (taskHandle, clokSource, your_sampling_freq, -10.0, 10.0,
DAQmx_Val_Volts, "");
DAQmxCfgSampClkTiming (taskHandle, clockSource, SAMPLING_RATE,
DAQmx_Val_Rising, DAQmx_Val_FiniteSamps,
samp_to_read);
DAQmxCfgAnlgEdgeStartTrig (taskHandle, input_channel, DAQmx_Val_RisingSlope, 9.0);
DAQmxWriteAnalogF64 (taskHandle, 1000, 0, 10.0,
DAQmx_Val_GroupByChannel, data, //data contain a pulse
&samp_per_channel, 0);
DAQmxStartTask(taskHandle);
// and then you create a loop....
For example you can specify data to be like this:
data[0] = -5;
for(i=1;i<1000; i++){
data[i] = 0;
Tell me if you need more help.....
bye

How to trigger 5v -ve polarity from pci 6251 to sincronise the image capture

Hello!
I want to synchronise the image capture of an IEE 1394 firewire camera with an 50hz input signal (acquired from Vsync of VGA port ). I want to accomplish this using PCI 6251 (SCB 68 E series) device. The IEE 1394 camera can be triggered using a 5V –ve polarity signal but have no idea how it is achieved, some examples about the application would be helpful
shri

This example illustrates how an application might be constructed in order to trigger an analog acquisition as well as an external system concurrently with an E-Series board. The analog component has been made retriggerable by tying a counter pulse train to its sample clock. Due to the complexities of the DAQ STC, an analog output line is employed in order to generate a hardware-timed, regular, pulse used to trigger both the analog acquisition, and potentially an external system. This type of architecture could be used for "stimulous - response" testing.
Attachments:
Timing_with_AO.vi ‏123 KB

WLS-9219 and PCI-6251

Hi,
We have PCI-6251 card for voltage acquisition at 200 sample/sec at 14bit. Now I see NI has new product for wi-fi wireless measurement. I see WLS-9219 (4-channel, 100 S/s/ch, 24-bit, ±60 V, ±25 mA universal input) may meet my requirement. But I am now sure and want ask NI expert, Does WLS-9219 can transfer 200S/sec at 14 bit???
Thanks
Liming

Hey Liming,
The 9219 does not have a flexible resolution and the max sampling rate is 100 S/s/ch. You will not be able to achieve 200 S/s/ch with this device.
What is the voltage range of the signal you are measuring? If it is within ±10 V then you may be able to use the WLS-9215, which is 16-bit and has a sampling rate of 100 kS/s/ch.
Regards,
Chris Delvizis
National Instruments

PI controller with PCI 6251

Hi all,
I am using DAQ PCI6251. Can I use this card for creating PI controller ?
Basically, I think that we can analyze a PI controller into two phases, including the proportional and integral phases. I could do this easily with Labview library. But I am facing a difficulty how to build the saturation block for PI controller ?
Pls give me the solution.
Thanks so much for your helps and supports.
Best regards,
Duy

Dear Jochen,
Thank you very much for your reply.
I can describe what I am doing as follows:
I would like to control the induction motor drive system with vector control approach.
The equipments in my system include the induction motor drive system, inverter, PCI 6251 Labview card, block connector BNC2110. I am using Labview 7.1.
I will gather the stator currents and voltages from the induction motor under analog signals. Then I will make some calculations on Labview with available Labview library. After that I will output two analog signals. PCI 6251 has two analog signals. I will use two analog signals from PCI6251 Labview card as input signals for PWM generating board which I could bulid. This PWM generating board will create signals to trigger IGBTs of inverter. And the inverter will create signals to control the induction motor drive system.
In this drive system, we need to use two PI controller as the requirement of vector control approach.
I hope that my description is clear.
The expected sample rate is 10 kHz.
I am using XP Window OS.
I attach the diagram what I need to do as well.
Thanks so much for your great ideas.
Best regards,
Duy
Attachments:
Practical_diagram_Labview_NI.pdf ‏27 KB

PCI-6251 into LABVIEW DAQ Assist block interruptions and resets

Signals being received from PCI-6251 into a LABVIEW DAQ Assist block interrupts and resets every 10 seconds after 1 minute of data acquisition. Would this be a memory buffer problem or is it something related to the hardware? I am using a BNC-2110 hardware connector. Please view the attached image.
Attachments:
Interuption1a.GIF ‏4 KB

Hey Peter,
Ahh, I understand the graph now! Hmm, this is very strange behavior. Instead of using the DAQ Assistant, try to use the explicit DAQmx VIs (see picture). You have more explicit control over what is going on with the DAQmx VIs and keep as much as you can out of the loop.
Regards,
Erik
Attachments:
analoginput.JPG ‏23 KB

Problem in edge separation measurement by using NI PCI 6251 card

I am trying to measure time delay between two TTL pulses (rising edge of the first signal and falling edge of 2nd signal) generated by two Photo detectors (APD) . These pulses are random pulses. Pulse width is 20ns and height is 2.5 volt at 50 ohm termination. I am using NI PCI 6251 card (M series card) for this job. I have attached my program and DAQ assist settings using for this job to this mail. Problem is   6251 card couldn't detect the pulses from APD. Exactly error shown is
                                                         "Error 200474: specified operation did not complete because the specified timeout expired".
I have tried by increasing the waiting time but it didn't solve the problem. I have tested my program with 20ns pulse width TTL pulses which are generated by a function generator, in this case my program worked well and given expected result.[both the signals are from same function generator and they are synchronized so edge separation measurement gives width of the pulse ] The height (voltage) of the TTL pulse generated by the function generator is 4v at 50 ohm termination. Is this height difference creating the problem? What can be the reason ? Can anyone suggest a better way to do this job.
                                                                                 Thanks in advance
                                                                                                                                                                                                                      Regards
                                                                                                                                                                                                                       surya
Research student
Attachments:
daqassist.jpg ‏71 KB
edgeseparatio.jpg ‏26 KB

Hey JmBone,
It's possible that you are just suppose to send a 32-bit integer to control the 32 valves. The 'byte offset' is probably just there to allow grouping of 8 valves (8 bits as 1 byte). So instead of sending an 8-bit number with some offset, you just send a 32-bit number and only change the bits corresponding to the valves you want to change. It would be easiest to just have a 32-bit binary array in your code for changine the individual valves and then cast that to a U32 integer before sending it to the Set Attributes VI. Maybe I am misunderstanding the manual, but I don't think 'byte offset' is a parameter you are suppose to specify, and is just there to indicate how the valves can be bundled into a single 32-bit value.
Regards,
Ryan

NI pci 6251 position control

Hi
Im new to this forum and new to Labview and NI pci 6251 as well ;(
I'm using NI-PCI-6251 (DC Motor ) with Labview to control the position of a DC motor we developed the program that reads the encoder and display the position of the DC motor shaft
but the problem is that the counter 0 (cnt0) always increases whether the disc rotating clockwise or anticlockwise??!! and when the desired position is reached the controller does nothing to stop the motor ?
i don't know what is the problem or why its happening.

Hi,
I am also doing something similar.
The problem is the motor is the DC motor from Quanser. (DCMCT).
I know the encoder channel of the motor is ctr0 and when I test from "Measurement and Automation Explorer" (Labview>>Tools) I can only read the PFI8 channel.
The motor read 4096 pulses per revolution and no reading is available from PFI10. As per Quanser the motor should be about to do position control. I have seen lab tutorials for position control in internet.
I tested both the vi is mentioned above. The "Example" vi reads the motor position in terms of pulses. But when I rotate the motor in the other direction the count increment not decrement.
Also the quadratureencoderMseries vi did not read the angle position when I set the channel values.
I have attached the parameters that I set.
Can any one please check..
Thanks.
Attachments:
encoder issue.JPG ‏357 KB

Brushless DC motor control using NI PCI 6251

am doing my project Speed control of a sensored Brushless DC motor. am using NI pCI 6251 daq. now my motor is running.but i dont know how to calculate the speed. in BLDC motor, hall sensor is attached. can you send me the sample program for calculating the speed and to give as a feedbackk

Will you please sent me VI model of BLDC ?
my mail id: [email protected]

Running LabView 7.1 with PCI-6251 in Windows 7

I am very new to Labview, and would appreciate any assistance on this issue. I was tasked with solving it and while I have made some progress I have now hit a wall.
A computer with a PCI-6251 data capture card, some custom built (external) hardware and LabView 7.1 has been used for many years for a single, specific task, to do verification testing in a manufacturing environment. The system works well and no additional features or functionality is required.
The computer failed and a new one with a PCI card slot was purchased to replace it. Of course as a new PC it has Windows 7 and hardware drivers for XP don’t exist. I therefore need to run LabView 7.1 on Windows 7 with a NI-DAQ card.
I installed the NI-DAQmx 9.5.1 driver and then installed LabView 7.1 (as discussed here). The driver would not install if LabView was already installed since it gave the “unsupported on this version of windows error”. MAX recognized the card, which it couldn’t when trying to use the 7.5 NI-DAQ driver.
Now LabView opens but when I try to run the .vi used for testing it complains of 19 missing sub .vis which I cannot locate and I can’t find on the old computer to try to point LabView towards.
I think something weird is occurring with trying to use the 9.5.1 driver with LabView 7.1. Are there any suggestion or is there any advice on getting a PCI-6251 working with Labview 7.1 on a Windows 7 machine?
Solved!
Go to Solution.

After much greif and trying a half dozen various drivers with various settings and other ideas the following procedure based on Caraval's advice worked first time with no errors and seemingly no functional issues. The system so far appears to be running in Windows 7 just as it was on Windows XP.
1. Install LabView from original install CDs, by opening the folder and right-clicking 'setup.exe' and clicking 'run as administrator'. Selected 'do not install drivers' during the install procedure. Rebooted computer.
2. Installed NI-DAQmx 8.9 from the self-extracting .zip file available here. Shutdown computer.
3. Removed power, pressed power button to completely discharge power supply. Installed PCI-6251 card.
4. Booted computer, and logged in. Waited a long time, Windows eventually saw new hardware and installed drivers. Verified MAX could see card.
5. Opened LabView and everything worked.
Looks like we bought the system a few more years. Will probably have to upgrade everything next time around though. Many thanks to everyone who commented on this thread.

Using PCI-6251 with Labview 6.1

I recently purchased a PCI-6251 multifucntion DAQ board to get a higher sampling rate than my old PCI-MIO-16E-4 board. However I have existing software that I want to run on the new board. The board came with NI-DAQmx which will only work with Labview 7 or above. I am currently running NI-DAQ 6.9.3 and the Measurement and Automation program does not recognize the new PCI-6251 board. Is there anyway to get Labview 6.1/NI-DAQ 6.9.3 to recognize and configure the new board? Or will I be forced to upgrade my Labview?

The M-series boards (PCI-62xx are M-series) require NI-DAQmx driver. The NI-DAQmx driver requires a newer Labview. No way around it.
John Weeks
WaveMetrics, Inc.
Phone (503) 620-3001
Fax (503) 620-6754
www.wavemetrics.com

Pci-6251 soprta tiempo real

Buen día:
Quiero implementar un control de velocidad de un motor de cd en tiempo real, cuento con una tarjeta PCI-6251, el sensado de la velocidad es un encoger incremental.
Preguntas:
¿La tarjeta PCI-6251 soporta el tiempo real?
¿Existe algun ejemplo para estudiar su implementación?
Cuento con LabVIEW 8.0 y tengo instalado el modulo Real-Time.
Tengo algunos problemas con el tutorial Real-Time.
Gracias de antemano.

Estimado itlcarlos
Gracias por utilizar los foros de National Instruments.
En primera instancia quisiera entender a lo que te refieres con "Tiempo real", ya que tiempo real indica que estarías trabajando bajo un sistema operativo determinístico con el cual te asegurarías que existe confiabilidad total en el sistema, de ser así no podrías trabajar en Windows ya que no es determinístico. Si intentas ver la tarjeta como un dispositivo RT no va a ser esto posible en el proyecto de LabVIEW.
Ahora si te refieres con Tiempo Real a que la tarjeta trabaje de manera confiable y envíe la información en tiempo y forma al sistema operativo, te sugiero revises la hoja de especificaciones para que determines si la precisión y el reloj son suficientes para tu aplicación
Me gustaría me aclararas si esa era tu pregunta o me detalles un poco más que es lo que intentas hacer y con todo gusto te ayudaré.
También dime que problemas tuviste con el tutorial de Real Time para ver en que te podemos ayudar.
Que tengas un excelente día.
NI 625x Specifications
http://www.ni.com/pdf/manuals/371291h.pdf
Coamín Cruz
Ae México

PCI-6251 Inter chennal effect is modifying signal.

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