Lego and DAQ

Hello there, I am using a sensor attached to the SCB 68 connecting block of my PCIe 6321 NI X DAQ device.
Is it at all possible to connect lego NXT to the same connecting block so as to use the sensor and lego NXT together in Labview?

Hi Jolanta,
I have created a quick VI that shows that you can read data from a PCI DAQ Card and read data from an NXT sensor within the same VI. Therefore it should be possible to read your sensor data and control your NXT motors.
Please let me know how you get on.
Regards,
Ben B.
Applications Engineer
National Instruments UK & Ireland
"I've looked into the reset button, the science is impossible!"
Attachments:
NXT with DAQ.vi ‏58 KB

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Hello
everybody,
I am using the measuring board (NI PCI 6221) and DAQ
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I do not know the type of sensor you are using. But pressure transducers may have a very low output voltage(in the mVolt range). They also need an excitation voltage. Here is an introduction. http://focus.ti.com.cn/cn/lit/an/sloa034/sloa034.pdfThen working with pressure sensors I always use 3 stages in the circuit.
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Synchronizing serial and daq data

Hi,
I'm attempting to acquire simultaneous data from a serial port and a NI USB-6211 board.
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Solved!
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Would it be possible to post your code?
You could sync your loops with a "wait until next ms tick with a value of 1000. This would cause both loops to execute once ever second at at the same time.
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Hello..
i have a project that i need to design a Spectrum analyzer with simulation mode and DAQ option. ( so you can generate input signal from LabView and DAQ.
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http://digital.ni.com/worldwide/singapore.nsf/web/all/42B390E4624228D486257249001A5349
this kind of Spectrum anlyzer looks great
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Hi Eldad,
Thanks for posting and welcome to the NI forums!
The
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NI-DAQmx: Benchtop Spectrum Analyzer
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are also numerous examples that are installed with the DAQmx Driver to
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Help >> Find Examples... >> Hardware Input and Output >> DAQmx
There
may not be a ready-made example that will do everything that you
require, but the above should give you a good starting point for
implementing the necessary features yourself. If you run into any
specific issues while trying to program, please don't hesitate to post
to the forum and we'll be more than happy to help out.
-John
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i want to measure the resistance of the SMA wire without any current in put by LAB view and DAQ-9172 any body help me

You could measure the time constant of a resistor/capacitor series circuit. Basic electrical engineering: http://en.wikipedia.org/wiki/RC_time_constant

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Hi eveybody
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Check with the vendor to see what they might have. Otherwise, you will need specs on the communication interface and then write your own driver.
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Synchronisation of frame grabber and DAQ board

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Hi, Peter,
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Best regards,
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Applications Engineer
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FPGA and DAQ card synchronization

Hi, we are controlling and acquiring data from multiple hardware devices (including translational stages and photodetectors). Until last week, we used to peform all control and acquisition using a PCIe 7852R FPGA board. However, we decided to switch the acquisition part to a PCIe 6363 DAQ card to improve the voltage resolution. During testing, I found that the internal clocks in the FPGA and the DAQ cards are slightly mismatched (not just a phase delay, but a difference in time-period).
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Regards,
Varun
Solved!
Go to Solution.

Hi GerdW,
Thank you for your reply.
I understand both solutions you have suggested. I had conceptually thought about the first one (to control the sampling rate). However, I still haven't figured out how to accurately generate a 200kHz square wave - I think I can figure that one out this morning.
However, I am unsure how to implement the second option. I presume the default internal clock inside the DAQ is running at 100MHz or so. Therefore, inorder to obtain the same performance while using an external clock, I would have to generate at least a 80MHz TTL clock-out from the FPGA. Could you please tell me how I can do that? I couldn't find any clock-out capabilities on my FPGA. Or would I have to generate a clock of my own using Single-Cycle-Timed-Loops?
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Thank you very much.
Regards,
Varun

Simultaneous Video and DAQ Start

Pardon my ignorance in the signals world, but I'm having a hard time trying to simultaneously start a video camera and DAQ hardware. Hopefully someone can provide some insight.
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Nathan - Certified LabVIEW Developer

Nathan,
What kind of camera bus are you using; USB, FireWire or GigE? Are you able to acquire images with your camera in Measurement & Automation Explorer (MAX)? Here is a link to a community example that Grabs and Saves to AVI using IMAQdx. If the camera has digital i/o lines to accept the TTL signal pulse you can run the example I've linked to and configure it for a triggered acquisition in MAX. The camera's user manual should specify which pins are trigger lines or whether a specific i/o cable are terminal block is necessary. If the camera supports triggered acquisition you can go into MAX select the camera under Devices and Interfaces the select it's Camera Attributes Tab. There should be an attibute called "trigger mode" and its default setting is off so you would need to turn it on. If there are multiple trigger lines, you would need to specify the "trigger source" under its allotted attribute. Some cameras can only trigger the start of an acquisition while others can also trigger each frame acquisition. You can specify whichever you'd like under the "Trigger Selector" attribute.
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A problem with delays in timed loops and DAQ

I am programming a simulation for nuclear rewetting for a visitor centre at my company in Switzerland. It involves heating a "fuel rod" and then filling the chamber with water. The pump automatically starts once the rod core reaches 750C. After this, a requirement stipulates that flow rate be checked to ensure the pump is operating at the necessary conditions. If it isn't, the heater must be shutdown to avoid, well... meltdown. However, we must allow 10 seconds for the pump to respond, while still allowing a DAQ rate of 10-100Hz.
The challenge is that I can't add a delay in my main loop else delay all acquisition, but I can't figure out how to trigger a peripheral loop (with DAQ for the single channel of checking flow) from the main loop, and when the peripheral loop determines if flow has initalised, respond back to the main loop with the okay.
I think much of my confusion is in the interaction of the loops and the default feedback nodes that labview is putting in willy nilly. Would the only solution be to have two 'main' loops that don't communicate with eachother but rather do the same thing while operating on different timing? Tell me if you want me to post the file (although its on an unnetworked computer and I didn't think it would be too useful).
Thanks+ Curran
Solved!
Go to Solution.

Here it is! It is not in any form of completion unfortunately.
So reading in the temp with NI9213 and watercolumn height with NI9215, we determine to turn on the pump with NI9472. NI9421 determines whether the pump is on (there is flow) and I must respond accordingly.
I have 3 scenarios similar to this one as well, so having redundant loops with different timing like I mentioned would be way to heavy. I think I may have though up of a solution? At the time the pump is initiated, we record the iteration and wait for a number of iterations that correspond to 10s to pass before fulfilling the pump shutoff requirement?
Attachments:
rewettin1.vi ‏15 KB

Inconsistent frame and DAQ rate

Hi,
I have written, LabVIEW 7.0, a code (attached) to read from a DAQ card, 3 Visa's and 2 Firewire cameras. Before I included the cameras, everything worked fine. With the cameras, the performance decreases with time (the longer the acquisition time is, the lesser the frame rate). My questions:
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2. Is my approach in getting capturing the images an "OK" way, or is there a better way in doing it? This is my first time 'playing' around with IMAQ 1394.
3. I have a hunch that if I save every images once it is in the buffer, instead of capture everything first and save later, would increase the performance. Can this be true?
4. Last, is there a quick and ea
sy way to produce an AVI file from the recorded images? I realize that the elapsed time between the images is different and this cause an additional headache in producing the AVI file.
By the way, the desktop I am using is a P4 2.4 GHz, with 1024 MB of RAM (if I'm not mistaken). I hope what I said make sense here and I highly appreciate all the help I could get Thanks!
Shazlan
Attachments:
NIPost.llb ‏539 KB

Shazlan,
The first thing you can do to optimize your code would be to use only one IMAQ create. In your code the IMAQ create is inside the loop so you will be using more and more memory as the program runs. I have attach an example with 1394 that I wrote. It has only one IMAQ create. The example also has a implemented a save to AVI for saving the images. I hope this help
A. Talley
Applications Engineering
National Instruments
Attachments:
Grab1394_and_Save_to_AVI.vi ‏102 KB

Acquire encoder position with Motion and DAQ

Hi,
I am trying to acquire an encoder position with Motion. It seems impossible to set the frequency of the acquisition with Motion and I must poll for the position in a do-while loop.
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PS: please don't answer with measure angular position.vi or explain me in what this Vi can help me

Hi Christophe,
I'm not sure I understood well what you need. You have the angular position and you need to know the timing, am I right? Can you use an other counter on your card to get the period (or the frequency) of your signal? From that, I think you should be able to calculate the velocity.
I hope this helps,
Charlotte F. | CLAD
National Instruments France
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How to synchronize NI-Scope and DAQ

I use a PXI-1042 System with a PXI-5124 Ni-Scope Card and a PXI-6120
with traditional DAQ controlled by a PC running WinXP and LabView 7.0
The intention of this setup is to make synchronized acquisition with
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assume the NI-Scope runs at 100MS/s and the DAQ (6120) with 100kS/s. The Trigger is generated by
analog triggering of the 6120. I'm looking for a solution to garanty
that for a STOP trigger with post-trigger scans the last sample of the
6120 coincides in time with the last sample of the NI-Scope 5124 card.
Or to put it in more general terms a way to identify which of the 1000
Samples the 5124 Card takes in the sample interval of the 6120
coincides with the respective sample of the 6120 ? The point is to have
a time resolution (for phase difference measurements) better than that
given by the samplerate of the PXI-6120.

Here you can find an example that shows how to synchronize a DAQ-Device with a Scope-card:
http://sine.ni.com/apps/we/niepd_web_display.display_epd4?p_guid=B45EACE3E2C556A4E034080020E74861&p_node=175382&p_source=External
Hope this helps.

Control Design and Simulation and DAQ

I'm learning Control Design and Simulations. I have some questions about it.
1. For System Identification use, we can find the transfer function/model of the system by feeding data measurement from the system. But, how long data do we need to be sufficent for Identification System to estimate the model? Until the get saturated value (steady state)? or any other intervals? What if the system is unstable? How will Identification System Toolkit estimate that case?
2. For connecting to hardware, we just connect the clock in the simulation loop to the hardware? And the simulation loop will simulate the blocks inside once it got the trigger/data from the DAQ? what about the step time and solver? Do they follow the timing from hardware? or they will run on their own supplied values/clock?if we use USB DAQ, we can't have any clock from it (as far as I know it's because USB connection is not that stable for clocking since it might be any jitters or delays.) So, how do we configure the timing parameter for USB DAQ?
3. There is possibility to convert model in transfer function to state space, how do we know the states inside that conversion?
Any helps would be great...
Thanks in advance...

Dear Chin ho,
After going through your questions I found some documentation which will be useful for you. But I you still have more questions, you can reply me any time.
1- About the data and amount of it I couldn't find any info but maybe you can use the new functions in LV version 2009 and find your answer.
Estimating States of Nonlinear Stochastic State-Space Models with Extended Kalman Filters
In previous versions of the LabVIEW Control Design and Simulation Module, you can use the Discrete Kalman Filter function and the Continuous Kalman Filter function to estimate the states of a linear discrete or linear continuous stochastic state-space model, respectively. In the LabVIEW 2009 Control Design and Simulation Module, you can use the Continuous Extended Kalman Filter function and the Discrete Extended Kalman Filter function to estimate the states of a nonlinear continuous or a nonlinear discrete stochastic state-space model, respectively.
The Continuous Extended Kalman Filter function and the Discrete Extended Kalman Filter function estimate model states of a partially observable plant based on noisy measurements. First, use the SIM Discrete Nonlinear Plant Model template VI or the SIM Continuous Nonlinear Plant Model template VI, located in the labview\templates\Control and Simulation directory, to define the system model. Then use the the Discrete Nonlinear Noisy Plant function or the Continuous Nonlinear Noisy Plant function to simulate the discrete or continuous nonlinear model, respectively, with the addition of noise. Finally, use the Continuous Extended Kalman Filter function or the Discrete Extended Kalman Filter function to estimate the states of your model.
The Continuous Extended Kalman Filter function and the Discrete Extended Kalman Filter function linearize the nonlinear system either by calculating a Jacobian matrix internally or by using an external Jacobian matrix that you define. Use the SIM Continuous Jacobians template VI or the SIM Discrete Jacobians template VI, located in the labview\templates\Control and Simulation directory, to define an external Jacobian matrix.
Refer to the LabVIEW Control Design User Manual, accessible by navigating to the labview\manuals directory and opening CD_User_Manual.pdf, for more information about estimating the states of nonlinear stochastic state-space models with extended Kalman filters.
2- I think that I found a pdf document about this part of your question which will be helpful. If you would like to give your email address, I can send it to you.
3- About this part you can check the help function in LabVIEW when you open the "CD Convert Transfer function To State-space" function in your front panel.
I pasted some info about the mathematic part below.
The LabVIEW Control Design and Simulation Module provides tools to study the dynamics of systems described by linear time-invariant (LTI) continuous and discrete models. You can create deterministic state-space, transfer function, and zero-pole-gain models. You also can create stochastic state-space models and the second-order statistics noise models. You can use these forms to describe both single-input single-output (SISO) and multiple-input multiple-output (MIMO) systems.
Continuous transfer function and zero-pole-gain models use the s variable to define time, whereas discrete transfer function and zero-pole-gain models use the z variable to define time. Continuous state-space models use the t variable to define time, whereas discrete state-space models use the k variable to define time.
Deterministic State-Space Model
Continuous
x(t) = Ax("t) + Bu(t)
y(t) = Cx(t) + Du(t)
Discrete
x(k + 1) = Ax(k) + Bu(k)
y(k) = Cx(k) + Du(k)
Stochastic State-Space Model
Continuous
x(t) = Ax(t) + Bu(t) + Gw(t)
y(t) = Cx(t) + Du(t) + Hw(t) + v(t)
Discrete
x(k + 1) = Ax(k) + Bu(k) + Gw(k)
y(k) = Cx(k) + Du(k) + Hw(k) + v(k)
Second-Order Statistics Noise Model
Q = E{w . wT} – E{w} . ET{w}
R = E{v . vT} – E{v} . ET{v}
N = E{w . vT} – E{w} . ET{v}
where
t is continuous time.
k is the model sampling time multiplied by the discrete time step, where the discrete time step equals 0, 1, 2, …
x is the model state vector.
u is the model input vector.
y is the model output vector.
w is the process noise vector.
v is the measurement noise vector.
A is an n × n state matrix of the given model.
B is an n × m input matrix of the given model.
C is an r × n output matrix of the given model.
D is an r × m direct transmission matrix of the given model.
n is the number of model states.
m is the number of model inputs.
r is the number of model outputs.
G is a matrix relating w to the model states.
H is a matrix relating w to the model outputs.
Q is the auto-covariance matrix of w.
R is the auto-covariance matrix of v.
N is the cross-covariance matrix between w and v.
E{} denotes the expected value or the mean of the enclosed term(s).

Magma-box and DAQ PCI 6034E card

I had installed a magma-box (64-bit 2 Slot Series) on my laptop. And I installed NI-DAQ 7.1. Than I had plug the PCI-6034E card in the magma-box. My laptop identify the PCI-6034E daq card in the Device Manager; but with a yellow exclamation point and give the Error code 10 (Cannot start the device). The same used with the PCI-6377 card.
I have tried with the cards in the differend slots.

Hey Wim,
I am not sure what a magma-box is. I have searched all over google and I haven't been able to find one. This brings up my next question of how you are installing a PCI-6034E and PCI-6377 on the laptop. National Instruments driver does not support this and I am pretty sure the DMA on the devices wouldn't work as well. The main difference between the PCMCIA devices National Instruments sell and the PCI devices is the DMA channels. If you need to use a laptop I would recommend purchasing the DAQCards or DAQPads that can connect to USB, Firewire, or PCMCIA slots. These devices are supported on laptops. The PCI devices are designed to work on desktop computers with standard PCI busses that allow for DMA channels and ISA based interrupts.
I hope
this helps out.
Joshua P.
Application Engineering
National Instruments

Lego and DAQ

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