Current loop measurement and DAQ board

Hi.
I want to acquire some values coming from sensors outputting a 4-20 mA signal.
I designed a solution with SCXI-1125 and E series card.
In other side, somebody -from NI- gave me a price offer with just E-Series DAQ card and a connecting board with resistors (and thus measuring Voltage). I can understand this solution (when the range are compatible).
So, can you explain me what are the benefits if I choose the most expensive solution (SCXI + E-series)compare to the cheapest one (E-series + resistor)
Thanks a lot.
SB.

Basically, the SCXI solution would provide a known level of accurracy and reconfiguration is much easier.
If you used a resistor network to convert the currents into voltages, you would be able to measure these voltages with your E-Series DAQ card with no problem. However, in order to convert these voltages back into the original currents you would have to apply scaling within MAX. This would require that you know each of the resistance values. Since many resistors have a slight tolerance, each resistor would likely have a slightly different value and need to be measured individually. The resistors could possibly change value over time or depending on the environmental temperature.
The signal conditioning solution, on the other hand, can provide you with a
known level of accurracy based on the specifications of the modules used. Additionally, if you ever required a change in your design you would only have to modify the configuration in MAX and no hardware changes would be needed since newer SCXI modules are software configurable.

Similar Messages

Measurement Computing DAQ Boards and LV

I have been using LV and NI DAQ boards for several years with
excellent results. Goodby C++ forever (well...).
My boss sent me a flyer for Measurement Computing DAQ Boards and the
prices are great. They even offer a card I can't get from NI.
My question is: how well do these boards work with LV? Can I use all
the NI supplied VI's or must I use only the ones provided with the
Measurement Computing card?
Does anyone sell a card that clones a NI card so all the NI VI's work?
Thanks,
Linuz

Here's an opinion from somebody who doesn't work for NI also...
The measurement computing boards are technically very good, and also very
inexpensive. However the last one (a multifunction DAQ card, I forget the
model number) definately suffered from the SW differences you describe.
I already have enough difficulty getting the NI cards to work properly; for
a complicated project I wouldn't want to add a 3rd party card to the mix!
Usually it's worth a couple hundred bucks to have the full NI-DAQ driver,
support with NI-MAX, standard NI vis, and technical support if (when) the
whole system doesn't work as documented. I have had enough trouble using
RTSI synchronization between genuine boxed NI products. For an ambitious
project I would rarely consider a 3rd party DAQ solution.
On the other hand, if your application is straightforward and you like the
cost savings then go for it. When I tried the computerboards card, the SW
was lackluster but functional. The HW was very solid and around 1/3 of the
price. Given that Labview PDS is so freaking expensive, I would definately
consider a 3rd party board for routine tasks. I had a fine experience with
the computerboards card and the approx $500 savings (at the time) made the
project affordable.
-joey
"Greg McKaskle" wrote in message
news:[email protected]...
> > I have been using LV and NI DAQ boards for several years with
> > excellent results. Goodby C++ forever (well...).
> >
> > My boss sent me a flyer for Measurement Computing DAQ Boards and the
> > prices are great. They even offer a card I can't get from NI.
> >
> > My question is: how well do these boards work with LV? Can I use all
> > the NI supplied VI's or must I use only the ones provided with the
> > Measurement Computing card?
> >
> > Does anyone sell a card that clones a NI card so all the NI VI's work?
>
> Any board can work with LV provided it has a driver to control it or you
> are ready to do peeking and poking to the board. Ideally it will also
> have the DLL calls into the driver wrapped into some VIs for easier use
> by LV users.
>
> Measurement Computing does have drivers, and you can purchase LV VIs for
> their cards.
>
> Before I go on, remember that I work for NI, so feel free to get another
> opinion or look into it yourself, but you will see a BIG difference in
> the SW support for boards from various manufacturers. NI provides lots
> of SW tools, VIs, and tech support, and that is reflected in the price
> of the boards. If a company sells the same board for less, they may be
> providing less in the SW and support side. You and your manager will
> have to determine the overall price of the project based upon your time
> spent installing, troubleshooting, writing VIs, and the price of the HW.
>
> As for a company making a clone of our HW so they can redistribute our
> driver? That has happened in the past, but to my knowledge no boards on
> the market currently do that.
>
> Greg McKaskle
>

Synchronisation of frame grabber and DAQ board

I want to aquire images and analog voltage signals at the same time, and synchronised, using a NI PCI-1428 Camera Link frame grabber and a NI PCI-6014 DAQ board. Can this be done using the RTSI trigger functions? I know that the frame grabber supports this, but what about the DAQ board?
How about synchronising a NI-board with a non-NI frame grabber?
Thanks a lot!
Peter

Hi, Peter,
No, the PCI-6014 DAQ board does not support RTSI. However, most of the low-cost E-series NI data acquisition cards do support RTSI, such as the PCI-6024E or PCI-6036E, so you might consider using one of those boards instead.
If you decide to go that route, there is a useful tutorial that describes the signals that can be routed over RTSI for NI DAQ and IMAQ boards:
Developer Zone Tutorial: Synchronizing Motion, Vision, and Data Acquisition
as well as several example programs:
Developer Zone Example: Integra
ting IMAQ and DAQ with Single Display
Developer Zone Example: Low-level Triggered Ring (with DAQ-supplied triggers)
As for a non-NI frame grabber, that would really depend on what support the frame grabber has for timing and synchronization. You could route a trigger signal or scan clock out over the PFI pins on the PCI-6014, but you would need to see if the frame grabber is designed to receive these types of signals.
I hope that helps!
Best regards,
Dawna P.
Applications Engineer
National Instruments

How to measure the resistnace of wire without any current input by lab view and DAQ-9172

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

Measure Frequency of Digital Signal from DAQ-Board

I'm using a National Instruments DAQ board and I need to measure the
frequency of a digital signal from my data acquisition board.
I know the measure frequency.vi (In diagram - data acquisition -
counter), but i don´t understand yours implementation mainly in input
"counter". Because i don't understand the relationship of board channel (for
signal acquiring ) and the measure frequency.vi.
Thanks in advance,
[email protected]

Hi,
Attached is a vi which models your signal, and provides a way to measure the average frequency over a window of time. It converts the signal to a sequence of periods. I usually start with this approach because you can save the data in a much more compact form if your sampling rate is high. Obviously over a specified period of time, if there are no zero crossings the frequency is zero, so I was a little incoherent before. The real issue is the latency caused by averaging. Your frequency measurement is most accurate half your window size before the current time, so smaller windows give you more up to date measurements, but also more noisy. If you need the most up to date measurement, then you have to use the time since the last crossing which is the case where the frequency never goes to zero. That's probably not a realistic situation. If you needed less latency, you could use a prediction algorithm.
Also, there are a number of signal measuring and processing vi's that LV gives you, for instance pulse measurements that could be used to partially implement this or other approaches, but I normally steer clear of them unless they fit exactly due to having to convert back and forth to the waveform data type.
Have fun!
Attachments:
DigRandFreq.png ‏62 KB
DigitalRandomFreq.vi ‏34 KB

Error -2147220733 occurred at DAQ Assistant (in Measurement and Automation Explorer)

Ok! Just before the weekend I figured out how to make channels in Measurement and Automation Explorer for inputs through a couple different NI input devices (USB-9211A & PCI-6229 DAQ). Things were going well. Loaded up the computer today, added a few more channels. Worked fine. Now all of a sudden, any channel I make has an error and if I try modifying existing channels and saving, I get same error:
"This global channel currently has an error. You can save the global channel, but it cannot be used until all errors have been fixed. Press "Yes" to save anyway, or "No" to cancel and show the error."
If I hit yes, the channel is non functional. After hitting no, I get:
"Error -2147220733 occurred at DAQ Assistant. Possible Reason(s): "
with no possible reasons listed. I tried restarting the program. I tried restarting the computer. I verified connections. Searched for the above stated error number on ni.com, google.ca, and in the MAX help files, and found absolutely nothing. I have no clue what to do. Any help would indeed be very much appreciated.

Hi there,
This is my first time on here and I've only been using this software for a couple of days so it's possible I'm making a trivial error but I thought I'd post here anyway as I can't find anything on the net about my problem.
I also get an error while trying to save:
Error -2147220733 occurred at DAQ Assistant
Possible Reason(s):
Requested Code: -2147220733
But mine comes about in different circumstances to the one in the original post on this thread by Kahless. I was editting a VI logger task and within that I was trying to edit an NI-DAQmx Task. I was trying to change the clock settings, specifically I was attempting to change the Rate (Hz) from the 1k default to just 20, or 200. I got the error while trying to save so changed it back to 1k, but the error persisted even though I'd set it back to what it was.
I thought at first it might be simply that I was trying to edit an NI-DAQmx task within VILogger, so I tried making the ammendment directly but the problem was still there.
Any ideas?
Many thanks.

How to build a current loop with cFP-1808 and analog input module AI-110?

I am trying to build a current loop to measure temperature via and a resistance thermometer a transmitter that converts the signal to current. I am using cFP-1808 with the power supply PS-5 directly connected to it.
For the current measurement I am using AI-110 but I am having trouble with getting current in my loop. I have looked in he manual of the AI-110 module and am using the set up for a "loop with an external power supply", counting the PS-5 as external. That is to say, I have connected the negative transmitter terminal to Vsup on the AI-110, and the positive side to Vin. Now, however, I am stuck. I don't get any signal in my loop.
Can I use the PS-5 to power my AI-110 module or do I need to use another external power supply? In this case, how do I connect this?
Thanks for any help!

Clara G:
I overlooked that in your 1st post you were connecting the other end of the transmitter to Vin, you actually need to connect it to Iin on the AI-110.
Regarding the use of the PS-5 to power the cFp and supply power to the loop, I do not know if that will work or not.
Suggest that you switch over to Iin terminal and use the separate 24V supply to power the loop. If that works, them maybe try the PS-5 for both the cFP and loop power.
-AK2DM
~~~~~~~~~~~~~~~~~~~~~~~~~~
"It’s the questions that drive us.”
~~~~~~~~~~~~~~~~~~~~~~~~~~

I want to run my program with continuous aquisition and write data to file when a button is pressed and get the most recent samples from the DAQ board.

This is an update to a question I asked earlier. I am still trying to solve the problem. I have included a zip file with a library file. The file to open in pj_pushbutton.vi. I have placed comments explaining the issues and problems in this vi and the subvi's.
When I push my button to write the data to file I think it is writing the data that has already been stored in the buffer and writing to file all at once. I want the data that is taken from the DAQ board from the time that I press the Write File button. How do I do this?
Attachments:
pj_pushbutton.zip ‏692 KB

Hi,
1. In AI read, you need to set the Read/Search option to "Relative to End of Data".
2. Next you should not start AI Read VI until you press the Write to File. I am attaching an example VI below. Please see if it helps.
Regards,
Sastry V
applications Engineer
National Instruments
Attachments:
MostRecentAcquiredData.vi ‏97 KB

I want use c++ for NI DAQ board and remote data access(RDA)

how can i control NI DAQ board with c++(bolandc) through network?

This is a forum for Measurement Studio development tools for Visual C++. You should post questions like this to the Measurements->Multifunction IO section of Developer's Exchange.
Best Regards,
Chris Matthews
National Instruments

Encoder and E-series DAQ Board

Hello!
I am connecting a Quadrature Encoder to a PCI-MIO-16E-4 DAQ board. The board is now called a PCI-6040E. I am wondering how exactly to connect the Encoder to the DAQ board. Direction is not necessarily that important, but it would be cool if the DAQ board could tell when the direction changed. On the board are an out, gate and clock. I don't know what to put where??? Please help me???
Thank you,
Tiffany Bierly

CTR0 :
A --> CTR0 SRC (pin 37)
B --> P0.6 (pin 16)
CTR1 :
A --> CTR1 SRC (pin 42)
B --> P0.7 (pin 48)
See chapter 4 of this document for more details about using quadrature encoders with series E DAQ boards.

Speed measure with DAQ and torque transducer

Can anyone tell me how to convert the voltage i get from torque transducer, which can measure torque and velocity eather. I made a program with labview, but it gives me some voltage. I'd like program converts me that voltage to a velocity.
Thanks for answers.

First of all, we need to deeply understand the signals we receive from the sensor.In my opinion, the information from the datasheet is not the most comprehensive
Sensor requires 12V DC, 160mA excitation.
Torque: 0V-10V, -10V-0V depending on direction - should be connected to AI
Speed 60 pulses/rev - should be connected to counter 0
Angle 360 pulses/rev (two signals- angular encoder) - should be connected to counter 1
What I would recommend is you started with LV examples for:
Hardware Input and Output -> DAQmx
Torque - Analog measurements and then scale the signal to result in strains
Speed - Counter Measurements -> Digital Frequency
Angle - Counter Measurements -> Position
Please find the proper example, scale them properly, make each work individually and in the end, integrate the three examples into one single application,
Mircea

Connecting more than one sensor cable to screw terminal to collect more than one signal in single DAQ board channel?

I don't know if this topic is being posted in the correct location. I am new to LabVIEW and the hardware associated with it. I am using an NI 9237 DAQ board for a senior design project in engineering and I was informed that I can make multiple connections to a single screw terminal which in turn will connect to one channel of the DAQ board. To give the specifics, I have two pressure transducers and would like to connect them to the same screw terminal and channel on the DAQ board yet separate them when acquiring data in the VI. Does anyone know how to do this? I know is is essentially knowing what pins do what on the screw terminal but I can't find this anywhere. I am currently doing the job with two screw terminals and two of everything else (RJ50 adapters, etc.). I would appreciate any input. Also, please let me know if I am posting in the wrong board and if possible, which board I should be posting to.
Thank You,
bsteinma

bsteinma,
What you may have heard is that you can measure multiple signals on the same task, not on the same channel. By tying both of these signals to the same channel, both signals will compete to drive the line. The channel on the card will only interpret this garbled signal and you will get no useful data. If you are new to wiring up hardware, I recommend configuring a task within Measurement and Automation Explorer and then clicking on the tab along the bottom of the page titled, Connection Diagram. This will show you what electrical connections to make. Then, in LabVIEW you can read multiple signals (channels) and manipulate each signal how you would like.
As far as boards go, you will generally find an answer where ever you post, but the Multifunction DAQ board is a great place to post when you have questions regarding hardware (like your 9237).
Cole R
Applications Engineer
ColeR
Field Engineer

Acquiring multiple voltage and current sine waveforms, and log them along with the respective time stamp in a file."

"I am doing a data acquisition project using a 16 channel N.I. series 6020E card where I want to capture respective current and voltage sinusoidal signals. I am planning on capturing four pairs of matching current and voltage signals. I planned on taking one reading across the channels every fifteen minutes. This reading will need to be 60 data points per period or 3600 readings per second per channel in order for me to recreate the sine signal to determine the phase angle difference between the voltage and current. I was able to get one channel to capture a signal but could not get more than one working at a time. I am also trying to sycronize the data collection so all samples are with respect to each other. Thanks for any help."
-posted by cappy on 2/11/2002
John N on 2/12/2002 answered:
"Hi Cappy,
Could you post this question to the Hardware > Counter/Timer or Hardware > Multifunction I/O forums? I think you will get more responses there. Here is a link.
The hardware is usually a better differentiation since software can support such a huge range of functionality.
The data rates you are talking about sound reasonable. Are you using the USB or the AT interface?
One other thing to be aware of is that the samples taken will not be simultaneous due to the multiplexed nature of the MIO board measurements. However if you know the channel clock rate(output from one of the VI's), then you can calculate the time difference between each measurement and correct your phase measurements by that amount.
If you have more questions, please post this to the other forum and copy all of our discussion to let everyone know what we have talked about already.
Best Regards,
John Nieri
Applications Engineer
National Instruments"
I am using the USB connection. If anyone can help with or has a similar VI for this, it owuld be appreciated so I can work on the larger aspect of the total project.

The easiest VI to use for this acquisition is AI Acquire Waveforms in the data acquisition palette in LabVIEW. This VI allows you to perform a finite acquisition from multiple channels on your DAQ board. As John mentioned the acquisition from individual channels will not be truly simultaneous. There will be a slight time shift from one channel to the next on the order of the maximum acquisition speed of the card, 100kHz or 10 microseconds in your case. By accounting for this 10 microsecond delay between consecutive channels you can properly calculate the phase shift between voltage and current.
Christian L
NI Consulting Services
Christian Loew, CLA
Principal Systems Engineer, National Instruments
Please tip your answer providers with kudos.
Any attached Code is provided As Is. It has not been tested or validated as a product, for use in a deployed application or system,
or for use in hazardous environments. You assume all risks for use of the Code and use of the Code is subject
to the Sample Code License Terms which can be found at: http://ni.com/samplecodelicense

DAQ Assistant in subvi not updating output to DAQ board with each call...

Hi All,
I am calling a simple subvi that creates a user-defined number of pulses with "Square Waveform.vi." This square wave (with the given total number of pulses) is then used as an input to a DAQ Assistant controlling an analog output signal on a NI USB-6259 DAQ board. I am using Labview 8.5 right now.
However, each time I call this subvi from my main program, the output I measure from the DAQ board is identical to whatever I set in the first call (i.e., if i created two pulses in the first call, I get two pulses on every call, regardless of the input I feed to the subvi). The multiple calls to this subvi are made in sequential frames in a stacked sequence. I believe stacked sequences are frowned upon by good labview people, right? But putting that aside for the moment...
The "#-of-pulses" input I give to the subvi is updated in a subvi front panel number indicator and a graph of this waveform. Just not in the real output I measure from the board. Why is the hardware output being asserted (with the original input value) before this new number can reach the DAQ Assistant?
The sloppy fix to this is just to put that square wave creation code in my main program each time I need it. This does work and fixes my problem. However, I would like to use subvis to keep things clean.
I am not a good Labview programmer, but have used this software for a number of projects and am stumped by this. Any ideas?
Thanks,
John

Hi John,
I am running your code over here and seeing
the same results. I believe the problem is that the DAQ Assistant is
being called inside a loop (really a sequence structure, but
nonetheless more than once). Sometimes it is difficult to troubleshoot
the DAQ Assistant in cases like this--it is trying to be "smart" and
seems to be avoiding re-configuring its parameters inside the loop.
This is intended to improve loop speed for when customers are
performing continuous operations. In this case, it is performing a
finite generation, and the number of samples generated appears to carry
over from one loop iteration to the other.
It sounds
like you have discovered one workaround for this already: putting a DAQ
Assistant in each frame of the main VI. Two other options that come to mind are:
Use the lower-level DAQmx functions inside
the sub VI. Here you will have explicit control over when the task is
created and cleared, and when parameters are set. You can find
examples of how to use the DAQmx API in the Example Finder at:
Help >> Find Examples... >> Hardware Input and Output >> DAQmx
Write
a consistent amount of samples to the DAQ assistant by "zero-padding"
your signal. For example, instead of writing [10, 1010], try writing
[1000, 1010]. In this case, it wouldn't need to reconfigure the number
of samples to generate.
One lesson to take away here is
that the DAQ Assistant is good for basic functionality, but for more
advanced control over the execution and configuration of your task you
should learn to use the lower-level DAQmx functions. In this case it
sounds like the problem is actually a bug. I'll file a bug report, since the DAQ
Assistant is not checking for waveform timing changes even though your
timing is set to Use
Waveform Timing.
Thank you for pointing out this odd
behavior--out of curiosity which version of DAQmx are you using?
-John
John Passiak

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.
I have read in a lot of threads that one can use RTSI lines to retrieve encoder position with a DAQ Board though it is acquired with a Motion board. But there are no examples at all about this.
To sum up, I need to send Encoder Phase A to RTSI0, Encoder PhaseB to RTSI1 (which I already do), retrieve info with a DAQ device and then calculate rpm.
Christophe
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
#adMrkt{text-align: center;font-size:11px; font-weight: bold;} #adMrkt a {text-decoration: none;} #adMrkt a:hover{font-size: 9px;} #adMrkt a span{display: none;} #adMrkt a:hover span{display: block;}
>> "Du 11 octobre au 17 novembre, 2 sessions en parallèle : bien démarrer - approfondir vos connais...

Current loop measurement and DAQ board

Similar Messages

Maybe you are looking for