USB-6341 and Temperature Measurement

Has anyone been able to measure temperature using thermocouples connected to the USB 6341? I have been told the unit does not have CJC, which is surprising to me. From what i see, there exists significant thermal variation when measuring temp with ta 6341. Has anyone come up with a method of using a thermocouple or RTD with a 6341 to measure temp?
Thanks,
Erik

I use the USB 6251 and 6351 to measure thermocouples all the time. There is the issue of the dissimilar metals at the device terminals adding to the measurement so you have to keep the box iso-thermal but that's not a big problem if you're careful. I usually just set the CJC to CONSTANT (25C) but you can dedicate an extra TC to compensation and stick it in a cup of ice water to get better accuracy. You still may not get the accuracy of dedicated TC interfaces but it's good to a degreeC or so and does very well indicating the relative difference between two channels. Wire up a couple TCs and test it out in your own lab before you trust anything though. Environmental noise can be problematic, especially with long wire runs.
Using LabVIEW: 7.1.1, 8.5.1 & 2013

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Which board is good to produce 5v TTL and temperature measurement?

I want to use Labview to control a valve controller,which contects 6 solenoid valves. This instrument accepts 0-5V TTL signals. I need to switch the valves on/off below 1 second. Which Ni board is good for this application as well as temperature measurement I want also?
Thanks a lot for your suggestion.

Sheng,
One of National Instruments E Series multifunction DAQ devices should provide all of the functionality you require. You may want to also consider using SCC signal conditioning for your temperature measurements. With regards to the digital output, you will want to verify that the current drive provided by an E Series device is great enough to control the valve. If it is not, the NI 6509 digital I/O device provides high current drive. Below, I have included links to the appropriate product pages:
E Series Multifunction DAQ
SCC Signal Conditioning
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Spencer S.

Recording Temperature and Voltage measurements using Keithley 2182 Nanovoltmeter

Hello all,
I am relatively new to LabView and looking to extend a vi I am currently using.
I am trying to record voltage and temperature measurements from a Keithley 2182 nano voltmeter using a GPIB cable. I have a vi that can do this for either voltage or temperature not both. At the moment I only record what is shown on the display of the nano voltmeter.
Could somebody explain how I could get labview either to change between voltage and temperature on the nano voltmeter or whether it is possible to have two simultaneous measurements of temperature and voltage and how I would achieve this.
Thanks
Mike

Hi,
For each read, no matter Temperature or Voltage there is a certain command that is send to the voltmeter.
I don't think (actually I'm pretty sure) you cannot read it in parallel but you can do it successively: One read Voltage, one read Temperature and so on.
There should be something like:
while not STOP do
1. send GPIB command for changing Keithley to Voltage Measurement
2. send GPIB command for Voltage Read
3. read GPIB -> Voltage
4. send GPIB command for changing Keithley to Temperature Measurement
5. send GPIB command for Temperature Read
6. read GPIB -> Temperature
end
You can take a look in VI to see which are the commands send for Voltage and Temperature reads and to mixed them like I described it above.
If you don't manage it share your VIs (for temp and volt.) maybe it will be easier for me (or something else) to give you some additional advices.
Paul

RTD Temperature Measurements using LabView 2013 and MyRio

Hey everyone. I am VERY new to LabView programming and working with a MyRio. I need to figure out how to measure the resistance of a 2 wire RTD to find a temperature utalizing the MyRio and LabView. I am pretty lost on how to do this. Does anyone know some good resources for making the LabView program off of the tops of their heads? I've figured out how to measure from specific pins, but I am not sure how to get it to constantly output a voltage from the output pins.
Eventually, I would like to have it display the temperature as well as have it turn on or off a heater depending on that temperature, but that will come far later in this process. First things first, how do I take temperature measurements utalizing LabView 2013 and a MyRio with a 2 Wire RTD.
Thanks so much!

Hi JoshEpstein87,
The myRIO can't acquire a change in resistance directly, so you'll need to somehow convert the change in resistance to a change in voltage. There are multiple ways to do this, but you'll need to build an external circuit and then read the voltage output with the myRIO. One example of a circuit that allows you to do this can be found here. To output a voltage on the analog output pins, you should just need to set the output voltage and then it will remain at that voltage until you change it or power cycle the myRIO.
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http://www.ni.com/myrio/setup/getting-started/
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Best Regards,
Matthew B.
Applications Engineer
National Instruments

Software differences between USB-6229 and USB-6341 A/D boards?

I am writing code for a treadmill for wheelchair users. We are doing research with users of manual wheelchairs, and this second unit is very important for the clinic where we work. My OS is Windows 7. The Visual Studio is version 2008 (MS Visual C++ 2008).
The code is fairly well developed and has been running for 2 or 3 years on the USB-6229 DAQ board. We have built a second unit, and the people who built it tried to save a little money by purchasing a USB-6341 board (money is very tight in our research clinic, and it saved them about $1000). We were assured by NI customer service that the software would run with no changes on this slightly different board. The Analog outs and digital outs work great with this new board. However, I cannot read the analog inputs correctly. I do block reads where I read back 10 samples from 8 channels with a simple DAQmxReadAnalogF64 read. The data I get back is interesting. 2 of the channels are returning 0 or 1. 2 channels seem to have a relationship to what is going on, but is not at the right amplitiude. and the other 4 channels just have a slowly decaying signal. I have checked all 8 Analog inputs using NI Max test panels, and the A/D card is returning the correct data to NI's test panel software.
Any suggestions would be greatly appreciated!
Thanks!

Hi,
The programming for the 6229 and 6341 should be very similar, as both cards use the same DAQmx functions. You mentioned that you tried using MAX Test Panels, did you get the completely correct data when you were using the Test Panels? Also, does this codes still work with the USB-6229? Are you using differential, RSE, or NRSE connections?
Evan S.
National Instruments

Measuring voltage and temperature

Hallo,
I've got the problem of measuring voltage and temperature simultaneously, with diferent numbers of samples. I want to use two of the "DAQmx write", but then the error "The ressource is reserved" appears.
Software: Labview 8.2.
Hardware: NI cDAQ - 9172
NI 9211 (Temperaturecard)
NI 9201 (Voltagecard)
How can i fix it?
Attachments:
Fehler.JPG ‏89 KB
Fehlerbeispiel.vi ‏27 KB

Hello LochiMD,
there are sereral things you have to care about.
The best would be, you have a look on the following link:
Synchronize continuous Acquisition of Multiple Analog Input Devices
https://decibel.ni.com/content/docs/DOC-12182 (Have a look on the picture, especially left side)
You should use the VI DAQmx Timing (Sample Clock), samples per chanel and sample mode is necessary.
If you do this, your program should work.
Best Regards,
Nina

Usb 6341 counter number of buffer

Hi
I will use usb 6341 to measure digital pulse.
What is maximum buffer when i use 25Mhz sample clock with buffered mode?
(It shown error when i set 25Mhz clock, N sample mode, 1M sample)
Is there any fast edge measerement with usb 6341?
(I want ns time scale with long time)
Thx

25 MHz is a very large sample rate for a counter... can you elaborate on your application? There really shouldn't be any reason to sample the counter this quickly. If you're trying to timestamp your external pulses with the highest possible precision, I would instead use the external pulse as a sample clock and count the internal timebase (assuming the external pulse isn't also 25 MHz...). Doing this would actually get you 10 ns resolution (instead of 40 ns that you are hoping for with a 25 MHz sample clock) and the required throughput would be based on the rate of your external signal (which is presumably less than 25 MHz, which is the highest frequency that you can connect through the PFI lines anyway...)
To answer your question though...
The on-board FIFO is 127 samples per counter. If your task is measuring more samples than this, you would need to be able to read data off of the device at least as fast as it is coming in. On USB that is going to be highly system dependant (one benchmark here reported 8 MHz). If you really need the higher throughput you are asking for you will probably want to switch to the PCIe version of the 6341 (20 MHz on a single channel mentioned here, I'm not sure if higher rates were tested but I wouldn't be surprised if 25 MHz is sustainable as well).
Best Regards,
John Passiak

SCXI with USB-6341

From a hardware standpoint, can a USB-6341 be used to capture data from an SCXI chassis (ignoring the connector/wiring situation)? I would like to use this scenario and program in C++ but the device access is controlled through MAX and MAX doesn't allow the USB device to be selected as a chassis communicator. It is my understanding that M-series USB mass terminated devices could be connected to SCXI so I'm wondering if it is just a list of compatible devices MAX uses and the USB version of the 6341 isn't on the list for whatever reason (which I would be curious to know).
In this note mass termination is called out specifically (for the M-series USB). What is the difference between mass termination and the wiring pin to pin?
I realize I can communicate with the SCXI in other ways but going through MAX would be much simpler for me (especially for calibration/troubleshooting) and I could use the NI provided DAQmx C examples.
Thank you

Unfortunately this is for work I do at home so I'm in the usual predicament of having to spend more time doing things myself where I can't afford to do it otherwise. I thought the device did have the APFI capability when I purchased it. Accuracy isn't a concern for me because I just need to see the signals (for example: high channel count temperatures where most devices are +/- 1°C on the spec sheets and I just need to know if heat transfer is working properly). I am trying to move away from a DAQcard that I was using for the SCXI to something USB that I can use with any computer in the future.
By the way, I'm only using bare wires inside the X-series enclosure. The cable is an EPM cable and I wired everything per the pinout diagram provided by NI for that cable. The BNC breakout I have wired to the SCXI chassis was working properly so I assumed it was good to go but couldn't get the device to show in MAX. Now I realize it is just the feedthrough on the 1349 that is working and communcation with the chassis won't work.
Thank you

Using USB 6341 device for frequency generation but level is droped when conect

i am using USB-6341 Daq Device for frequency generation. The desired frequency is generated correctly but when i connect to other device the voltage level i means the Peak to Peak voltage of the frequency dropped to 0.6, 1 Volt and also the frequency fluctuated. As I disconnect it from the load or the device the frequency becomes constant and peak to peak voltage becomes 5.
Please some help me to resolve my problem.
Thanks
Best Regards
Naseeb
Solved!
Go to Solution.

Hi Nasib,
I just wanted to clarify a few more things. Can you answer the following questions?
What frequency are you trying to generate?
When there is no load connected do you see the desired frequency?
When the load is connected, does the frequency always change to the same value or does it fluctuate within a certain range? If it fluctuates, what is the range?
Also, what microcontroller are you using?
Can you provide any images?
Regards,
Travis Ann
Applications Engineer
National Instruments
Applications Engineer
National Instruments

DAQ vi to perform digital write and read measurements using 32 bits binary data saved in a file

Hi
DAQ vi to perform digital write and read measurements using 32 bits binary data saved in a file
Two main
sections:
1)
Perform
write and read operations to and fro different spread sheet files, such that
each file have a single row of 32bits different binary data (analogous to 1D
array) where the left most bit is the MSB. I don’t want to manually enter the
32 bits binary data, I want the data written or read just by opening a file
name saves with the intended data.
      2)
And
by using test patterns implemented using the digital pattern generator or build digital data functions or otherwise, I need to
ensure that the
            binary data written to a spreadsheet file or any supported file type
then through the NI-USB 6509 is same as the data read.
I’m aware I can’t use the simulated
device to read data written to any port but if the write part of the vi works I
‘m sure the read part will work on the physical device which I’ll buy later.
My Plan
of action
I’ve
created a basic write/read file task and a write/read DAQ task for NI USB 6509
and both combine in a while loop to form a progress VI which I’m confuse of how
to proceed with the implementation.
My
greatest problem is to link both together with the correct functions or operators
such that there are no syntax/execution errors and thus achieve my intended
result.
This
project is one of my many assignments for my master thesis, so please i’ll
appreciate every help as I’m not really efficient with LabVIEW programming but
I prefer it because is fun and interesting if I get to know it.
Currently I’m
practicing with LabVIEW 8.6/NI DAQmx 8.8 Demo versions and NI USB 6509
simulated device.
Please see
the attached file for my novice progress, thanks in
advance for the support
Rgds
Paul
Attachments:
DIO_write_read DAQ from file.vi ‏17 KB

What does your file look like? The DAQmx write is expecting a single U32 value, not an array of I64.
Message Edited by vt92 on 09-16-2009 02:42 PM
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If bought NI USB-6800 device, is Measurement Studio free for dev?

If bought a NI USB-6800 device, is Measurement Studio free for VC++ development?
Do I need to buy the Measurement Studio license?
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Plus I noticed that there are UNIX/Linux drivers about NI USB-6800 device, but there is no document about C/C++ development under UNIX/Linux!
Can I do the development with NI USB-6800 device under UNIX/Linux?
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Medhi wrote:
Unfortunately it is in windows. Windows doesn't recognize the device. I don't know, is this a problem because of running WinXP in Mac?
That may well be the problem.
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Is it possible to maintain the last AO value after the DAQmx task is done on device DAQ USB-6341 ?

Hi all,
I use the device DAQ USB-6341 to generate the desired voltage waveform by the "finite samples" sample mode.
I notice that the channel resets to zero volts after the DAQmx task is done and the DAQ USB-6341 does not have
the property AO.idleOutputBehavior to select "Maintain Existing Value".
How can I maintain the last AO value after the DAQmx task is done on device DAQ USB-6341 ?
Thanks.
Godel

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Help needed with temperature measurement

hi guys
I need some help with temperature measurement. I've got a NI PCI 5229 card and a powertransmitter. The power transmitter is programmed to output a 4-20mA (0°C - 100°C) signal. How can i get labview to convert this mA signal to displaying it as temperature? Please include a lot of detail as I am a first time labview user.
Thanx

Hi Jaco,
calculate gain and offset for your values. After you have this values, you can calculate your temperature. See the attached picture.
Hope it helps.
Mike
Message Edited by MikeS81 on 05-18-2008 02:44 PM
Attachments:
Unbenannt1.PNG ‏30 KB

Temperature measurements display incorrectly after opening a project.

Dear All,
I am having some difficulty in setting up LabView SignalExpress version 5.0.0 to display RTD temperature measurements from the NI9217 module and the NI cDAQ-9178.
I have two problems:
1. I cannot set the waveform chart to show the desired time interval; I need to set the time interval displayed on the chart to 30 minutes. This means that before taking 30 minutes of continuous measurement the user would see a fixed grid with fixed time boudaries and the plot moving from the left hand side of the screen to the right hand side of the screen. After thirty minutes of measurements have been taken, the chart would begin to "scroll" so that the earliest measurements move off the screen and the chart still displays the time interval of 30 minutes.
2. I need the chart to display correctly immediately after the project has been opened; When I open the project and click the 'run' button, the windows are all displayed correctly but the readings are not displayed correctly, the chart only displays one short line to the right of the screen and a very short time interval of less than a second. I can correct this by changing to a Time XY Graph and then back to a waveform chart but need this to display correctly as soon as the software is opened. The incorrect and the corrected chart are shown below:
The chart below is displayed when the software is opened and the run button is clicked. This chart style is incorrect because the temperature line is displayed in the bottom right of the chart and only for a short time interval.
The chart below is closer to the required graph described in point 1 but I cannot set the time interval to stay fixed at 30 minutes, nor can I make the software display the graph like this on opening, I always have to switch to a different chart type and then switch back to a Waveform chart to replace the format above with the format below:
Any help would be appreciated,
Thanks,
Matthew

Hi Matthew,
We should be able to used this function to save the graph settings as well. I have just tried it on my system and got it to work. the procedure I undertook was:
Open my Signal Express Project
Turn off x-axis auto scale (Right click on graph >> X Scale >>Auto scale)
Enter Properties (Right click on graph >> Properties)
Select the scales tab
Select 'Relative To' under the Timestamp Type.
Set the min as 0 and the max as 1800...Press OK
View >> Layouts >> Make Current Project Layout Default
Save
In this case I used the Relative Timestamp Type but you can use whatever time stamp you wish. When opening up this project after doing this the graph is formatted as required immediately.
Let me know how you get on with this.
Regards,
Aaron. E
Applications Engineer Team Lead
National Instruments
ni.com/support

Encoder Position and Velocity Measurements and Force Measurements

Hi,
I am using a USB 6210 DAQ Card and an optical encoder and force transducer together in an MRI room to measure the power ouput of a patient pedalling on a recumbent ergometer. I would like to obtain synchronous measurements and output this to file. I have started working on the code for the encoder. I am struggling to get the frequency measurement and encoder position outputting fast enough. Any idea why this is? For the force measurements will this be with the same configuration just adding Vi's for analog input. Also I know using the write to measurement file vi is quite slow to write to a spreadsheet what is the more efficient method for doing this.
Regards,
Darren
Attachments:
Angular_Position and RPM.vi ‏46 KB
Angular_Buffered.vi ‏80 KB

Hello Darren,
The fastest file to write to in LabVIEW is a binary file. The specific file type used by LabVIEW is the Technical Data Management (TDM) file. The TDMS file is a version of this file specifically designed for streaming applications. You can find several examples of writing to this file in the NI Example Finder (Click Help -> Find Examples). By using the search tab, you can use the keyword “TDMS” to search for all of the examples that use the TDMS file type. The example Cont Acq&Graph Voltage - Write Data to File (TDMS) can be found from the search tab, or by using the path Hardware Input and Output -> Analog Measurements -> Voltage. While the data acquisition part of this example pertains to analog input, the same file input structure can be used with your counter input tasks.
What do you mean that the encoder and frequency measurements are not fast enough? Each rising edge of the sample clock source will latch the current value of the measurement into the FIFO and transfer this value into the buffer. At this point, how quickly you can read the buffer will affect how quickly the user is updated with the newest measurement information. Since you have specified the number of samples to read in your buffered example, the read VI will wait until that many samples are available in the buffer before returning a measurement (this could slow down the update rate for the user). By specifying -1 as the number of samples to read, you will read all available samples in the buffer. If there are no samples available, nothing will be returned, but the VI will continue to execute. Hope this helps.
Regards,
Browning G
FlexRIO R&D

USB-6341 and Temperature Measurement

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