Connecting thermocouple to DAQ board

Hi,
I have a NI USB-9162 with NI cRIO -9215 (DAQ board) and I want to aquire temperature data with a J type thermocouple. I have read (http://zone.ni.com/devzone/cda/tut/p/id/4237#toc2) that you can't just connect the thermocouple to the DAQ board since you need to compensate for the cold-junction. Could someone explain to me how to do this using labview software? Thank you

Hi trishtrishtrish,
I assume you are asking how best to connect to the AI module and how this affects your system. There are three noise sources: the noise of the measurement board, the thermal drift of the measurement board, and the thermal noise of the cold junction measurement. The first two you should be able to get from the specs of the board, leaving the hardest number to estimate being thermal noise of the cold junction measurement.
When you make a thermocouple measurement, your "resolution" is limited by system noise (quantization and random) just as with any other measurement. However, because of the slow nature of temperature measurements, gain and offset drifts with temperature might also be considered noise and hence limit resolution. More specifically to thermocouple measurements, fluctuations in the cold junction measurement caused by changes in the temperature of either the CJ sensor or the actual CJ terminal temperature can also be considered drifts or noise, and further limit the effective resolution when considered over a long time period. NIs TC products, (which you might consider looking into) like the 9211 are designed with very good offset and gain drifts to limit that effect, but the magnitude of fluctuations in the CJ measurement error depend on the thermal characteristics of the installation.
The dominant source of noise (or resolution) in this application will be in the cold junction. Changes in the temperature of the wiring terminals that make up the cold junction will look like measurement noise, and so they will have the effect of reducing resolution. How much noise (or resolution) the you will end up with will depend on (1) how stable the temperature of the cold junction terminals can be kept and (2) over what length of time the signal is looked at. Over a period of hours, it will probably be very difficult to maintain the noise (or resolution). Over a period of one second, it should be rather easier. If we attempted cold junction compensation, the noise (or resolution) of the measurement will be dominated by the difference between the CJ Sensor measurement and the actual cold junction temperature. This should reduce the noise over long terms, but increase the noise over short periods.
If you are looking to make good measurements you will probably just need to build a old-fashioned cold junction terminal block sitting in an ice bath, and use 0 C as the cold junction value without actually measuring anything, then the noise will just be the stability of the terminal block temperature. If the terminal block temperature fluctuates by 0.1 deg C rms, then you would have an additional 0.1 deg C rms of noise. Check here for an image of how the ice bath would look: http://zone.ni.com/devzone/cda/tut/p/id/4218 You could also look into an insulated oil bath with an RTd as a CJ sensor. I've seen both of these techniques working well in the past but feel they can be a hassle to deal and you might be better off by looking into a device designed for thermocouple measurements.
Regards,
Steve

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Attachments:
ADXL202E_a.pdf ‏147 KB

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I have several comments and suggestions:
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1) Open the DAQ card in MAX and Open the Test Panels
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OB0!sc1!md1!3 (note OB0!sc1!md1!3:6 will display channels 3 through 6)
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How to play a wave file through the DAQ board?

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we want to play a wave file that is saved on the harddrive via the DAQ board. Means we want to connect a amp to the analog output of the DAQ to amplify the sound and play it through a speaker.
We couldn't find any VI that does that. Can anybody tell us how to play a wave file, or perhaps even send us a VI that can do that?
Thanks a lot for your help
Martin - Physical Optics Corporation

Hi Martin,
The only example that I could find on how to do this was using our
older Traditional DAQ drivers version 6.9.3. If you're using Traditional
DAQ drivers, the vi can be found here.
The example reads a 8-bit mono .wav file (an example .wav file is included in the .zip file) and writes it to the analog out of your DAQ card. I've updated the
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I hope this helps,
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Message Edited by Paul C. on 08-14-2007 05:47 PM
Attachments:
daqmx_wav_file_to_ao_output.zip ‏27 KB

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Greetings,
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Dear NI-team and board-members,
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what means enums
typedef enum {
       kG0_Up_DownHardware          = 2,
       kG0_Up_DownHardware_Gate     = 3,
} tG0_Up_Down;
and
typedef enum {
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in (nimseries\ChipObjects\tTIO.h) ?
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and I'm writing programm under QNX6 operating system

Hello alexey_3269,
If you want to read a quadrature encoder start with gpctex1.cpp and follow the thread.
I give you my code:
BEGIN CODE
==========
boardGpct->G0_Mode.writeG0_Load_Source_Select(tTIO::tG0_Mode::kG0_Load_Source_SelectLoad_A);
boardGpct->G0_Load_A.writeRegister(InitialCount);
boardGpct->G0_Command.writeG0_Load(1);
boardGpct->G0_Load_B.writeRegister(0);
boardGpct->G0_Load_A.writeRegister(0);
boardGpct->G0_Input_Select.setG0_Source_Select(9); //see above for choices, PFI8=9, 100 kHZ=18
boardGpct->G0_Input_Select.setG0_Source_Polarity(1); //0=CCW, 1=CW
//If using 80 MHz timebase
boardGpct->G0_MSeries_Counting_Mode.writeG0_MSeries_Alternate_Synchronization(1);
boardGpct->G0_MSeries_Counting_Mode.setG0_MSeries_Encoder_Counting_Mode(3); //3 for X4 encoder counting
boardGpct->G0_MSeries_Counting_Mode.flush();
//Enable Input Pins
boardGpct->G0_MSeries_ABZ.setG0_A_Select(9); //PFI8=9,
boardGpct->G0_MSeries_ABZ.setG0_B_Select(21); //PFI10=21
boardGpct->G0_MSeries_ABZ.setG0_Z_Select(10); //PFI9=10
boardGpct->G0_MSeries_ABZ.flush();
boardGpct->G0_Mode.setG0_Gate_Polarity(1); //invert=1
boardGpct->G0_Mode.setG0_Output_Mode(tTIO::tG0_Mode::kG0_Output_ModePulse);
boardGpct->G0_Mode.setG0_Loading_On_Gate(tTIO::tG0_Mode::kG0_Loading_On_GateNo_Reload);
boardGpct->G0_Mode.setG0_Loading_On_TC(tTIO::tG0_Mode::kG0_Loading_On_TCRollover_On_TC);
boardGpct->G0_Mode.setG0_Gating_Mode(tTIO::tG0_Mode::kG0_Gating_ModeLevel_Gating); //kG0_Gating_ModeGating_Disabled
boardGpct->G0_Mode.setG0_Gate_On_Both_Edges(tTIO::tG0_Mode::kG0_Gate_On_Both_EdgesBoth_Edges_Disabled);
boardGpct->G0_Mode.setG0_Trigger_Mode_For_Edge_Gate(tTIO::tG0_Mode::kG0_Trigger_Mode_For_Edge_GateGate_Starts_TC_Stops);
boardGpct->G0_Mode.setG0_Stop_Mode(tTIO::tG0_Mode::kG0_Stop_ModeStop_On_Gate);
boardGpct->G0_Mode.setG0_Counting_Once(tTIO::tG0_Mode::kG0_Counting_OnceNo_HW_Disarm);
boardGpct->G0_Mode.setG0_Reload_Source_Switching(tTIO::tG0_Mode::kG0_Reload_Source_SwitchingAlternate);
boardGpct->G0_Mode.flush();
boardGpct->G0_Command.setG0_Up_Down(tTIO::tG0_Command::kG0_Up_DownHardware); //kG0_Up_DownSoftware_Down
boardGpct->G0_Command.setG0_Bank_Switch_Enable(tTIO::tG0_Command::kG0_Bank_Switch_EnableBank_X);
boardGpct->G0_Command.setG0_Bank_Switch_Mode(tTIO::tG0_Command::kG0_Bank_Switch_ModeGate);
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boardGpct->Interrupt_G0_Enable.setG0_TC_Interrupt_Enable(0);
boardGpct->Interrupt_G0_Enable.setG0_Gate_Interrupt_Enable(0);
boardGpct->Interrupt_G0_Enable.flush();
END CODE
========
I hope this code is appropriate to you.
FV1234

Thermostat control through DAQ board

Hi all,
I am trying to control a DAQ board (Data Translation, DT9816) through LabVIEW. What I am trying to do is to send "one" to one of the output ports when a temperature value falls out of a specific range and send "zero" when it falls within the range. I tried to do that with a case structure. But when the condition is met, computer send "one" to the ports but when it is not met, it did not cease sending "one". I attached the code provided by manufacturer of the DAQ board (Dout Single.VI) Could you please send me an example VI for the implementation of the idea?
Thanks
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Solved!
Go to Solution.
Attachments:
Doutsingle.zip ‏56 KB

Thanks for the reply,
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How can I make the three function work alltogether properly? The three functions are indication of thermocouple reading is in range or not, sending 1 or 0 to the DAQ board and recording data when a specific condition is met.
Thanks again
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Attachments:
code.zip ‏213 KB

Trigger restarts on DAQ board

Hi.
I'm doing data acquisition with a DAQ board, the USB-6251 model. I need something like the sample VI "Acq&Graph Voltage-Int Clk-HW Trig Restarts.vi", except I need the trigger to restart much more efficiently. When I run that sample VI (and my own adaptation which is attached) I can only get trigger rates of about 30 Hz, and trigger that comes in within 30 ms of the previous one is just ignored. I need it to handle trigger rates of up to 1 kHz. Does anyone have any ideas, or is there another way to go about it that will avoid this problem?
Thanks,
Jeremy
Solved!
Go to Solution.
Attachments:
Restarting trigger.vi ‏25 KB

I think to get the response you want, you will have to use your Trigger signal to start generate the correct number of clock signals from a Counter. See example 'Gen Dig Pulse Train-Finite-Retriggerable.vi'
Use Example 'Cont Acq&Graph Voltage-Ext Clk.vi' to actually do the acquisition.
For a test, set up as follows:
Set the Rate/Frequency to the same value.
Set the Number of Pulses/Samples to Read to the same value.
Set the Counter(s)/Clock Source to the same source
For the Gen Dig Pulse Train-Finite-Retriggerable.vi set Counter(s) to ctr0
For the Cont Acq&Graph Voltage-Ext Clk.vi set the Clock Source to Ctr0Out
Run the Cont Acq&Graph Voltage-Ext Clk.vi first and then quickly start the Gen Dig Pulse Train-Finite-Retriggerable.vi
You should see the acquired signal from whatever input you have connected. I was able to do this without changing either example program. Once you see it work, you can combine the two into one vi.
Message Edited by rpursley8 on 07-07-2009 04:19 PM
Randall Pursley

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 :
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Using Labview on a non-daq board device

How would one go about using a device, connected through USB, in labview that doesn't have a daq board? I have a signal monitor that I've managed to get to work with C++ and was wondering if there was a way to integrate it with Labview at all. I hope that makes sense.

If they've provided a DLL then you can use the Call Library Function Node to call the DLL. You should read the chapter in the LabVIEW Help on calling code from external languages. If it's a C++ DLL you may have problems because LabVIEW only supports C DLL, not C++. A common issue is name mangling. If you do a search on the NI site for "DLL name mangling" you will come across several Knowledge Base articles that discuss this issue. Another common problem is that if the DLL uses complex datatypes (such as structures with strings inside, or pointers to complex structures then you will need to write a wrapper DLL that converts simple datatypes that LabVIEW can handle to the complex datatypes that the DLL uses. Again, there is a wealth of information on the NI site on calling DLLs, so a search will yield lots of information.

Not receiving any signal input with LabVIEW SE, USB DAQ board

Hello all, good afternoon.
I am having a little trouble with my DAQ device, I hope that someone will be able to help me.
I'm plugging a BNC pH sensor to a NI USB 6251 M-series board, to try and obtain the electrical response of that particular sensor, measuring the voltage output for each buffer solution (pH 4 and 7). Have 9.2.3 mx (lastest) drivers.
The pH sensor (floating) is plugged through a female BNC plug to the circuit board, signal is going through a signal conditioning circuit (composed by a voltage follower on each of the wires to lower the output impedance of the sensor, and 2 bias resistors from AI+ and AI- connected to AI GND with the board case wired to the power supply ground, as seen in http://zone.ni.com/devzone/cda/tut/p/id/4494)
I'm measuring in differential mode, as I said both wires of the sensor are going through a voltage follower each, and into the DAQ board. The Op-amps are being powered by +-15v as seen, again, in http://zone.ni.com/devzone/cda/tut/p/id/4494
I did take the time to read the manuals and tutorials I found, did quite a bit of investigation over the last few days, and wired the system carefully.
In labview signal express, I choose to take an analog voltage read, and select input range from -500mv to 500mv, because the sensor should output at most -400mv to 400 mv
Now, much to my dismay labview registers in that channel absolutely nothing, only a little noise (~1 mV). I unplug the sensor and realise that whether the sensor is connected or not, it doesn't make a difference in the presented output - it's as if it the sensor wasn't there at all. And yes, I am measuring the correct channel. I tried connecting the wires to different AI channel pairs as well, could be a faulty one, but no success either.
If I plug a voltimeter to the wires that are going into the analog inputs (after conditioning), it measures about 50 mV, which is a lot more than the 1 mV the board is measuring, but a lot less than the ~180 mV I should be measuring with a pH 4 buffer solution.
I know for a fact the problem is not the sensor, and the DAQ board seems to be fully operational.
I think it might have to do with the signal conditioning I'm doing, or some sort of configuration with the hardware of the DAQ board.
So, any idea what I might be missing?
I'm a week behind schedule because of this, hopefully I will find my answer here.
Thank you very much in advance!

Good afternoon.
Yes I have tried all of that. The board responds very well when a flat 5V DC voltage is fed into a channel.
However after much investigation I believe to have found the problem yesterday, it probably has to do with the operational amplifiers I was using. The input bias current was in the magnitude of nanoAmps, while for pH measurements an IBC of picoAmps or less is necessary due to the high impedance of the sensor. This was causing a drift of over 100 mV on my output which is about 2 pH and thus unnacceptable (even though I had the Bias resistors at the input to ground, like suggested in the NI tutorials, but apparently they were not enough to compensate for the high IBC).
In the lab all available op-amps suffer from this, even Instrumentation op-amps like AMP04 from Analog Devices. I still haven't had a chance to acquire new op-amps with the necessary IBC but hopefully it will do the trick. Makes sense since I checked the datasheets for every op-amp in the lab, and they all had IBC around 400 nanoAmps (and none of them worked), while every single op-amp for every pH meter circuit I found have IBC's of pico/femtoAmps.
The sensor I'm using is from AquaMedic, I'm not sure what the model is, but it's a cheap plastic sensor that comes bundled with their pH Computers.
Thank you very much for your input.

Acquire an incremental sensor connected on the 6013 board counter with Delphi5

Hi,
I would like to acquire an angular incremental sensor connected on the 6013 board counter with Delphi5. I search an example of Delphi program in order to acquire the measurement of a such sensor. Is there somebody who wrote a such program and who can send to me an example program which works ?.
Thanks a lot.
Best regards.
Vercors
Bonjour,
J'ai
une machine pilotée par un imposant programme en Delphi 5. Je souhaite
instrumenter cette machine avec un capteur angulaire incrémental pour
déterminer la position et le sens de rotation d'un axe. Je souhaite
utiliser le compteur d'une carte multifonctions telle que la 6013 par
exemple. Je recherche donc un exemple d'acquisition d'un tel capteur
par ce type de carte en langage Delphi. S'il vous plait, est ce que
quelqu'un a déjà réalisé un tel programme et pourrait il m'adresser un
exemple dont je puisse m'inspirer. Un grand merci d'avance.
Cordialement.
Vercors

Bonjour,
Le lien ci-dssous vous explique comment installer des exemples Delphi avec NI-DAQ
How Do I Install Examples for Visual Basic, Visual C++, and Delphi with NI-DAQ?
http://digital.ni.com/public.nsf/websearch/D60BFBC22980F99D862569B6000EF7CE?OpenDocument
En espérant que cela vous aide à construire votre application,
Cordialement,
Benjamin M
NIF

Connecting thermocouple to DAQ board

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