USB 6009 thermocouple noise

I'm using NI-DAQmx 7.5, Labview 7.0, and a USB-6009.
I'm trying to get a more accurate reading from my j-type thermocouple. It is now distorted with noise and jumps rapidly +/- 20 degrees around room temp without any heat being applied. When heat is applied, it climbs as it should but with the same variation. I haven't moved to the labview side of it yet, I'm still trying to get a usable reading in MAX. I have it wired as a differential input with a floating signal source. I've installed 10k ohm resistors for bias current return as instructed. Installing the resistors helped but still leaves me with the readings shown in the attached pic. I've also tried grounding my USB 6009 with no results. Please help. john
Attachments:
thermocouple reading.jpg ‏41 KB

Hi John,
What you are running into is a problem with the actual voltage resolution of your USB-6009. This device has 14-bits of resolution over a minimum range of +/- 1V. That means that the voltage resolution is (1 - (-1))V / (2^14) = 2V / (16384) = 122uV. While this is an excellent resolution for such a low cost USB device, you will still notice problems when trying to make a thermocouple measurement. The reason for that is that Thermocouples make a very small output voltage (see image below).
Common thermocouple types have the following response:
K type: 41 microVolts per degree Celsius
J type: 56 microVolts per degree Celsius
T type: 52 microVolts per degree Celsius
There are a few options for ways to get around this limitation.
Good: You could read the signal in as a voltage and then manually convert that voltage into a temperature. This would be the least accurate method, but it should allow you to average out your signal and then use the Convert Thermocouple Reading.vi to show the voltage as a temperature.
Better: If you want to keep using the USB-6009 to measure thermocouple, what you really need to do is first amplify your signal before you connect it with your device. This should increase your resolution of the thermocouple allowing you to get more accurate temperature specs. This will require some more complex programming to properly scale your measurements, but it will give you more accurate readings for relatively little cost.
Best: Opt for getting a USB device that is designed for taking temperature measurements such as the USB-9211A. This device would give you a voltage resolution of 160mV/2^24 = 9.54 nV! That's over 12500x the resolution of the USB-6009 that you currently have.
Hopefully the above information helps you better understand what is going on and why. If you have any other questions feel free to post them here.
Message Edited by Otis [DE] on 01-13-2006 11:37 AM
Message Edited by Otis [DE] on 01-13-2006 11:38 AM
Otis
Training and Certification
Product Support Engineer
National Instruments
Attachments:
761029-Thermocouple_Voltages.GIF ‏10 KB

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USB 6009 Data Acquisition noise

When I acquire the voltage from USB 6009, It gives some fluctuation/Noise (Please check the image, green color).
What is the reason for that?. How to overcome this noise? One way is averaging, is there any other ways to do or overcome this problem
Could you please suggest me?
Thank you,
Best Regards,
Rathan
Attachments:
Noise.GIF ‏16 KB

Dear Rathan
The correct Terminal configuration depends on if your power supply is floating or grounded. Please have a look at tabel below.
As to the filter, which type of filter to use depends on the frequency of your signal. If your frequency (or frequencies) is low a lowpass with a cutoff frequency a bit over your frequency would be best. Conversly if your frequency is high a highpass with a lower cutoff frequency would do the job. If you are interested in only a single or small spann of frequencies a bandpass could be used.
You can filter your signal either via a hardware filter before you acquire it via your DAQ, but that would require that you have or can build a hardware filter that fits your needs. Else you can filter the signal in software after you've aquired it. The filters in LabVIEW can be found in the functions palette under Signal Processing -> Filters. I think a butterworth filter would do nicely. You can find an example through the LV Help.
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Message Edited by DavidEk on 07-29-2009 05:03 AM
Attachments:
Connection Configs.PNG ‏66 KB

Measuring temperature Via Thermocouple and USB-6009?

Hi,
I am trying to perform temperature measurements using a k type thermocouple and the USB-6009 DAQ. I tried to use the Cont Acq Thermocouple Sample.vi from LabVIEW's example list, but unfortunately I don't know how to fit my DAQ and thermocouple in the vi code. I don't know how to create a thermocouple temperature measurement channel or how to get all the channels in the task, etc.
Any help is appreciated.
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bilbeigg,
It should be noted that the USB-6009 is not well suited for thermocouple measurements. It has 14 bits of precision with a minimum input range of +/-1V, which means it can only detect a voltage change as small as about 122 microvolts. This is much too large a change to get a good temperature reading with most types of thermocouples. Here is a discussion thread on the same topic (Note that the USB-6008 and 6009 are very similar):
http://forums.ni.com/ni/board/message?board.id=170&message.id=294080#M294080
Here is a knowledgebase that explains what you are seeing:
http://digital.ni.com/public.nsf/allkb/8166630BD6965EEA86256FDD0052E89C?OpenDocument
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Message Edited by CMal on 03-12-2008 12:17 PM

USB-6009 Temperature Acquisition

Hi All
I seem to have some brain fade today. I need to use the USB-6009 to with a J type thermocouple. When I hook it up the temperature is not correct and widely varies. I am getting reading from 0 to 60 C at room temperature. I need to incorporate this into another circuit for testing. I assume that I am overlooking the simple and obvious. I have tried using a DAQ Assistant and a DAQmx. Any help will be appreciated.
Thanks
Gerald

Hello Gerald,
You don't have a brain fade! I recently got in a few usb-6009's and am seeing a similar response when trying to measure temperature with thermocouples.
I don't believe this is noise as much as resolution on the usb-6009. At this point I have added resistors to bring down noise but am seeing the same "waver" that you describe (although not quite as extreme). I am looking into building a signal amplifier or alternatively purchasing a TAC80 thermocouple-to-analog converter for use with the usb-6009.
Have you had any progress with your issue?
Adzel

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Hi,
After watching a few Youtube videos, I successfully built a control loop in LabVIEW using my USB-6009. Currently, this loop is limited by the speed my actuator can take and respond to commands, topping out at 200 Hz. This is completely sufficient for my application. My question is more regarding the wasted potential of the USB-6009 to acquire samples at a much higher rate than what would be obtained if I used a simple single sample-on-demand during every iteration of the loop.
It seems to me that having the USB-6009 continuously acquire samples and having my control loop periodically check in for the latest data when it is ready to execute would have the advantage of allowing me to average groups of samples together to lower the overall noise associated with the measurement process (I am reading voltages from an amplified photodiode).
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Howdy Patrick!
Here is a picture of the front panel:
Here is the block diagram:
And I've attached a copy of the VI saved for LabVIEW 7.1.
Regards,
Barron
Applications Engineering
National Instruments
Attachments:
most recent samples.vi ‏73 KB

USB 6009 lock-ups?

Hello,
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See the thread
http://forums.ni.com/ni/board/message?board.id=250&message.id=13722
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Phone (503) 620-3001
Fax (503) 620-6754
www.wavemetrics.com

Usb 6009 digital input

Dear All!!
With the following vi. I'm trying to receive a 5V signal in a digital input, using a usb-6009 device.
I would like to use the 5 VCC supply, available in pin 31 of the same device and send it to pin 17, representing line0 of port0. During execution, 'm physically connecting and disconnecting these pins in order to see the difference in a led indicator. Unfortunatelly, the led is always on, even if both pins are disconnected.
Could somebody help me? I would be very pleased.
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Attachments:
proof.vi ‏38 KB

Hi Miren,
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RTFM?!
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Hi,
I am new to LabView and am having some trouble. I need to input two sine waves into a USB-6009. I have a voltmeter that should read the output. Two of the problems that I have had thus far: I can only use "On Demand" in DAQ Assistant and even when I throw the DAQ Assistant into a while loop I still do not get a readout on my voltmeter. Any suggestions? Thanks for the help.

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Usb 6009 acquisition fall after 15min

Hello,
Like it's said on the name of my post i have some problem with my new usb 6009. When i start it all work good but after a while my two AI fall to 0V. I put my code in joint pieces. I use AI0 and AI1 with a 220ohm resistance.
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Attachments:
test.vi ‏30 KB

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Kudos are welcome

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Hi
I'm pretty new to Labview, so you may have to bear with me. I have a USB-6009 and I want to generate a continuos analog output voltage. I've got the example you have posted 'Gen Mult Volt Updates-SW Timed_LV7.1 (0 to 4).vi' working and it outputs a continuous sine wave.
In a similar manner I need to generate:
1. Ramp up voltage (and ramp down voltage): starting with a continuos constant voltage, which after a period of time linearly increases to another constant voltage, and which allows me to specify the 3 time intervals and the rate of increase.
2. Pulsations: whereby I can specify the amplitude and time interval of each pulsation
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ii. The 'Sinusoidal Pattern' input which seems to generate data for a sine wave- I can't get a description of that and there are no similar VIs for other waveforms; and what is the function of the two numbers it has?
iv. How do I change amplitude and time period for the wave?
iii. What does 'Index Array' do?
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Hi there,
I'm guessing the VI you are using is the one from this KB:
http://digital.ni.com/public.nsf/allkb/6F2C2B49A89D685C8625711D007BDD64
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ii. The sine pattern is just an array constant of doubles that make up the sine wave voltage values, and the for loop adds an offset (of two volts) to every single one of those values. You might want to replace that entire array constant and for loop with a Simulate Signal Express VI (just search for Simulate Sig or look in the Functions >> Input palette) and convert the dynamic data output to an array of doubles. You can configure the type of waveform, amplitude, and time period from that express VI as well.
iii. Refer to previous answer.
iv. Index array returns an element of an array based on the index input. You can turn on the context help and move your mouse over functions to get more help on them.
I hope that helps!
Way S.
NI UK Applications Engineer

Usb 6009 multiple analog inputs

I am currently attempting to sample two different analog inputs at different sampling rates using a USB 6009. I keep getting the 'resource reserved' error and am wondering if this is not possible using this DAQ. Questions:
1. Does creating two analog input channels on the device cause this error?
2. Is it possible to sample at different rates on channels created in the same task? (i am trying to 'slow down' the second analog input to display switch points to a customer)
3. Running multiple analog inputs using independent timing would be better achieved by switching to a higher end DAQ? If so which would you recommend?
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I surf therefore I am....
Attachments:
demo_nolvl.vi ‏27 KB

The DAQ boards only have 1 timing clock for the analog inputs/outputs. So you can only have 1 sample rate on a given card. I would recommend just sampling at the highest of the desired rates in a single task.
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Kchiman,
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Connecting the sensor could be done via screw terminals.... no risc for ppt high performers to touch the solder iron on the wrong side
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Henrik
LV since v3.1
“ground” is a convenient fantasy
'˙˙˙˙uıɐƃɐ lɐıp puɐ °06 ǝuoɥd ɹnoʎ uɹnʇ ǝsɐǝld 'ʎɹɐuıƃɐɯı sı pǝlɐıp ǝʌɐɥ noʎ ɹǝqɯnu ǝɥʇ'

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Hi.
I have created a 4 channel differential data logging scope with a NI USB-6009. I would like to deploy this 'easily' to many of my colegues. I have app builder and the ability to build apps, but I would like to include the correct drivers for the 6009 in with the installer (although I have selected NI_DAQmx Core Runtime and NI_DAQmx MAX config support).
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Hello,
I am attempting to use python (with ctypes) to control my USB-6009. The goal is to write out an analog voltage and then read in the voltage through an analog input with ability to change the number of points averaged and the number of times this is repeated(sweeps) averaging the analog input array. The issue is that as we increase the number of times the voltage ramp is repeated (sweeps) we get a time out error (nidaq call failed with error -200284: 'Some or all of the samples requested have not yet been acquired). This has us confused because the sweeps are in a larger loop and the Daq function should be the same if there are 10 sweeps (works) or 1000 sweeps (crashes). Any insight would be greatly appreciated. I have included the code below for reference.
import ctypes
import numpy
from time import *
from operator import add
nidaq = ctypes.windll.nicaiu # load the DLL
# Setup some typedefs and constants
# to correspond with values in
# C:\Program Files\National Instruments\NI-DAQ\DAQmx ANSI C Dev\include\NIDAQmx.h
# Scan Settings
aoDevice = "Dev2/ao0"
aiDevice = "Dev2/ai0"
NumAvgPts = 10
NumSweeps = 50
NumSpecPts = 100
filename = '12Feb15_CO2 Test_12.txt'
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Samplerate = 1000
StartVolt = 0.01
FinalVolt = 1.01
voltInc = (FinalVolt - StartVolt)/NumSpecPts
# the typedefs
int32 = ctypes.c_long
uInt32 = ctypes.c_ulong
uInt64 = ctypes.c_ulonglong
float64 = ctypes.c_double
TaskHandle = uInt32
# the constants
DAQmx_Val_Cfg_Default = int32(-1)
DAQmx_Val_Volts = 10348
DAQmx_Val_Rising = 10280
DAQmx_Val_FiniteSamps = 10178
DAQmx_Val_GroupByChannel = 0
def CHK_ao( err ):
"""a simple error checking routine"""
if err < 0:
buf_size = 100
buf = ctypes.create_string_buffer('\000' * buf_size)
nidaq.DAQmxGetErrorString(err,ctypes.byref(buf),buf_size)
raise RuntimeError('nidaq call failed with error %d: %s'%(err,repr(buf.value)))
if err > 0:
buf_size = 100
buf = ctypes.create_string_buffer('\000' * buf_size)
nidaq.DAQmxGetErrorString(err,ctypes.byref(buf),buf_size)
raise RuntimeError('nidaq generated warning %d: %s'%(err,repr(buf.value)))
def CHK_ai(err):
"""a simple error checking routine"""
if err < 0:
buf_size = NumAvgPts*10
buf = ctypes.create_string_buffer('\000' * buf_size)
nidaq.DAQmxGetErrorString(err,ctypes.byref(buf),buf_size)
raise RuntimeError('nidaq call failed with error %d: %s'%(err,repr(buf.value)))
def Analog_Output():
taskHandle = TaskHandle(0)
(nidaq.DAQmxCreateTask("",ctypes.byref(taskHandle )))
(nidaq.DAQmxCreateAOVoltageChan(taskHandle,
aoDevice,
float64(0),
float64(5),
DAQmx_Val_Volts,
None))
(nidaq.DAQmxCfgSampClkTiming(taskHandle,"",float64(Samplerate),
DAQmx_Val_Rising,DAQmx_Val_FiniteSamps,
uInt64(NumAvgPts))); # means we could turn in this to continuously ramping and reading
(nidaq.DAQmxStartTask(taskHandle))
(nidaq.DAQmxWriteAnalogScalarF64(taskHandle, True, float64(10.0), float64(CurrentVolt), None))
nidaq.DAQmxStopTask( taskHandle )
nidaq.DAQmxClearTask( taskHandle )
def Analog_Input():
global average
# initialize variables
taskHandle = TaskHandle(0)
data = numpy.zeros((NumAvgPts,),dtype=numpy.float64)
# now, on with the program
CHK_ai(nidaq.DAQmxCreateTask("",ctypes.byref(taskHandle)))
CHK_ai(nidaq.DAQmxCreateAIVoltageChan(taskHandle,aiDevice,"",
DAQmx_Val_Cfg_Default,
float64(-10.0),float64(10.0),
DAQmx_Val_Volts,None))
CHK_ai(nidaq.DAQmxCfgSampClkTiming(taskHandle,"",float64(Readrate),
DAQmx_Val_Rising,DAQmx_Val_FiniteSamps,
uInt64(NumAvgPts)));
CHK_ai(nidaq.DAQmxStartTask(taskHandle))
read = int32()
CHK_ai(nidaq.DAQmxReadAnalogF64(taskHandle,NumAvgPts,float64(10.0),
DAQmx_Val_GroupByChannel,data.ctypes.data,
NumAvgPts,ctypes.byref(read),None))
#print "Acquired %d points"%(read.value)
if taskHandle.value != 0:
nidaq.DAQmxStopTask(taskHandle)
nidaq.DAQmxClearTask(taskHandle)
average = sum(data)/data.size
Thanks,
Erin
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USB 6009 thermocouple noise

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