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Specs are here NI 6034E (page 4)

Sorry my friend but I have to disagree with you. I believe what you are saying is different from what he suggested. From what I understand you suggest not to take into account the gain in this calculation, but take into account the reading of this gain. I believe this is wrong for two reasons: If you take a closer look at the two images that I have posted, you will see that in the first one the range in the DAQ board is ±0.05 (gain=100) while in the second one the range is ±0.5 (gain=10), which means that the accuracy calculator takes into account the gain in the calculation. The calculation 0.001203*0,0588/100+ (100 +5,04)*10-6=0.1057mV (which you told me) is different from the result of the accuracy calculator (0.0018mV) if the input value is as you suggested below So the calculation you suggested me would not be in error by a factor of 100, but it would be decreased by 70mV from what I had calculated. Anyway, I have to agree with you on the thing that this is a "black box" thank you ShauR for you thorough answers, you helped me a lot

That wouldn't be such a bad idea!!!! Ok before I post here I posted in the NI forum (I hope you were not offended because I appreciate your valuable answers) but nobody gave me an answer until I told you before. So he said: Does this answers your question? I hope that you follow this thread because I believe that I will hit back with more questions:D Thank you ShaunR

Someone told me that in order to relate this digitized signal accuracy to the original signal, they divided it by the gain given by the SCXI-1120B module. This is why there is a factor of a 100 difference between the two. Is this correct?

OK! I am trying to calculate the overall uncertainty of DAQ System. I know about the accuracy calculator in the ni.com and I am trying to check my results using this tool. So the calculation formula is: Absolute Accuracy = +/-[(Input Voltage x % of Reading)+ Offset +System Noise +Temperature Drift] In my measurements there is a temp drift, from 29-31°C, but the above formula is for enviroments form15-35°C. So the temperature drift is zero. At first I set to the accuracy calculator: DAQ device to PCI-6034E and SCXI module to none. Then I set for example 0.001203V and Average of 100 readings.The result is the following: According to the E Series User Manual (page 38 gain+resolution PCI-6034E) Absolute Accuracy=0,001203*0,0588/100+ (28,9 +2,75)*10-6=0,03235mV which the same with the accuracy calculator. When I I set to the accuracy calculator: DAQ device to PCI-6034E and SCXI module SCXI-1102B, I do not get the same results about the absolute accuracy of the DAQ device. Accuracy Calculator: Me: DAQ Absolute Accuracy=0,1203*0,0588/100+ (100 +5,04)*10-6=0,175mV which I a very large number. I assume that the input value is 0,1203 because the gain of the scxi 1120b is 100. What I am doing wrong? Sorry my posts are a bit tiresome!!

Thank you for your answer ShaunR. I was mostly interested in the gain part of the scxi and pci6034e that you mentioned first. I have also a couple of questions about absolute accuracy in the DAQ system. Shall i post them here or create another topic?

Thank you for your answer ShaunR, The resolution of PCI-6034E is 16 bit. I know the formula you mentioned. What I really want to know is how the gain is applied. For example i assume I take a temperature measurement at 30 oC. This temp equals with 1,203mV. This input signal enters the SCXI. The SCXI uses the range ±100 mV (gain 100). So the signal will be 1,203mV*100=120,3mV ??? Then the signal is amplified in the DAQ board. If the above is correct then the DAQ board will use the ±500mV (gain 10) Again the signal will be 10 times amplified 120,3*10=1203mV=1,203V? The code width with the above setting will be 1V/216=15,26uV Assuming that I want to calculate what will be the minimun temperature that the DAQ board will detect. For K thermocouples 1oC is 40uV. So if I have ΔΤ=1oC according to the above amplification the 40uV will be amplified to 40mV. So 15,26 (uV)/40 (mV/oC)=0,3815*10-3 oC Please can you verify if the steps of amplifications are correct because I feel that 0,3815*10-3 oC is a very small temperature to detect. Thank you very much ShaunR for your time. Giorgos P

Hallo, I am using K thermocouples and I want to measure temperatures between 30℃ and 60℃ which corresponds to 1,203 – 2,436mV voltage range. I use the following Data Acquisition system: Connector block SCXI-1102B Controller PCI-6034E The specification of the above are: SCXI-1102B has 2 possible input signal ranges: ±10V (gain=1) and ±0,1V (gain=100) PCI-6034E has 4 possible input signal ranges: ±10V (equals gain=0,5), ±5V (equals gain=1), ±0,5V (equals gain=10) and ±0,05V (equals gain=100) I want to know how each device amplifies the signal and what will be the total amplification of the signal, in order to calculate the code width. Thank you very much, Giorgos P

My friend in this occasion it simply will not write the spreadsheet. I do not want this to happen. Instead I want to have control where I can insert number of samples (for ex.1000 samples) and a control where I will insert the rate (for ex. 100Hz). Consequently the vi will run t=N/f seconds. the vi that I have so far runs until I press the stop button. The problem lies in the polymorfic vi's DAQmx Timing.vi and DAQmx Read.vi. If you have time please take a look. Thank you!

Thanks SciWare It really worked. Very peculiar... The strange thing about it, is that if I do not put the append to file=true then i will have the last set of temperatures (!!). Probably because it does not append the previous tempreatures to the file. Instead of putting a constant file path i tried to replace it with a control. The problem is that if the file has not been created then it cannot accept it. Do you know how to make this vi to take finite measurements for example 2000 samples/channel and then stop but keeping the continually updated waveform? If I change the sample clock.vi to from continuous samples to finite samples I won't be able to to watch constantly updated waveform.

Measurements.txtMeasurements(without while loop).txtGuys I really thank you for the help. I have uploaded the vi that I am currrently running on Labview 7.0 platform and i also i uploaded the measurements that I take from this vi when I enable indexing in the loop tunnel. The problem is that i get a lot of zero's(!!!!!) inside the txt file. Please take a look. I simply know that if I delete the while loop and replace the Write to Spreadsheet.vi with the Export Waveforms to Spreadsheet File.vi then only I will read the temperature measurements. (I also uploaded this txt file) However, I do not want to remove the while loop because I won't be able to watch the continuous updating waveforms. How can I deal with this problem? Another problem is that by having a while loop in the block diagram I cannot control the number of samples that I would like to take. The vi will continue to execute until I press the stop button. Is it possible to keep it that way or do I have to replace the while loop with a for loop? (when I replace it with a for loop other problems also arise!!) Finally, I am trying to configure the gain and the polarity from MAX to find the code width and to calculate the accuracy of my measurements, but it seems that they are automatically configured depending on the temperature input range you provide them. Do you knowContinuous Thermocouple Measurements.vi if they can be configured manually? I really appreciate for the time you take to answer my questions. Giorgios Papakonstantinou

I am a student and I would like to take continuous temperature measurements using thermocouples. I am using an SCXI-1000 chassis, an SXCI 1102-B module, an SCXI-1303 terminal block and the PCI-6034E board. I am taking the temperature readings using the Cont Acq Thermocouple Samples-HW Timed.vi. My problem is that i would like to see in the front panel a continuous updated waveform, while in the end concentrate all the samples taken in a txt file. If I place outside the loop the export waveform to spreadsheet.vi then I will onlytake the last measurements. If i place it inside the loop, the vi will ask me in each iteration to save the samples. How can solve it? I have also a of question regarding the Cont Acq Thermocouple Samples-HW Timed.vi. Is it necessary first to adjust in MAX the temperature range that i would like take measures or it is automatically adjusted when I configure the range in the Cont Acq Thermocouple Samples-HW Timed.vi. Thank you in advance Papakonstantinou Georgios export all data after the loop terminates executing