In NI 6250 common mode voltage

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• How to limit the voltage common mode for the switch

  The user manual mentions a maximum of ±12V ground for my switch (pxi-2536) but I do not see an entry in the field on the pinout of the connector. If I have a floating supply, should I connect the ground to the chassis on the ground on the back of the PXI? Is there a better way to limit the common mode voltage?

  Thank you specify, it makes much more sense!  The best way to go about this that seems will be grounded to the negative terminal of your power supply to ground the chassis security, as I think you suggested at the beginning.  I don't know what frame you have, but you should be able to find a "Reason for connection security" section in the manual. For example, here are the 1044 chassis manual, with the present article is on page 2-4. http://www.NI.com/PDF/manuals/371360a.PDF

  This should take care of it and avoid Earth loops!

• Clarification and Confirmation on the practical Implications of common Mode on differential measures voltage

  Hello people,

  I've read several documents on the site OR about the premium over common measures of mode and I think I understand, but I'm looking for confirmation through two examples (please).

  Both examples assume a data acquisition card OR with +/-10V inputs and a maximum operating voltage of + / 11V (e.g. PCI-6052 with programmable gain 0.5).

  Example 1: Suppose a DC voltage with two resistors divider and a differential input on the daq card configuration.  First resistance = 4 Ohms connected to 100VDC, second resistance = 96 - grounded (0) Ohms.  This results in a decline of 4VDC to the terminals of the first resistance.  However, I believe that the differential voltage of 4VDC may be connected directly to the daq card because the absolute voltage (i.e. common mode?) is in fact 96VDC to 100VDC which is outside the "working range' of + / 11V for the card.  This conclusion is correct?

  Example 2: Suppose a differential measure between two AC signals and a differential input on the daq card configuration.  First report = 25v@0deg, second signal = 10v@180deg.  Some documents on the Web site of NOR, I gathered that the common mode voltage is the average of the vector representation of the input signals.  In this case, it would be (25v@0deg + 10v@180deg) / 2 = 7.5v@0deg.  I think that this signal can be directly connected to the daq card because one of the signals (25v@0deg) is outside the range of the card work (even if the result "means vectors" is within the scope of the map daq.  This conclusion is correct?

  Thanks in advance for any help,

  chassan

  Chassan,

  You're right both of your examples. Is the best way to look at that is that even if you take a measure differential the maximum voltage you can submit a single channel to the + / 11V to the 6052E. Hope this clears things up a little bit.

• define 4461 common mode dc offset

  Hi all

  Anyone know if it is possible to programmatically set a common mode DC offset to the differential output of a 4461 or what should I do with the external components? Please note that this is a different condition to define the differential DC level, which I know you can do.

  Thank you

  Nick

  Hi Nick,

  Thanks for the question. Currently, we do not allow the user to directly set the offset of common mode of production. Bonus mode, both positive (BNC Center) output and negative

  (Shell BNC) outputs have 2.4 KOhms to land (it is not isolated from the Earth). For this reason, in all cases essentially, regardless of the components you will introduce to the common mode

  offset of the output will also present an error of differential gain as well. In addition, due to the lack of insulation, there a limit to how much common-mode offset can be driven out of the ground.

  It also depend on the size of your output signal. When you approach the limit, there will be a significant increase in distortion that will run at full power eventually.

  I hope this helps answer your question.

  -Larry

• 9214 OR problem with a common mode error

  Hey,.

  I take readings using thermocouples type k using the NI 9214 module in a cRio.  System works very well at room temperature, but once I take the surroundings up to 300 ° C thermocouple, I get the error message: "a common mode error has been detected."

  I use the NI 9214 mode high resolution, with disabled OTD.  I went through the documentation on the error, but it is light on the proposed solutions.  I wonder if anyone else has seen this, and if so, how you solved it.

  Thank you!

  Hey GiantDeathRobot,

  Thanks for the reply! It was very useful.

  Let me start with additional information about my setup.  I use a k type thermocouple in a vacuum chamber to measure stuff inside.  I have the NOR-9214 in a just plug cRIO of data of the current temperatures.  Thermocouples are unshieleded in the room, but are exposed to the end inside the room.

  Your comment to the ground made me think that there might be a problem of noise EFM.  So I solved my problem in a weird Garland.  I had the commune for the NI 9214 connected to the nut of the common leg of the connector.  I added a ground cable from the power strip that I use to power all of the components of the House (including the cRIO) cRIO chassis.  This completely clears my noise problem.  I thought I'd follow upward, in case anybody out there is struggling with this as well.

• 'TV most common mode' which is used by film festivals?

  Hello, from below, is there a standard for this?  4 x 3?  16 x 9?  All my images were shot in 16 x 9...

  Thank you

  Matt

  

  Matt,

  I would guess that Widescreen took over the standard, but that is only a guess. Each festival will probably be a sheet of standard, and I ask that, for each, in which I had an interest.

  Now, the key is to shoot what is the most common and edit it directly. Then, if there are others, with different needs, maybe a plan on how you want to manage the other images - Letterbox, pillarbox, Pan & Scan, etc.

  At some point in the future, Standard and widescreen will be moot, as well as BY. Until then, there's always a can of "scary to ' out there.

  Good luck with the festivals and please let us know the percentages of each format.

  Hunt

• constant output voltage DAQ NI PCIe-6321

  Good evening

  I am trying to output a constant tension there 10V DAQassist.
  However, as far as I know, when I want it to generate signals, it will only display waves.

  I'm relatively new to labview and can not fully use the modules of the individual drivers for DAQmx.
  Currently I use an external voltage source to power a set of scales that I'm trying out signals in LabVIEW.
  I've been somewhat successful, but a cleaner set would be to get an output of data acquisition to fully integrate the system
  I know that traditionally deplete you a game recommended by, OR like this:
  http://www.NI.com/white-paper/7138/en/

  However, I work with hardward existing on a limited budget.
  I have an acquisition of data NI PCIe-6321, with a block of connection BNC 20990.
  So, I work with BNC connectors.

  Change the AO writing single-channel > sample > DBL. That should give you a single value whenever you call the VI of Scripture. Also change the entry of data in a single digital control. Maybe call it voltage or something like that? You can probably remove the synchronisation screw DAQmx and the node property Regen as those who will be most relevant.

  A cell of 700 ohm load will draw 10 ohms = 14.3 V/700 mA, which is still well above the 5 limit my AO lines.

  A load cell is wired as a bridge. It is the equivalent of two voltage dividers. Without load on the output of the cell the two lines have equal tension: 5.00 V. When you have a 20 mV out of load cell tension on the two output lines will be 4,990 V 5,010 V (or 5,000 V and 5,020 V, according to the internal configuration). So your 6321 must be configured to accept 5,020 V (plus a bit of noise, mistakes and overload conditions). So, you will need to set it to 10 V range. On the 6341 (I happen to have the factsheet - the 6321 is probably very similar) which means a +/-10 V rank. Which translates a theoretical resolution of 0.3 mV. The output 20 mV full scale of the load cell, it comes down to resolution of 6 bits (6: 16).

  Two possible ways to improve: 1. use a preamplifier or a signal conditioner to amplify the 20 mV at a few volts. These usually have the differential amplifiers to reject common-mode 5 V. voltage They can also have hardware filters.

  2. use a power supply excitement split so that the load cell is excited by the + 5V and - 5V. This puts the common mode voltage to ~ 0 V and you can use the +/-0.2 V rank on the lines of HAVE it.  The resolution is then about 6 uV and the effective resolution on your signal is approximately 11 bits.

  Lynn

• Playback issues of Thermocouples a 9214 in EtherCAT 9144 chassis

  I have an SMU-1078 chassis with an SMU-8135 controller and chassis EtherCAT 9144 with multiple C-modules, including a couple of 9213 9214, running Veristand 2014 and 2014, inertia. I updated last week so I think I have the latest updates for the hardware and software.

  The problem I encounter is that I can read my Type K thermocouples with Thermocouple 9213 modules, but when I connect them to the Thermocouple 9214 module, I see only TC0 change and the rest of the TC 9214 channels are 0 ° c. tried to use high speed and high resolution modes, but no difference. I also moved the module in slot 8 in the EtherCAT chassis, also without success. Then I moved the 9214 with its connector and thermocouples to another machine with a chassis cDAQ in 9188XT and I have read all the thermocouples with NI MAX. This proves that the module is working and that the module connections are good.

  I need to use the 9214 because of his ability to handle the higher common mode voltages. I need help. Please, I beg you.

  Thank you in advance

  Richard

  It ended up that I had to download the last update, 14.0.1 for the NOR-RIO. This solves the problem. I did have to reinstall Veristand, Labview, or any other driver.

  Thank you very much for your answers.

• SCB-68 AIGND vs AIGND

  Hello

  I apologize for the enigmatic title, but I'm a little confused on the difference between the screws AIGND fastons (67, 32, 64, etc.) and the AIGND on the area on the conditioning of signals of PCB SCB-68 box.

  I'm trying to accurately measure a signal 0 - 10V on analog channel 1 mode differential.  I followed directions (see link) connection for differential measurements by adding resistors of polarization on the sign (+) and (-) entered to AIGND pin # 67.  With this configuration I sometimes see saturation in my measurements because of the high common-mode voltage.  I then withdrew my PIN # 67 AIGND polarization resistors and added resistances of polarization in the region (RC14 and RC15) as suggested in figure 5-1 conditioning of signals of PCB and my measurements seems correct and do not saturate.  It seems to me that these two should be the same, but I get different results.  Measures of resistance between screw AIGND fastons (67, 32, and so on) to the AIGND showed high impedance which suggests that they are not the same conditioning of signals of PCB.  All my switches are assigned to the default settings.

  What is the difference between the two AIGNDs, and that AIGND should I use?

  SCB-68 68-pin shielded connector block the user manual:

  http://www.msm.cam.AC.UK/mechtest/docs/scb68%20Manual.PDF

  Material:

  PCI 6221 M data acquisition card

  SCB-68 interface

  Best regards

  HV

  HV:

  These two AIGND are connected inside the data acquisition card, it will appear an impedance high unless the SCB - 68 on the DAQ card.  I measured ~ 35Ohms when connected, open the circuit without.  Additionally, make sure that switch S3 is down, by trial and error, I've found this causes impedance jumps.

  Hope this helps,

• LCR PXI-4072 floating or not floating device

  Hi all

  My question: 4072 LCR is a floating or not floating device (used for the measurement of the capacitance)?

  Thank you...

  The Hi and Lo led float in reference to the ground regardless of the configuration of the 4072.  Note that allowed on the 4072 maximum common mode voltage is 300VDC/CaRMS.

• 5900 diff amp clipping to 11V

  I tried to measure an IEPE sensor (Simulator) released in parallel to the amplifier signal conditioner. Looking for a scope, I got on with a nice 2Vpp sine 12V bias.

  If I place a PXI 5922 with a PXI-5900 differential preamplifier for 40Vpp inputrange.

  I need to measure in DC mode. The output of the 5900 is clipping in connection 11V.  (CH + to report, CH-shortcut to GND). I tried a 5900...  all the same

  Another point: the reading input range gives me 160V... Oops bug?

  OR-Scope 3.8.2 LV2011

  Another question: what is the output impedance of the 5900? 50 ohms?  It is not indicated in the specifications.

  Well, I think I found the solution for the clipping.

  And there's nothing wrong with the specification of the 5900, however, the definition of the commune of voltage range was missleading me.

  While the definition of "municipality" of the common voltage in a differential measurement is Vcm =(Vpos+Vneg)/2 "Common Voltage Range" is not the possible range of common blood, instead of the definition (by NEITHER?) I found here from the States:

  "The range of common mode voltage is defined as the oscillation of the admissible maximum voltage on each entry from the ground of the measuring system. Violating this constraint translates not only error measurement, but also of the possible damage to the components on the Board. »

  Something that should find its way into the specs of the understanding device and Specifications of Acquisition of data - a glossary

  So I can't measure a 12V GND signal with my 5900 input of the unit gain amp is probably capture one

  Leaving the input of 160V range calculated by NI_SCOPE... CAR?

• SMU-6363 pressure measurements

  Hi guys,.

  First post here. I tried to search first for documentation but empty is come.

  I use the analog inputs on the 6363 map to make some measurements of voltage. I have 2 questions:

  1. I know that the channels are limited to +/-10 volts for entries. I have a 25 Volt with a resistance line series regular (50mOhm) sense. I want to do a differential measure resistance across with 2 analog channels. The real tension between the two points will be in the range of mV, but the unique finished voltageon each will be ~ 25 V. Will this work?
  2. In a similar configuration, but on a 5 volt line can I build a differential measure through a resistance of sense current using 2 channels and then turn around and use one of these same channels for a single measure is complete wrt gnd?

  Thanks for your help!

  There is a row in the datasheet that States

  Maximum voltage of work for the analog inputs (signal + common mode)

  ±11 AI GND v

  So with a 25V common-mode voltage, you will hurt your card.  The 5V line should be fine.

  If you look at Digikey, there are chips specially designed to detect a current shunt.  The differential voltage amplifiers will become a simple nerve from the ground.

• Current inaccurate measurement using Shunt resistance

  Hello

  I try to measure the power of a pressure sensor 4-20 my using the PCI - 6251 DAQ and 249 Ohm shunt resistance.  The measurements taken by the DAQ card are slightly lower than expected.  Performed by a digital multimeter measures appear to be more accurate.  I tried the two configurations in the link provided below.  I read on the common-mode voltages and ground loops to try to fix this problem without success.  Any help would be appreciated.

  http://zone.NI.com/DevZone/CDA/tut/p/ID/7077

  
  

• 4204 (grounding issue) measuring device

  
  

  Hi Matthew,

  The PXI-4204 is a protection against overvoltages to manage up to +/-110 Volt transients.  It can measure between +/-100 volts.  My understanding of your configuration, the largest swing you could see with your configuration is 60 volts if differential measurement (if V1 were to 30 Volts and V2 to 30 Volts, say).  If your resolver of sync is more than 40 VDC above the ground data acquisition system, then the common-mode voltages can be a problem.  Otherwise, I don't think you should have a problem.  The DAQ hardware has a fairly high input impedance (2 MOhms differently) and should in no way damage the synchro resolver.

  Characteristics and the PXI-4204 product manual
  http://www.NI.com/PDF/manuals/373529c.PDF

  Let me know if you have other questions about this or if this response was not clear.

• Two signals interfering with each other

  Hello

  I have a problem with a trace of pressure and a vibration sensor. I have a card PCIe - 6341 DAQ. I connect my pressure signal to a channel (say ach0) and I connect the vibration to another analog channel (say ach7).

  In labview, I use an assistant DAQ. When I use it to sample only one of the signals, there is no problem. If I add two channels in the configuration dialog box, the signal pressure becomes superimposed vibration signal.

  Analog signals entering data show no interference (checked with an oscilloscope). I suspect that what is happening inside the data acquisition card.

  Any ideas why this happens?

  Thank you

  Masoud Mashkournia

  Hi Masoud,

  It seems that you see 'ghosts' on your channels.  The 6341 multiplex via the analog inputs.  Therefore, if you are scanning between high voltage and low voltage, especially when you use CSR, you can see ghost images if the signal from the previous channel file completely or have a path to the ground.  Here is a good article from the knowledge base that describes ways of eliminating this remanence.

  I noticed that you use the configuration of the CSR on your DAQ Configuration Wizard.  Try using a differential input configuration.  This can help eliminate unwanted common mode voltages.  In addition, you can try place a middle way in scanning which is connected to the ground at AIGND in the DAQ command scan.  This can help with the mass of the previous signal.  Most likely, you will want to scan in this order: pressure, ground, vibrations.

  Please let me know if it helps.

  Best,