PXI-6255 voltage limit

Hello,
I need your help for a signal acquisition : 12 inputs in 0-16V.
But the voltage limit for the most of the PXI cards is [-10V;10V]
I know that some cards like PXIe-4300 can measure more than 16V, but they less cost-effective.
Can make a differential mesure on a PXI-6255 to measure 0-16V ?
Thanks for your answer

The short answer is no. The reason is that each input, even in differential mode, can only handle a range of -10V to +10V relative to ground.
What I have done in these situations is use a voltage divider (2 resistors that will divide down the voltage) and then apply a scale in DAQmx to make the scale back to what you expect. Since you are dealing with a range of 0 to 16V, I would just use 2 100kOhm resistors to divide the voltage in 2. This would give an input range of 0 to 8V. Then setup a scale in DAQmx to multiply the read voltage by 2.
There are only two ways to tell somebody thanks: Kudos and Marked Solutions
Unofficial Forum Rules and Guidelines

Similar Messages

PXI 6255 shows -6.28 volt at all channels

Dear Sir,
I have a PXI 6255 modules. The module shows constant -6.28 volt at all channels for any analog input.What is the reason for it? Please reply as soon as possible.
Thanks.

Nothing connected? BIAS !
Read the documentation about voltage measurement and bias currents
Greetings from Germany
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'

Counter value jumps on occasion (PXI 6255)

I am using a PXI 8108 controller (Windows) with a PXI 6255 AI card. A pulse generator (1 KHz) is incrementing the hardware counter of that AI card in order to have an external reference clock, i. e. having a timestamp for each AI sample value.
I am reading 1000 AI values from several channels (together with 1000 counter values) via DAQmx blocks with a higher frequency than the external clock's 1 KHz (e.g. AI Rate 5 KHz-> reading every counter value approx. 5 times). Every now an then I am losing counter values, e. g. counter value 6789 is followed by 6823.
Shouldn't be the PXI card's counter buffer independant of Window's CPU load? Getting 1000 values from the card buffer, the jumps are even located in the middle of the 1000 values. Maybe there's a problem with atomicity while reading from the buffer, so that I get 500 values from the buffer, (pause), and 500 more values from a later point in time. Is this possible?
I am sure, I can not blame the digital pulse generator (from Hameg Instruments) for dropping pulses.
Attachments:
counter-daq.png ‏20 KB

Hello,
If the first scan only places 4 samples in the AI FIFO (2 less than the number of channels requested), then I would expect this loop to run forever in aiex1.cpp (I added some debugging prints to make it easier to see the channels that should be getting returned).
       while ( m < numberOfChannels )
        if(!board->AI_Status_1.readAI_FIFO_Empty_St())
            value = board->AI_FIFO_Data.readRegister ();
            aiPolynomialScaler (&value, &scaled, &scale);
            printf ("Channel %d: %e,\n", m, scaled);
            m++;
    printf("\tEnd of Sample %d\n", n);
How is the example able to proceed past this loop?
I have checked the code for FIFO flushes and resets between aiStartOnDemand (board); and when the FIFO gets read. I have also run the example with 6 channels, this time on Windows.
To proceed we would need these items:
1) We would need the exact output (with my added debug prints).
2) A complete dump of all registers accessed during the example.
Steven T.

PXI-6255 Channel Configuration

The documentation for the PXI-6255 is VERY unclear (to me) on configuration. I found the attached sample VI and modified it to test my new card. The VI runs to make the relay connections (without the ~), but when I add the "~" to disconect, the attached error results. The error refers to "channels" and I can find NO documentation on how to set up "channels" for this card. The documentation seems to freely switch syntac between channels and com1 for example? What am I missing.
Attachments:
Switch Connect-Mult Channel working.vi ‏26 KB
PXI-2566 error.jpg ‏19 KB

Hi Alyeska,
When you say that you modified the example so as to test your new card, I am unclear as to what you are trying to do. What functionality do you want to test? The example that you attached configures the device, makes all the connections on the scan list, waits for those connections to settle, and then disconnects all the connections listed on the scan list returning to the original position, and waits for that to settle.
Now to address your confusion about “channels” and “com”s. Your PXI-2566 switch module is “Single Pull Double Throw (SPDT).” This can be seen in the attached image from the excellent NI-SWITCH Help that installs on your computer with the drivers. While most switch modules have a large number of input channels that can be connected one at a time to one outgoing common or “com” pin, your module has 16 common outputs, each of which has only two inputs. The two input channels are labeled “NC” for normally closed (connected) and “NO” for normally open.
The cause of your error message could be two things. The message states that it does not understand the “~” symbol, since it looks for a channel name (for example: ch0 or com0 or nc0) following the specified device. In order to disconnect, the “~” has to come before the device name, so your scan list would look like “~/RelayDevice/no0->com0.”
However, even when the “~” is in the correct location, you still may have difficulties. This is because DAQmx’s Scan mode is by default “Break Before Make” which means that the hardware will break one connection before making another. The only time the “~” disconnect needs to be used is when “No Action” mode is engaged and connections are not broken unless explicitly told to do so. This example program first connects the channels on the scan list, so when it begins to run through the list and sees the “~” it will throw an error. If you look at the block diagram, the disconnect function follows the connect, so every connection that was made on the scan list is then disconnected for you and the relays will return to their default NC position.
I am unsure of how you want to test your new card, but there are a number of great example programs included in LabVIEW with the switch driver. These can be found by navigating to the Help Menu>> Find Examples>> expanding the Hardware Input and Output folder>>expanding the Modular Instruments folder>> and then looking in the NI-SWITCH file. When you click on an example VI, a brief description will appear in the Information box to the right of the Example Finder. You might want to look at Controlling an Individual Relay.vi, Making Connections on a Switch.vi, and Software Scanning.vi. The other examples are for using switch modules with Digital Multimeters and Thermocouples.
Also, when you find some documentation unclear, I find the NI-SWITCH Help to be very useful. It can be found by going Start>> Programs>> National Instruments>> NI-SWITCH>> Documentation>> NI Switches Help. Here you can see the pinouts for your specific device and find explanations of syntax, scanning, and triggering.
I hope this explanation helps, Mallori M.
Message Edited by mallorim on 01-16-2008 07:28 PM
Mallori M
National Instruments
Global Customer Education Program Mananger
Calculate the time you will save with NI Training
Attachments:
single pull double throw.PNG ‏4 KB

780 SLI - "Voltage Limit" and "Utilization Limit" Flags

Hello,
I'm trying to pinpoint an issue I'm having with my video cards, and wanted additional advice before I make purchases. My questions will be: is there anything else I should try? Is there anything I can do to pinpoint the problem?
My setup:
Core i7-950 - OC'd to 3.84 ghz
ASUS P6X58D-E - mobo
2x MSI n780 TF in SLI
Corsair 850AX Power Supply
Also drawing power: 5x Hard Drives; Typically only 2 are running at one time (OS RAID), the other 2 are a backup RAID I only use to archive stuff, and the last is a Linux drive that Windows doesn't even see
Issue:
Most games run without issue; but Metro Last Light is unstable. I run at 1920x1080, Advanced Physx, 2x AA, Very High quality and Very High Tessalation. There are times when I get 60 FPS (V-Sync); however, there are times that the performance drops to 6 or 14 FPS. When it is at 14 FPS it is still playable, but 6 FPS is terrible. I use Afterburner's OSD to monitor GPU Usage, Temp, and FPS. When it is at 6 FPS, it is only using 12% of either GPU at most.
While investigating, I noticed a few things in Afterburner that stand out when this occurs.
1) The Core Clock drops down (throttling?)
2) The "Voltage Limit" and "Utilization Limit" flags are both set on both GPUs.
My thoughts:
I'm thinking that my Power Supply isn't quite big enough. I thought this may become an issue when I first bought the two cards (I was previously running 2 460's on SLI, then upgraded to 780s).
My question is if the video cards are pulling the power supply's limit - will this trip the two flags? I would have thought the Voltage Limit would indicate the voltage going too high; but power supply being strained should drop voltage.
I have not changed any of the voltage settings to the card - they are whatever MSI has them set to for the stock OC.
If I buy another PSU, I don't like to go cheap - so it will definitely be beefy. Before I drop a few hundred on it, I want to be sure the Power Supply is the issue. Is there anything else you guys/gals can think of that may be an issue? Any tests I can do to confirm?
The new Thief seems to run fine; also Kombustor runs without issue (but only runs on one GPU - does not SLI). I have no other stability issues - the PC doesn't randomly shut down or reboot. It just seems to be Metro Last Light - but Metro is also the most demanding game that I own.
Any assistance or feedback will be greatly appreciated!
Edit - Update:
I tried disabling SLI to see if the issue would improve by only loading 1 GPU. No difference at all - no better or worse. Same flag (just only on the one GPU), same exact FPS 6.4.
I installed GPU-Z to be able to monitor core voltage. It normally runs at about 1.1 volts. However, once the issue occurs it is as low as 0.875 volts. Seems to confirm the PSU may be an issue. Any feedback or additional confirmation is still greatly appreciated!

Apologize for the bump - I could not see a way to edit the original post. However, I wanted to make sure this information is available in case others had similar issues.
I found an even better solution. NVIDIA has an updated "Physx" driver - you have to download it from the NVIDIA site (i.e. Other NVIDIA drivers, not GeForce). Look for Physx version 9.13.1220 or later. 9.13.1220 was release on 1/27/2014 - but an older version is included in the most recent GeForce drivers for some reason.
The patch notes from Physx 9.13.1220 specifically state:
*Changes & fixed issues in this release
**Fixes a bug that caused the Metro Last Light to not be GPU accelerated on some systems.
With this software update I can enable Advanced Physx and max settings in Last Light and still run at 60 FPS.

Output current and voltage limit

I am currently using a PXI 4130 to output 1mA with 2V backing. I am measuring the voltage and current with a DMM and I am getting good values. I need to be able to prove that the voltage and current will not largely exceed 1mA or 2V so that it will not damage any components. Looking at the code I used it says that voltage level range is 6 and current limit range is 20 and I am not sure what that means exactly. What precautions/values can I change to make sure these values never get exceeded
Thanks
Attachments:
NI-DCPower Source DC Voltage.vi ‏48 KB

Hello lvuser,
In you code you are also measuring the voltage and current back into your program. You can make programmatic decisions based on these measurements, for example, stopping the program based off of a voltage that floats too high. Our devices make sure to try to maintain the voltages and currents you tell them by completing a closed loop system with measurements taken on the same inputs that are sourcing. Try taking the readings you get in your program and using some threshold to trigger a case statement that holds a function to close the resource and turn off the generation.
Regards,
-Travis E
National Instruments
Applications Engineer

PXI-4110 current limit

I am programming a PXI-4110 with LabWindows. I am trying out the current limiting. I have an output set to 5V with a 1K load resistor; this makes the current 5mA. I set the current limit to 2mA to see it work. When I read the voltage and current it is still 5V and 5mA. Here is my code:
g_voltageLevel_ch0 = 5.0;
g_currenLimit_ch0= 2.0e-3;
status = niDCPower_ConfigureOutputFunction(vi_4110_0, channel0Name, NIDCPOWER_VAL_DC_VOLTAGE);
niDCPower_error_message(vi_4110_0, status, errorMessage);
status = niDCPower_ConfigureSense(vi_4110_0, channel0Name, NIDCPOWER_VAL_LOCAL);
niDCPower_error_message(vi_4110_0, status, errorMessage);
status = niDCPower_ConfigureVoltageLevel(vi_4110_0, channel0Name, g_voltageLevel_ch0);
niDCPower_error_message(vi_4110_0, status, errorMessage);
status = niDCPower_ConfigureCurrentLimit(vi_4110_0, channel0Name, NIDCPOWER_VAL_CURRENT_REGULATE, g_currenLimit_ch0);
niDCPower_error_message(vi_4110_0, status, errorMessage);
Solved!
Go to Solution.

I'm getting an error now. I have a 1K resistor on each of the outputs so I will see some current.
Look for these lines
to see comments I am sending you about the code.
When I start my program I call a function PXI4110_HardwareInit() to get things set up. This part seems to look OK.
/************************************** PXI-4110 ****************************************/
// PXI-4110 hardware definitions for initialization
static ViSession vi_4110_0 = VI_NULL, vi_4110_1 = VI_NULL, vi_4110_2 = VI_NULL;
/* The channel names are length 2 because the maximum size of the strings
from the each textbox on the UI is 1. */
static ViChar channel0Name[2] = "0"; // 0V to 6V channel
static ViChar channel1Name[2] = "1"; // 0V to 20V channel
static ViChar channel2Name[2] = "2"; // 0V to -20V channel
// inputs
ViReal64 g_voltageLevel_ch0 = 5.0;
ViReal64 g_voltageLevel_ch1 = +13.0;
ViReal64 g_voltageLevel_ch2 = -13.0;
ViReal64 g_currenLimit_ch0 = 500.0e-3;
ViReal64 g_currenLimit_ch1 = 500.0e-3;
ViReal64 g_currenLimit_ch2 = 500.0e-3;
void PXI4110_HardwareInit(void)
ViStatus status;
ViChar errorMessage[256];
   ViChar resourceDCSupplyName[256] = "PXI-4110";
// set channel 0 to +5.0V
status = niDCPower_InitializeWithChannels(resourceDCSupplyName,channel0Name,VI_TRUE,VI_NULL,&vi_4110_0);
if(status < 0)
  niDCPower_error_message(vi_4110_0, status, errorMessage);
status = niDCPower_ConfigureOutputFunction(vi_4110_0, channel0Name, NIDCPOWER_VAL_DC_VOLTAGE);
niDCPower_error_message(vi_4110_0, status, errorMessage);
status = niDCPower_ConfigureSense(vi_4110_0, channel0Name, NIDCPOWER_VAL_LOCAL);
niDCPower_error_message(vi_4110_0, status, errorMessage);
status = niDCPower_ConfigureCurrentLimitRange(vi_4110_0,channel0Name, 1.0);
niDCPower_error_message(vi_4110_0, status, errorMessage);
Set_PXI_4110_Outputs();
status = niDCPower_ConfigureOutputEnabled(vi_4110_0, channel0Name, VI_FALSE);
status = niDCPower_Initiate(vi_4110_0);
niDCPower_error_message(vi_4110_0, status, errorMessage);
static void Set_PXI_4110_Outputs(void)
ViStatus status;
ViChar errorMessage[256];
// channel 0
status = niDCPower_ConfigureVoltageLevel(vi_4110_0, channel0Name, g_voltageLevel_ch0);
niDCPower_error_message(vi_4110_0, status, errorMessage);
status = niDCPower_ConfigureCurrentLimit(vi_4110_0, channel0Name, NIDCPOWER_VAL_CURRENT_REGULATE, g_currenLimit_ch0);
niDCPower_error_message(vi_4110_0, status, errorMessage);
Then I send a message on ethernet to enable the outputs: When I enable the outputs this function reads the voltage and current outputs and sends this information to a application on my host computer. This information corresponds to what I set it to and what I see with a volt meter.
void PXI_4110_enable_outputs(void)
ViStatus status;
   ViReal64 measuredVoltage, measuredCurrent;
   ViBoolean inCompliance;
ViChar errorMessage[256];
// set the outputs
// Set_PXI_4110_Outputs();
status = niDCPower_ConfigureOutputEnabled(vi_4110_0, channel0Name, VI_TRUE);
      /* Wait for the outputs to settle. */
     Delay(50e-3);
// check channel 0
status = niDCPower_MeasureMultiple(vi_4110_0, channel0Name, &measuredVoltage, &measuredCurrent);
niDCPower_error_message(vi_4110_0, status, errorMessage);
niDCPower_QueryInCompliance(vi_4110_0, channel0Name, &inCompliance);
niDCPower_error_message(vi_4110_0, status, errorMessage);
Now I send a message to change the current limit. This is where I have trouble. I try and limit the current on Channel 0 to 2mA. Since the output voltage is 5Volt and the resistor is 1K the current will exceed the current limit which is what I am trying to test. I get an error in this function>
   g_currenLimit_ch0 = CommandData->data;
   status = niDCPower_ConfigureCurrentLimit(vi_4110_0, channel0Name, NIDCPOWER_VAL_CURRENT_REGULATE, g_currenLimit_ch0);
   niDCPower_error_message(vi_4110_0, status, errorMessage);
I see g_currentLimit_ch0 = 2e-3 whic is whatI sent. but my status is a negative number. The message is "Invalid value for parameter or property"
vi_4110_0 is the handle I got earlier.
channel0Name ="0"
and g_currentLimit_ch0 = 2e-3
I do not understand why I am seeing and error here?????????????????????
thanks in advance for your help,
Don

PXI-6255 not identified in MAX as DAQmx

We recently purchased a PXI-8108 controller for use as a spare and I'm having difficulty getting it to play well with our existing hardware and software. The controller we have been using is an older PXI-8106.
The new controller has Windows 7 where the old had XP, so I had to use more recent versions of PXI Platform Services and MAX, as well as DAQmx. The versions I've installed are: PXI Platform Services 3.0.4, MAX 5.3.1, DAQmx 9.2.2. I can't use more recent version of DAQmx because our we are using LabVIEW 8.5.1 and anything more recent doesn't support that.
The 6255 is showing up in the device manager under Windows, and the properties show that it is using the same hardware driver (nixsrkw.sys, rev. 1.13.0f4) as we use on the old controller. The 6255 also shows up in MAX, with a device identifier of PXI13::15:INSTR, but not listed as a DAQmx device. So, when I import the MAX settings file, the defined tasks won't run.
I haven't found any postings in the forum that quite match this scenario. Anyone have any ideas?
Thanks,
Mike

Mike,
Firstly, I want to let you know that you will have problems using LabVIEW 8.5 with Windows 7. The oldest version of LabVIEW supported in Win 7 is LabVIEW 2009 SP1:
http://digital.ni.com/public.nsf/allkb/B972242574D4BB99862575A7007520CB
About seeing your device in MAX, can you post a screenshot of what it looks like?
Jon F.
Applications Engineer
National Instruments

PXI 6030e Voltage measurement

Hello All,
I have a PXI 6030E DAQ with a SCB-68 connector board. I am setting up a simple voltage divider and connecting my Vout to pin 68 on the SCB-68. My ground is going to pin 67. My Vin is 5 V DC. I used DAQ assistant to automatically generate code to read the voltage and put it in a while loop. My R1 is a device (Copper Interdigitated Electrodes coated with Dow Corning Silicone), and my R2 is 100 Mohm resistor. I am using an OP Amp as an isolator between the impedance on my DAQ and my voltage divider. Unfortunately, when I run this program it will not reach a steady value or progrssively drop the voltage. Is there something I am missing here as to why it will not allow me to get the reading I want?

Thank you! I actually found it last night 5 minutes after I wrote the message. I constructed the Wheatstone bridge and used a differential reading from the 2 nodes connecting each leg. Unfortunately I received a reading that is about 10 % higher than what I calculated. When I do a reading with respect to ground (RSE) and probe both sides of the bridge separately (with a single channel, not simultaneaously) I simply subtract the reading I receive from each side and obtain the correct value. Ideally when using the differential method in DAQ Assistant it is suppose to give me the right reading, but why is this giving me a different value when DAQ assistant is configured to take a differential reading. My program is exactly like the example provided by NI. Except I am adding the values from each signal and outputing them to a numeric indicator vi. All suggestions are welcomed!
Thank you.

PXI-5404 Voltage Output

I want to use the PXI-5404 to generate a frequency sweep and am executing the example found here: http://zone.ni.com/devzone/cda/epd/p/id/3820
Frequency sweeping works well for the SINE output, but the voltage levels are much lower than expected. The SINE output for CH 0 is at a maximum ±30 mV, and the CLKOUT output for CH 0 is a DC signal at whichever high voltage I specify.
Please help.
Thanks,
Robert

Hi Robert,
I have tested the PXI-5404 and PXI-5105 on our test chassis and see that the output works properly. For this test, I had connected the CH 0 SINE output to CH 0 of the PXI-5105 and CH 0 CLOCK Out to CH 1 of the PXI-5105. CH 0 impedance was set to 50 Ohms and CH 1 to 1 MOhm.
So it appears that there is either an issue with your SMB connection or the PXI-5404 card itself. You mentioned that you tried a different scope and saw the same results so I assume that the problem is not with the PXI-5105. If you try another cable and ensure a proper connection, but still see the same results you more than likely have a broken PXI-5404. In this case you can create an RMA request by calling 1-866-ASK-MYNI (1-866-275-6964).
Brian G.
Brian G.

UMI 7772 voltage limit?

Hi,
does anybody know if the UMI 7772 releases voltage under 5V?
I tried to run a stepper motor wit the UMI 7772 (with MAX). There is no error at MAX, Axis is moving, no LEDs are red, but the motor isn't moving?! So my only idea is that the voltage released from the UMI Axis is beneath 5V (because the motor needs 5V at least). I connected the motor to the step signal and digital ground of the control connector of the UMI Axis. Are there other possibilities? Can I set the voltage release to 5V anywhere?
Thanks a lot.
Steffi Kono

I just checked the manual briefly, and it is stated that also in the 5V input version optocouplers are used.
Optocouplers usually need several milli-amps to drive the input LED. Some work with 3mA, some need 5mA, virtually all will work with 10mA input current.
The TTL output of the UMI/NI board will be current limited by the 3.3kOhm pull-up resistor. With the load of an optocoupler, the output voltage will break down to the forward voltage of the input LED which probably is around 1.0V at the given current limit.
To drive optocouplers, it is better to use the outputs of the NI boards/UMI in "sink mode". Connect a +5V source to the (+) terminal of the driver input in question, and connect the (-) terminal to the output of the NI board. The power supply must have common GND (DGND) with the NI board. In sink mode, the outputs can drive up to 24mA which is more than sufficient for all optocoupler inputs.
Note that the logic level of the outputs is reversed. You should set them to "active low" mode. I.e., if you write a 0 into a given output, the output transistor will switch on. In source mode, the voltage across the output resistor would break down, thus yielding a TTL low level. In sink mode, current will flow from the +5V source through the optocoupler and activate it. This is not very important for the STEP output, but for the DIR output this is VERY important - direction of movement will be reversed if you use sink mode instead of source (TTL output) mode.

PXI-4496 voltage range

Can I increase the voltage range of individual channels on the PXI-4496? I'm guessing not, but I'm hesitatiting applying large attenuations to my signal (a factor of 4 is likely) with the fear of losing significant accuracy.
Currently I have single IEPE sensors going to individual channels, but I'm looking to sum several IEPE signals. This means that the incoming voltage will be multiplied (by the number of summed channels), so I'll need more than +/- 10V or will need to attenuate the signal.
Thanks

ap8888,
Unfortunately, the input range for this device is +/- 10V, and that cannot be increased. Rather than summing the channels prior to input, have you considered summing them (or performing other operations as needed) in software AFTER it has been inputted? This way, you wouldn't have to worry about attenuating the signal prior to input of the 4496.
Katie
Katie Collette
National Instruments

Re: Screen Freeze and Voltage Limit Issue

yes

Voltage Limit is still an issue.Whenever i check with afterburner i see it reaches it's max during games and that's probably throttling gpu,causing stuttering.
Can't save vbios to check if it's up to date because whenever i use nvflash it completely lo...

CFP-TC120 Inter-channel voltage limit

Hi,
I am using the TC120 thermocouple modules to record temeratures from a number of test machines. Originally we used sheathed thermocouples but we now wish to use unsheathed thermocouples bonded to the specimens.
The module specification states no channel-to-channel isolation but that the inputs are differential. My question is what voltage can the TC120 tolerate between channels, both in terms of degrading the accuracy and possible damage to the module?
It would be too costly to provide a TC120 module for every test machine as each machine uses only 3 thermocouples but we have 50 machines. The thermocouples are essentially at ground but there may be several volts between the machines.
Thanks
Tony

Dear Tony,
Typically you cannot use two channels at different potentials on the same FieldPoint I/O module. As you know, cFP-TC-120 do not offer channel to channel
isolation, and they measure signals with a reference to the Common of
the terminal base (as defined by the Com terminals). Thus, a signal
that is at a potential of 100 V with reference to the isolated
backplane could be measured against other signals that are at the same
potential -- the circuitry will handle small potential differences
(less than 4 V), but not against signals that are at 150 V with
reference to the backplane. If you wish to measure two signals that are
at different potentials, then you will need multiple modules. (KB)
You will get erratic readings when stray currents run through the
module. If two or more
of the thermocouples are connected to different potentials, current runs from the thermocouple into the module and out to
the other thermocouple. Depending on the range used, if more than 0.5
to 2.0 V is run through the thermocouples, one or more of the readings
can become erratic. If these voltages are more than 0.5
to 2.0 V and another thermocouple is grounded, has a common-mode
voltage, or is connected to a voltage source, erratic readings will
also occur. (KB)
Hope you will find these links helpful: Improve Accuracy, Considerations for Analog Signals.
Regards,
CLA | LabVIEW 7.1... 2013
www.renishaw.com

PXIe-6363 Voltage Measurements

Hi Guys,
First post here. I tried to search the documentation first but came up empty.
I'm using the analog inputs on the 6363 card to make some voltage measurements. I have 2 questions:
I know the channels are limited to +/- 10 volts for the inputs. I have a 25 volt line with a series current sense resistor (50mOhm). I want to make a differential measurement across the resistor using 2 of the analog channels. The actual voltage across the two points will be in the mV range but the single ended voltageon each will be ~25 V. Will this work?
In a similar setup but on a 5 volt line can I make a differential measurement across a current sense resistor using 2 of the channels and then turn around and use one of those same channels to make a single ended measurement wrt gnd?
Thanks for your help!
Solved!
Go to Solution.

There is a line in the data sheet that states
Maximum working voltage for analog inputs (signal + common mode)
±11 V of AI GND
So with a common mode voltage of 25V, you will hurt your card. The 5V line should be fine.
If you look at Digikey, there are chips specifically made to sense a current shunt. The amplifiers will turn the differential voltage into a single ended relative to ground.
There are only two ways to tell somebody thanks: Kudos and Marked Solutions
Unofficial Forum Rules and Guidelines

PXI-6255 voltage limit

Similar Messages

Maybe you are looking for