Aquisition of a voltage Signal with PXI 6713

Hi.
I want to make voltage aquisition with a PXI 6713 card. I take the Channels ai16 to ai33. The voltage at the clamp is 3.886VDC ( measured with a DMM ). When i measure the voltage and calculate it into a current ( see my applikation atteched ) the result is something between -10 and -24mA?!?!?
Are the settinges in the DAQmx Express-VI "analog voltage aquire" wrong or could it be another Problem?
My settings are:
RSE
voltage measuring from 0 to +8VDC
N Samples
I hope of yous Answer.
Thanks
Attachments:
analog_voltage_aquisition.jpg ‏33 KB

Is it a trick question??
First of all, Looks like you mentioned the card wrong PXI 6713 is an AO card, without any AI channels
Which card are you using??
Are you connecting a 390 ohm Resistance on your connector block to convert current signal to Voltage equivalent?? ( Sounds like you are not )
Are you measuring the Voltage correctly in the first place??
if you are not, check if the signal is connected correctly for RSE mode
Hope this Helps
Regards
Dev
Message Edited by devchander on 07-28-2006 07:35 AM

Similar Messages

Timebase synchronization issue with PXI 6713

As indicated in another post, I need to use a common timebase to all cards within my PXI chassis to synchronize my acquisition/generation DAQmx tasks.
I performed that successfully by setting timebases of all boards from the 20MHz timebase of a E-series DAQ board.
I have another system setup where I do not have E-series DAQ boards but only M-series. In this case, I tried to synchronize all the cards with the 10MhzRefClock of a PXI 6254 board. It seemed to work correctly, until I looked at the analog output signal of one PXI 6713 board.
This device has 8 analog outputs, I performed as for DAQ boards : I set its timebase to a 10Mhz clock. When I have at least two outputs with hardware timing I observe on scope really weird signal : nothing is visible when all outputs are left to zero volt, but when another voltage is set, the output toggles at very high frequency between 0V and the setting voltage. When two outputs are set to values different from zero, the output also toggles but between these two settings...
I thought it was a board failure, but I checked with another PXI 6713 and the behavior is the same.
When synchronizing with a 20MHz timebase, everything is fine, but 10MHz clearly shows this issue. I checked the 6713 documentation, and it seems possible to use a timebase different than 20MHz.
I attached a VI that illustrates the problem : I create a DAQmx task containing 2 AOs, where 10MHz timebase is taken from a M-series DAQ board. A hardware timed single point timing is configured and outputs are updated in a while loop. If you connect a scope to the first analog output, you will see the phenomenon.
Everyting is fine when you select a 20MHz clock as a timebase. 10MHz leads to this issue. I also tried to synchronize through PXI backplane clock (i.e. /6259_1/PXI_Clk10) but it leads to the same problem.
Please note that using the same 10MHz synchronization on DAQ cards (PXI 6040E, 6071E, 6254, 6259...) for AO works perfectly. I only encountered this problem with PXI 6713 board.
Message Edité par Inpriser le 08-18-2006 02:54 AM
Attachments:
Synchro 10 MHz PXI AO.vi ‏34 KB

Inpriser,
You wanted to use the PXI 10MHz clock to synchronize to 6713s using the PXI capabilities. I’m afraid that since the AO series doesn't have a PLL, you won't be able to use the PXI 10 clock.
I made a few search and found this:
“Neither the 6713 nor any of the AO series support PLL synchronization. However, the M-Series does, though in that case you are limited to a smaller number of analog outputs. Regardless, the best option is using an Arb or other card that can use the Star Trigger, or an m-series device with PLL synchronization capabilities.”
For more info’s about how to deal with PXI and PLL, please check this forum:
http://forums.ni.com/ni/board/message?board.id=170&message.id=11986&requireLogin=False
I’m sorry to disappoint you, hoping you’ll manage to deal with that,
Regards,
BRAUD Jean-Philippe
Field Sales Engineer - Nord et Centre France
LabVIEW Certified Developper

How to measure different signals with PXI-2501

Hello everybody,
i have a an understanding problem.
I have a PXI-2501 switch and i want to measuere signals with the pxi-4071, so far so good.
I did some voltage- measurements and everything worked fine. Then i disconnected the power source and measured the temperature with a PT1000 in four-wire-mode ... also worked fine.
But i want to measure voltage and temperature, in the same VI, so i connected the voltage signal on CH0 and the PT1000 at CH5 (in four wire mode), and now i get problems. The temperature is fluctating. There are a few measurements that seems OK, and then i see some that are far away from the truth.
The VI consists of a state machine, the measurements are done in different states, of course with the correct scan list for each measurement.
Any suggestions? Am I doing something completely wrong?
Thanks
(and excuse for my english )

Hi Roman,
id I understand you right:
The temperature measurement works fine, if the sensor is directly connected to the 4071, but if connected via the 2501 you see the big deviations?
Have you measured the the resistance of the Switch-Matrix yet?
kind regards
Heinz

How to continously generate a voltage signal with dynamic amplitude.

Hello all,
I am looking for ideas and pointers (help in other words). I would like to generate a voltage signal (sine for example) on a AO of my NI cRIO-9263 (DAQmx). The signal should be:
continuous (without jumps ie. smooth)
dynamically able to be change the amplitude, frequency and sampling rate.
interuptable so that the AO can be turned off.
I have tried to use the DAQ Assistant but once it runs in continous mode, I have the impression that the waveform should not be changed. Is there maybe a way where I send repeatedly N samples of the waveform to the AO and gain more control over the signal that way. But if I do that how can I ensure that the signal is continous?
Further more this output has to be generated in an event application ie. in the background.
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See if this example VI helps
Ches this one too

Generate PXI Trigger Signals with PXI-6115

Hello,
I have a question.
I have a PXI-6115 and some other card in my mainframe.
These other cards nee 10 Mhz pulses on line PXI-Star1 and 2.5 MHz on PXI_trg7.
So I thought to apply (somewhere on my PXI 6115 card) 10 MHz, divide the 10 MHz with a counter to 4 and route all this things to the backplane.
But I don't understand how to do this.
There are no good examples.
And as far as I know the PXI-6115 isn't yet supported by DAQ-MX.
Can anybody give me some good advises or tips, white paper or so to make me solve my problem ???
Thanks Ruediger

I don't have time to write any example snippets right now, but I'll try to provide you the general idea and hopefully you can take it from there.
First, it's not clear whether you want to generate the 10 MHz from the 6115 and send it to other devices in the system or accept the 10 MHz externally and route it to the rest of the system. If you're bringing in the signal externally, I would simply using the DAQmx Connect Terminals VI to route the signal from a PFI line on the front connector of the board to one of the PXI trigger bus lines in the backplane. Check out the routing table in MAX to see what routes are possible. To perform this route, the driver will have to route through Counter 0 so you won't be able to use Counter 0 for anything else.
If you want to generate 10 MHz from the 6115, I would create a continuous pulse train task on Counter 0 using the CO Pulse Ticks version of the Create Channel VI with a value of 2 for both the high ticks and low ticks input. However, to achieve 10 MHz clock on a PXI trigger line, you'll have to perform a couple of modifications that typically aren't done with counter tasks. First, you'll need to use the DAQmx Export Signal Property Node to route the Counter Output Event to the desired PXI trigger line. You can find this property by navigating the following menu hierarchy Events->Counter Output Event->Output Terminal. By default, the driver routes this event to the Ctr0Output pin on the front connector of the board. Using this property will override this behavior and route the output of the counter to a PXI trigger line instead. Second, you will need to change the output behavior of the Counter Output Event from toggle to pulse. This can be through the Events->Counter Output Event->Output Behavior property. Normally, when generating pulse trains, the high ticks and low ticks parameters from the Create Channel VI determine the frequency and duty cycle of the pulse train. When the high ticks count expires, the output of the counter toggles. The low ticks value is then loaded into the counter, and the counter output toggles again when the low ticks value expires. This process repeats to produce a pulse train of the desired frequency and duty cycle. Since the counter uses a 20 MHz timebase and has a minimum low ticks and high ticks value of 2, you can only produce at maximum a 5 MHz pulse train using the toggle behavior. However, by changing the output behavior from toggle to pulse, the counter output will issue a short pulse each time the high ticks and low ticks counts expire yielding a 10 MHz clock signal.
Now that you have the 10 MHz signal taken care of, you need to generate a 2.5 MHz signal from it. My guess is that since you have a 6115, you already have plans for the AI engine so I'll describe a route that uses AO instead. First, create an AO task to perform continous waveform generation. Use the DAQmx Channel Property Node and set the Use Only Onboard Memory property to true. Setting this to true will cause the driver to download the waveform once upon starting the task and replay the waveform from the onboard FIFO. Since you're only using this task to generate a clock, you don't really care about the data and this will prevent unneccessary traffic across the PCI bus. Next, use the DAQmx Timing Property Node to set the Sample Clock->Timebase->Source to the PXI Trigger line that you're generating the 10 MHz clock on, and set the Sample Clock->Timebase Divisor to 4 (10 MHz / 4 should give you a 2.5 MHz sample clock). Last, use the DAQmx Export Signal Property Node to set the Clocks->Sample Clock->Output Terminal to the PXI Trigger Line you want to generate the 2.5 MHz signal on.
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Can I measure small AC voltage signals with a FP-Ai-100

I would like to measure a 0-5VAC signal in a cFP-AI-100 module,
does anyone know if this is possible?
Thanks
Dusty

According to the specification sheet you should not really see a problem although one other major influencing factor is the 'loop' rate or in other words what else you have going on at the same time.
The maximum sampling rate was quoted at 360Hz but it will also depend on what filters are selected as well.
What frequency is the signal ?
The data sheet can be found here
http://www.ni.com/pdf/products/us/cpf_fp_ai.pdf

How Do I Configure the PFI Lines as input in PXI 6713 module

Hi,
I have PXI 6713 module in my PXI 1044 chassis. I have configured PXI 6713 module to geneate certain analogue signals to my board.
Board inturn process this analogue signal and responds back the status signals through a status register on the board. In my application,the status bits in status register of the board are mapped to the PFI 0:3 bits on PXI 6713 module ( pins 11,10 , 42 and 43).
My query is how do i configue the PFI lines as input in PXI 6713 module to read these status bits ??
May be below explanation could give you little bit more information w.r.to my query.
When i use NI USB - 6008 module to read the same bits , since this device has 12 digital I/O lines, i could able to read the status bits in to the last 4 digital lines by configuring the those digital lines as input.
In PXI 6713 module i have only 8 digital lines. These 8 digital lines i have used to send the digital signals to the board. I am left with no digital I/O lines. Hence i couldn't use these digital lines. I am left with only one option to use. Theya re PFI lines. Moreover the status bits in the pin out of board are mapped such that the bits can be read through the PFI lines.
I am wondering do we have any example code to use inorder to read these status bits on the board using the PFI lines.
Please let me know if you need additional information to help me out.
Thanks.
Solved!
Go to Solution.

Hello There,
When using the PFI pin as an input, you can individually configure each PFI for edge or level detection and for polarity selection. This PFI information can be referenced in the DAQ Analog Output Series Manual on page 6-1 (http://www.ni.com/pdf/manuals/370735e.pdf). Unfortunately, the PXI-6713 PFI lines are only capable of timing input and output signal for AI, AO, or counter/timer functions. The option of creating static DI from the PFI lines is not available for the PXI-6713. However, some cards have this capability. Newer National Instruments products with PFI lines have the option of setting PFI lines as:
Static Digital Input
Static Digital Output
Timing Input Signal for AI, AO, DI, DO, or counter/timer functions
Timing Output Signal from AI, AO, DI, DO, or counter/timer functions
(http://digital.ni.com/public.nsf/allkb/14F20D79C649F8CD86256FBE005C2BC4)
When set as static DIO, the PFI lines are assigned to a different port (eg. PFI0-7 is Port1). More details about this can be referenced at:
http://digital.ni.com/public.nsf/allkb/DA2D3CD0B8E8EE2A8625752F007596E1
http://digital.ni.com/public.nsf/allkb/862567530005F09E8625677800577C27
Regards,
Roman Sandoval | National Instruments | RF Systems Engineer

I can't reset my PXI-6713.

I can't reset my PXI-6713. My os is Windows 2000 , LV 6.1 , Nidaq 6.8.0 . I have another card in the pxi chassis , a 6704 wich I can reset. Im using the Reset vi located in Daq AO . I know I have the right dev number as I can set the analog outputs to any level I choose.

Reset on the PXI6713. I found out the 6713 analog outputs won't respond to the Device Reset.VI because of the way the hardware is designed. I don't get an error code except 0 (ok )on the status output. I know the reset failed because I set the outputs to a voltage and they did not go to Zero. I also have a simulator analog card PXI6704 which would respond to the Reset.
Now I just send zero volts to the outputs and that solves the problem. I think doing a low level the STC Joint_reset_register (72) I could reset the 6713
thanks for all.
P.S I tried this with the CVI Init_ , it did not work either.
John

Is there an output switch at the analog front end of PXI-6723 and PXI-6713?

I was reading the analaog output user manual and i could not find this. Is there any output switch just before the analog output of each channel for PXI-6723 and PXI-6713? I am would like to have total isolation between when these output are not needed. If yes, is there any specification to refer to?
Thanks.

Hello Chris,
I would recommend having a look at the examples in the LabVIEW
example finder to start with. In particular i would look at 'Cont Gen
Wfm-Ext Clk.vi' This is a basic example that allows you to output a
waveform through the card and source an external clock source to do
this. I would recommend exporting the sample clock that you wish to use
from the 4462 on one of the RTSI lines and then setting this as the
sample clock source for the Analog output card.
Another good example to look at is the 'Cont Gen Voltage Wfm-Int Clk
non regeneration.vi' This does not regenerate the same waveform in the
buffer but instead creates a new waveform to output after the previous
one has been written to the buffer.
It should be noted that there may be some gliltching if you are
updating the waveform. This is because the buffer will already have a
waveform in there to output before you input the new one so a new
frequency may not have an exact number periods that fit into the
pre-defined buffer. If you are looking to generate dynamic waveforms
then the best option for the best results would be one of our arbitrary
waveform generators here.
Good Luck,
LeeM
NIUK

PXI 6713

Hi All
I have been tasked with writing a LabView application to test the functionality of all the input and outputs of a PXI 6713 module. All was going well until I tried to get an output from the 'FREQ OUT' and 'EXT STROBE' pins. User manual briefly mentions these pins as outputs but when I try to configure in DAQmx they are not selectable as physical channels. Can someone please tell me how to configure them to give an output that I can measure.
I'm using LabView 2011, MAX 5 .0 and DAQmx 9.3.5
Thanks in advance

Hi Ian,
If you consider the old usual manual, then there is a little more information on the two outputs you are referring to, that might prove useful:
FREQ_OUT Signal
This signal is available only as an output on the FREQ_OUT pin. The
frequency generator for the 6711/6713 device outputs the FREQ_OUT pin.
The frequency generator is a 4-bit counter that can divide its input clock by
the numbers 1 through 16. The input clock of the frequency generator is
software-selectable from the internal 10 MHz and 100 kHz timebases. The
output polarity is software selectable. This output is set to tri-state at
startup.
EXTSTROBE* Signal
EXTSTROBE* is an output-only signal that is used for controlling SCXI
devices.
There is also a table in this document specifying information about the inidividual inputs and outputs that could also prove useful.
Let me know how you get on, or if you require any further information.
Kind regards,
Matt H
Applications Engineer
National Instruments UK

Does PXI-6713 have a 50 ohm impedance and capability to go from 0-1 volt

does PXI-6713 have a 50 ohm impedance and capability to go from 0-1 volt?
Thanks!

Hello,
According with the specification (the help file can be download on Analog Output Series Help (User Manual and Specifications))
The Voltage Output Impedance is 0.1 Ohms
The Output Range is +/- 10V or +/- AO ext ref.
Best regards,
Nick_CH
Attachments:
Voltage Output Specifications.JPG ‏13 KB

Generating a square waveform of 100 KHz from one of the Anolog output channels of PXI-6713 ?

Hi
I am trying to generate a square waveform from one of the anolog output channels of PXI 6713.
I am developing my application in VC++
My requirement is a continous 100 KHz square waveform with 90% duty cycle and 1.5 V amplitude.
The following is the code i have used (i have removed error handling code):
***** code *******
i16 deviceNumber = 6; // PXI 6713 Device Id as per NI-MAX
i16 deviceNumberCode; // to be returned by Init_DA_Brds function
i16 chan = 2; // DAC channel 2
i16 numChans = 1; // only one channel is used for
i16 chanVect[1] = {2}; // DAC Channel 2
f64 gain = 1.0;
i16 binArray[10] = {0};
i16 group = 1; // default for most of the devices
u32 count = 10; // 10 data points
// 9 data points ON and 1 data point OFF constituting 90% duty cycle
f64 voltArray[10] = {1.5,1.5,1.5,1.5,1.5,1.5,1.5,1.5,1.5,0};
u32 iterations = 0; // Repeat waveform indefinitely
i16 mode = 0; // Disable FIFO mode / delay mode
f64 rate = 100000; // 100,000 points / sec
i16 units = 0; // points / sec
i16 timebase;
u32 updateInterval;
i16 whichclock = 0; // update clock
i16 operation = 1; // Start waveform initiation
Init_DA_Brds (deviceNumber, &deviceNumberCode);
WFM_Scale (deviceNumber, chan, count, gain, voltArray, binArray);
WFM_Group_Setup (deviceNumber, numChans, chanVect, group);
WFM_Load (deviceNumber, numChans, chanVect, binArray, count, iterations, mode);
WFM_Rate (rate, units, &timebase, &updateInterval);
WFM_ClockRate (deviceNumber, group, whichclock, timebase, updateInterval, mode);
WFM_Group_Control (deviceNumber, group, operation);
If I try to generate 10 KHz waveform with the same 90% duty cycle and 1.5 V amplitude, the waveform gets generated continously....
But for 100 KHz, itz generating continously....but only few waveforms....
Is there any hardware limitations ? I've tried changing the value of the timebase ( points / sec) and update interval etc...
plz help me
thanx in advance
sriram.

Sriram;
The best way to get started is to run one of the NI-DAQ shipping examples. You can find a good example at
C:\Program Files\National Instruments\NI-DAQ\Examples\VisualC\Ao. Take the one named WFMDoubleBuf.c.
On that example, you will just need to change the data written to the buffer to met your application's pulse train requirement.
Hope this helps.
Filipe A.
Applications Engineer
National Instruments

How to measure a current signal with NI 6211?

How to measure a current signal with NI 6211?

Hi Clecio,
This is a charge accelerometer. It is different from the IEPE accelerometers that outputs a voltage signal.
You need a charge amplifier. Then according to the charge amplifier output we can select an appropriate module to measure the signal.
It is not possible to measure charge accelerometers with NI 9234 directly.
Best Regards,
Rodrigo Schneiater
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If this information was useful, please click in the 'KUDOS!' beside.

Better estimation of phase difference between two signals with variable frequency!

Hello LabView Gurus,
Being a power engineer and having just a little knowledge of signal processing and labview, I have been pulling my hair out for the last couple of days to get a better estimation of phase difference between two signals.
We have two analog voltage signals; 1. sine wave (50Hz ± 1Hz) and 2. a square wave with exactly half of sine wave frequency at any time.
At the starting point of operation (and simulation/acquisition) both signals will have no phase difference. However, the square wave's frequency changes unpredictably for a just a few millisecond but then it gets synchronized with sine wave's frequency again. This means that the square wave will be phased out from its original position. The task of the labview is to find the phase difference between the two signals continuously.
My approach to determine the phase difference is to measure the time when sine wave crosses zero amplitude and the time when the very next square wave changes amplitude from zero volts to +ve voltage (I have a 0.5volts threshold just to avoid any dramas from small line noise). The difference between these times is then divided by the time period and multiplied by 360 to get this phase difference in angles.
As this part is just a small block of a big project, I can only allow 5000Hz sampling rate each for both signals. I read 500 samples (which means I read data from 5 cycles of sine wave and 2.5 cycles of square wave).
Now the problem is, as long as the frequency of sine wave stays constant at exactly 50Hz, I get a good estimation of the phase difference but when the frequency changes even a little (and it will happen in the real scenario i.e 50Hz ± 1Hz and the square wave's frequency is dependent of sine wave's frequency), the estimation error increases.
I have attached my labview program. From front panel, you can set the phase of square wave (between -180 and 0) and you should see the labview's calculated phase in the indicator box named 'Phase'. Then you can press 'Real Frequency' switch that would cause the frequency to change like it would in real operation.
You can observe that the estimation error increases after you push the button.
All I need to do is to reduce this estimation error and make it as close to the actual phase difference as possible. Any help would be greatly appreciated.
I am using LabView 2009 for this task.
The application is for electric machines and the stability/performance of machines under different faults.
Thank you for reading this far!
Regards,
Awais
Attachments:
v603.png ‏320 KB
v603.vi ‏186 KB

Jeff Bohrer wrote:
Basic math gives me a bit of pause on this approach. You are sampling at 50 times the frequency of interest so you get 50 samples per cycle. your phase resolution is 1/50th cycle or 7.2 degrees +/- noise. You will need to samlpe faster to reduce phase resolution or average multiple readings (at a time cost that is signifigant)
Jeff- (Hardly Working)
I am sampling at 100 times the sine wave's frequency and 200 times the square wave's frequency. Increasing the sampling rate completely solves my problem. But since I am acquiring several other inputs, I cannot afford a sampling rate higher than 5kHz.
F. Schubert wrote:
I'm not a signal processing expert, but here my basic understanding.
If you simulate sampling with 5kHz and a frequency of 50 Hz (and both are 'sync' by design), you always get an exact 5 periods. Any variation of your signals frequency gives you a propability to get 4 or 6 'trigger' events. That's an up or down of 20%!
The one measure to reduce such problems is using 'window functions'. They don't fit your current approach (counting instead of a DSP algorithm), so this needs to be reworked as well.
My approach would be to use the concept of a Locki-In amplifier. You need to phaseshift your ref-signal by 90°. Then multiply your measurement signal with the ref signal and the phase shifted ref signal. The obtained values for x/y coordinates of a complex number. Calculate the theta of the complex number (with the LV prim). Feed this in a low pass filter.
The trick on this is, that the square wave has harmonics in it, in this you are interested in the second harmonic which is the sine wave.
To get rid of the effect that the sync between sampling rate and ref signal frequency gives an error, you then can use the window I mentioned above (place it before the lock-in).
For a design that really plays well, use a producer-consumer design pattern to get the calculations done in parallel with the DAQ.
I suggest you to check on wikipedia for some of the keywords I mentioned. Go also for the external links which lead to great tutorials and AppNotes on the signal processing basics.
Sorry, it's not a simple solution I offer and we will have quite some conversation on this forum if you follow this path. Maybe someone else knows a simpler way.
Felix
www.aescusoft.de
My latest community nugget on producer/consumer design
My current blog: A journey through uml
An interesting view. the sine wave can indeed be looked as a second harmonic of the square wave. I will implement your idea and get back to you as soon as I get some results. But since I have very limited knowledge of signal processing, it might take me a while to get my hear around the solution you mentioned.

Analog signal from PXI

Hi everybody,
I have a problem: I cannot acquire 6 analog signals with a PXIe 8135 with 4MS/s. I use two boards with 4 MS/s, 16 bits and 8 Analog Inputs. I use a subVI of SAMPLE CLOCK for configuration with this parameters, Continuous SIGNAL, SAMPLE RATE = 4MS/s ( see attachment ). With one signal is ok, but with 2 signals, i have an overload Memory Message.
Where is the problem in the VI?
Thanks for your help.
Attachments:
acq_and_graph.zip ‏165 KB
acquire&loggdata.png ‏230 KB

Quickly looking through your code now, try removing the "Number of Samples analog". Since you are using Continuous Samples, you are just limiting the buffer and also limiting how many samples you can read at a time.
But you might want to think about using Finite Samples. You know how long you want to log for and you know your sample rate. So why not just do the simple math and tell DAQmx to get that many samples? You can use the DAQmx Task Done? VI to see if it is done. That would be much simpler than checking the time that has elapsed.
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Aquisition of a voltage Signal with PXI 6713

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