Measuring AC voltage in Labview 8.5

I have all my channels set up fine in MAX and the hardware is working correctly. I'm trying to measure the power as a function of voltage and resistance but my voltage is ac and I'm not sure how to get a single value through the vis. When I try using a DAQ Express VI or virtual channels it gives me 24 regardless of the input voltage. In MAX it does change and gives me a waveform. I am fairly new to the labview environment.

Are you just reading 1 sample? What is the frequency of your signal? What is your sampling frequency?
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Can I measure the analog USB supply voltage using Labview?

I'm basically powering a sensor from the 5V (nominal) USB supply but the full scale output depends upon the actual input voltage for any particular measurement- what I want to do is get labview to measure the voltage at the USB port at the same time it samples the sensor voltage output then from that the full scale output for that instant in time can be calculated and thus give a more accurate measurement. Can this be done in labview? Thanks very much.
Haydn Barker
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There is no such hardware feature that is universal to all motherboards. Additionally, depending on the current being used, the length of the usb cable, etc. the voltage present at your sensor would also vary, probably a lot more than the 1% accuracy. I know that some motherboards have onboard monitoring of key voltages, but think it more at the the "main 5V" level, not individual usb ports.A USB DQ device may be the only way to actually measure the supply voltage at the sensor.
Putnam
Certified LabVIEW Developer
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Currently using LV 6.1-LabVIEW 2012, RT8.5
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When measuring 6 voltage signals in labview I found that there was a difference in voltage signals in my program but not in the test panel. The test panel is correct. What is wrong with my program?

My labview program is not displaying equivelent voltages, but labview test panel is. So the computer is seeing the correct signals. My program is displaying a small difference in 3 out of 6 channels. All channels should be equal.

G'Day Pops,
You haven't really given us enough to go on - could you please post your VI so we can have a look at it?
cheers,
Christopher
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Can I measure AC voltage using FP-AI-102? I want to measure in the range of 0-120 VAC

Can I measure AC voltage using FP-AI-102? I want to measure in the range of 0-120 VAC

Hello Luis,
The update rate on the AI-102 module is 360Hz, which means that you can only accurately acquire waveforms with frequencies below 180Hz.
FieldPoint wasn't made for high speed measurements, so you will have to make sure that you are able to acquire the waveform you want to with the hardware that you have.
If you want to know how you would do the acquisition, I urge you to take a look at the LabVIEW shipping examples.
Help»Find Examples... and browse to Hardware Input and Output»FieldPoint»Analog IO
As for writing to the file, you can take a look at examples under Fundamentals»File Input and Output. You can use the functions included in the Functions Palette under Programming»File I/O.
I hope that this helps!
Kameralina
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Measuring network voltage

I have scxi 1327. The gain is set to 1/100, so when i measure AC Voltage directly from the grid i have max 303V instead 222*sqrt(2)=313V (the grid voltage measured by a multimeter is 222V). In Measurment and automation studio everything is set correctly. Is it something about the max voltage that i can measure or... Thank you

Hello;
The multimeter will give you the RMS voltage of the measurement, while MAX and Labview will give you the actual instant value, which will register all picks of ths waveform that is being read.
Regards
Filipe A.
Applications Engineer
National Instruments

Measuring DC voltage

Hi Am trying to Measure the Voltage of a 9V Battery.After disconnecting the battery the value of the voltage in the indiacator in the VI goes down very slowly instead of falling to zero immd.Am using AI sample channel.vi to get the output from the virtual channel.How can I bring it down to zero as soon as the battery is disconnected?

I´m using LabVIEW 8.0 with Real Time 8.0 and a Desktop PCs as RT Target.
In the host.vi, I have a Waveform Chart, and a cluster with four double controls to pass the values of the Frequency, Offset and Amplitude. I have created with the cluster a custom shared variable.
In the traget I have within a Timed Loop the Simulated Signal.vi and a Shared variable, double one. I have selected both shared variables to be Network-Published, and the period of the Time Loop is 1 ms.
I intend to be able to change the senoidal waveform´s amplitude and frequency while running, but I don´t get any value. I have reproduced the vi to run just under the LabView in local mode, without the RT target, and it works fine, although I can not get the frequency to mach the time...
Any idea why my system does not work.
Simbani

I'm trying to set up a DAQ assist just to measure some voltage, how do i get the graph to start from 0 (time) every time I press run

Hi all,
I am trying to set up a simple DAQ assist to measure some voltages (currently a 9 volt battery to aid set up), when choosing to use a waveform chart to log the voltages the graph doesnt start from 0 (time seconds) how do I do this and get it to reset every time I press run or even stop.
What I want to see at the end is a chart for the full lenght of the test showing voltage against time in seconds.
Any ideas peeps
many thanks
Shane

Hi Shane,
Look at this VI
Here, I clear the chart before running the VI, using a 'history data' property node ( i pass an empty array to clear it)
In effect, each time you run the VI, the chart will begin at 0:00
Hope this helps
Regards
Dev
Attachments:
chart_start.vi ‏20 KB

What's the maximum output voltage of labview

hi
i want to give 0 to 10v to the oscillator circuit so for that i would like to know that maximum output voltage of labview because i want to oprate my oscillator using labview program

hussey,
this discussion has no worth.
We KNOW that you want to generate voltage using the programming language LV.
Since no programming language in the world is able to generate voltage without dedicated hardware, repeating "I want to use LV to generate voltage" several times will not bring you anywhere.
What kind of hardware do you have for voltage generation mounted in you PC?
What else do you want to generate except DC voltage (controlling an oscillator could include also AC voltage stimulation...)?
Norbert
CEO: What exactly is stopping us from doing this?
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Can the analog inputs be daisy chained to measure higher voltages?

Can the analog inputs of a PXI-6289 be connected in series to measure higher voltages than normally allowed at the analog inputs of the PXI-6289 (i.e. 10 VDC)? For example, let's say I wanted to measure 18 VDC using an analog input channel of the PXI-6289. I would then pick two AI channels and connect the positive of one to the negative of the other and then the two remaining leads would be placed across the 18 VDC. Resistors could also be placed across the 18 VDC to form a votage divide. One AI would measure the voltage across one resistor and the other AI would measure the voltage across the remaining resistor. I have tried this and the voltage measurements appear to loose accuracy. Thank you for your help.

Hello Rafi,
You may want to invest in a high voltage attenuator for signal conditioning prior to reading the signal. The documents below may also be helpful:
High Voltage and Isolated Measurements
http://zone.ni.com/devzone/cda/tut/p/id/10693
High-Voltage Measurements and Isolation
http://zone.ni.com/devzone/cda/tut/p/id/3410
Regards,
Roman Sandoval | National Instruments | RF Systems Engineer

Trouble using one Keihtley 2400 to preform a current sweep to drive a laser diode and use a second to measure a voltage from a laser power meter.

I am trying to drive a laser diode with one 2400 Sourcemeter using a current sweep, while simultainiously measuring the voltage of the analog output of a Thorlabs Pm100a powermeter. I have been attempting to cobble together the triggered measurments example with the sweep and measure example, but I cant quite figure it out.
Attached is the franken-vi I have created.
Any help is greatly appreciated.
Dan R

Are you getting any error codes when trying to run this modified VI? What are the results when running?

MSI 6600GT AGP - Measured fan voltage

I wanted to know exactly what was going on with the fan on my MSI 6600GT AGP so I measured the voltage. The fan runs at a constant 12 volts even under load. No matter what temperature the card is the fan runs at full rpm's.
I'm not sure if this a change from earlier revisions, because this is my second 6600GT. The fan on the first one seemed to vary the fan speed going by what I heard, but I never had a chance to actually measure it. So I could be mistaken and it also was running at full rpm's all the time.

Quote from: Glenn on 27-February-05, 07:49:55
I had the exact same thing happen with my X800 but in reverse, the one I currently have seems to vary fan speed, I can tell at startup, the fan is pretty loud, at first I thought it was my burner but after investigation, I see that it is my card. My son has the other one and it runs constant, but it isn't much louder as I remember. He has case fans that are louder.
For me, it's a no care item. That may be a different story for you.
I'm glad it is running constant because if it wasn't I was ready to mod it. It's not loud at full voltage either so its better all around IMO.

Is it possible to measure ac voltage using cFP-AI-100?

I have the cFP-AI-100 module.. is it possible to measure ac voltage with this analog input module?
Is there is any specific module?

Hi ELUE,
I will need a little more information to give a good recommendation. What range of voltages will you be measuring?
The following link will bring you to all the analog input compact FieldPoint modules we have:
http://sine.ni.com/nips/cds/view/p/lang/en/nid/11575
Other things we need to consider is what frequency the signal will have, and if we need isolation between the channels. Any further information would help. Have a good day.
Brian K.

Measuring the voltage of series connected batteries

Hi, I am using the ADC of PIC18 to measure the voltages of the battery bank in which the batteries are connected in series. I have to measure the voltages of each battery in the bank. I am using differential op-amp with voltage divider to bring the voltage into the range of the ADC. Now as the batteries are connected in series so when I connect it with the circuit it is measured as zero. while not connected in series the measurement is fine. I need soluton for this problem any help will be greately appreciated. what should I do to measure the battery voltages while connected in series. Thanks
If you are young work to Learn, not to earn.

Do you have a wiring diagram or circuit to show your setup?
What is the voltage of the batteries? What is your supply voltage for the Op-Amps? How many batteries?
What I'm guessing is that the common-mode voltage of the battery is higher than the supply voltage and therefore both sides of the differential op-amp are railing and therefore no difference.
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CV measurement with HP4275A and Labview

We are currently using HTbasic interact with HP4275A to do CV measurements. The HTbasic program occasionaly lockup. I wonder if anyone write VIs to do the same type of mesurement as HTbasic does. Please point me to where I can download VI example to do CV measurement.

Look on your LabVIEW Instrument Driver CD or download it here.
Message Edited by Support on 11-20-2007 02:45 PM

How can i measure a voltage with the digital i/o port on my nudrive using labview?

I am using a 4SX-411 nu drive to control my stepper motor. I need to measure an input voltage at the digital I/O port of the nudrive. How can I program LabVIEW to do that?
Thanks

Hello Raven24,
Thank you for contacting National Instruments. NUDrive 4SX-411 is a value motion drive and you can connect to it using any of the ValueMotion boards. When using a ValueMotion NUDrive with steppers you have I/O ports 1-4 available for general purpose use, I/O ports 5-8 are reserved for axis inhibit output signals. Refer to section 4-7 of the ValueMotion Hardware User Manual linked below, for information about the jumper settings.
ValueMotion Hardware User Manual:
http://digital.ni.com/manuals.nsf/websearch/6CF7A54E0BDEA1388625665F0054FFDF?OpenDocument&node=132090_US
Once you have setup the jumpers appropriately, you can use the VIs found on the ValueMotion I/O & Limits pallet for configuring and using the I/O channels. Search for "I/O" in the attached help file for more information about these VIs. I hope this helps you out. Have a great day!
Regards,
Nipun M
Applications Engineer
National Instruments

Measuring AC voltage in Labview 8.5

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