Acquiring DC Voltage Signal from HP3457

I have a question that I believe to be easy to solve. I am using LabVIEW to acquire DC Voltage from a HP3457A DMM. I can acquire the signal OK, but when I write the data to an lvm file only about every 8th measurement is correct (with the others being way off!!) I am using a modified VI from LabVIEW for the 3457. I have modified it to sample every second, plot the data, and write it to an lvm file. Anyone have any experience with this or any idea what may be going wrong here. Thanks in advance for all of your help.
Attachments:
3457.vi ‏132 KB

Hello,
I checked the VI that you sent and the only thing that I could see is not proper is that the LVM file is open and close every time you write to it but that doesn�t seem to be the problem.
I removed the GPIB part and sent a constant number and it worked ok in the LVM, so I believe the problem is acquiring the data.
I would suggest you to remove right now the LVM part and first make sure that the data acquisition is working ok. Just extend the output of the converter from string to number outside the loop, enable indexing and create an indicator. Stop the vi and make sure that the values that you see are the correct ones.
Hope this troubleshoot helps.
Ricardo S.
National Instruments.

Similar Messages

Acquiring AC voltage signal using NI 9206 9205 and cRIO

Hello. I am having difficulty accurately acquiring an AC voltage signal using a NI 9206 and cRIO. I'm attempting to acquire voltage signals from two types of Magnelab Current Transformers: split core and rope. In Labview, I first populate an array of size 2,500 with the sensor signal (DIFF mode), then compute the RMS of the array. For the split core CTs, I am able to accurately acquire the correct voltage reading (verified by measuring the corresponding amp on the line using a Fluke 434 Power Analyzer. For the rope CT, however, using the same array/RMS method, I am unable to accurately acquire the correct voltage reading. Measuring the amp on the line using the Fluke 434 PA, the correct voltage from the rope CT should be 0.05v. Using the 9206 (DIFF mode), the RMS from the array gives a voltage reading of 0.071. Now the interesting part is when I measure the line voltage using two different True RMS DMMs, I get two different readings. One multi-meter, a Klein CL2000, reads the correct voltage at 0.05v. Another multi-meter, a Fluke 189, reads incorrectly at 0.071, the same as I get using LabView and the NI 9206. I suppose the question is how is the Klein interpreting the signal differently than the Fluke 189 and the NI 9206 via LabView. One difference between the split-core and rope CTs is that the rope CTs require an external power supply 12-30v AC or DC. I am providing them with 12v DC. I have tried multiple voltages in both AC and DC and still get the same incorrect reading. I'm quite certain it is not a power supply issue, although perhaps the integrator in the rope is creating a unique signal. Any ideas? I appreciate any input.
Thanks,
J.Grant
Solved!
Go to Solution.

AK2DM:
Update - solution found
While the Butterworth low-pass filter sort of worked, it was NOT the solution. I spent some time analyzing the rope CT signals by sampling at a very high rate. The AC signal coming off the rope CTs is triangular NOT sinusoidal. The RMS function in LabView assumes a sinusoidal waveform and essentially calculates the RMS as the average of voltage peaks (for each cycle) / sq.rt (2). Since the AC voltage single emanating from a regular split-core CT is basically sinusoidal, the LabView RMS of the signal gives an accurate reading of the voltage signal. Unable to find a RMS function in LabView for a triangular AC voltage signal, I ended up developing my own custom triangular RMS function in LabView. My function analyzes the signal by finding the peak of every cycle within the signal, takes the average of these peaks, then divides this average peak by sq.rt (3). see this link for formulas:
http://www.optics.arizona.edu/nofziger/OPTI%20380B/Lab%201/AVG%20and%20RMS%20Values%20of%20Periodic%...
Using the triangular method, I am able to accurately acquire the signal off the rope CTs.
Thanks for your help!

Acquiring and analysing signals from a wave (.wav)

Hello everybody,
I would like to acquire the two signals from a stereo (.wav) file and perform a Cross-Correlation between them.
Where can I find similar examples?
I’m an absolute beginner in Lab-VIEW 7.1 and would appreciate any help.
Thank you

This VI converts any .WAV file into waveform data for further processing in LabVIEW. The VI returns the file as a waveform as well as information about the sound format of the .wav file. The components of sound format include sound quality (mono or stereo), rate (8000, 11025, 22050, or 44100), and bits per sample (8 or 16).
Attachments:
WAVFILE.LLB ‏614 KB

I have an NI5911 high speed digitizer and would like to acquire a video signal from a CCD using it. Does anyone know if this is possible without buying any more hardware please? If it is, how would I go about it?

The only thing I succeeded in finding on the NI site was about using a different high-speed digitizer in tandem with an IMAQ card but I was hoping not to have to buy an IMAQ card as it means I may as well not have got the NI5911 (a while ago) in the first place. Any help would be greatly appreciated!

You can certainly acquire video signals with the 5911. The only tricky part is that the 5911 does not have any video triggering options. That means that you will have to either find a way to provide your own trigger based on the video signal (that's where the IMAQ board comes into play) or you can just take a lot of data and keep only the data you need once it is in software. For instance, you could take one large record and then use software analysis to determine where the frame sync occurs. Hopefully this was helpful.

How can i find the gain/amplification factor used when acquiring a voltage signal using PCI 6036E

in short, i am interested in find the sensor gain for used in feedback loop simulation

Greetings!
The gain setting defaults to unity gain, but it is selectable to x10 or x100, also. (This is your pre-digitizing gain, of course...after it's in digital form, you can tweak the gain to anything you want in your VI.
Hope this helps.
Eric
Eric P. Nichols
P.O. Box 56235
North Pole, AK 99705

Acquiring signal from PCI 1428 card

Hi,
I'm new to labview and been tryig to acquire the trigger signal from the PCI 1428 card. Is there anyway to acquire the trigger signal internally without using an external cable (breakout cable)? Can labview acquire this signal without using the external DAQ card?

Hello DjBiomed,
It may help if you can provide more information regarding your application. What are you ultimately trying to do with this trigger signal? With the 1428 trigger line, it needs to be wired to something (either externally or through RTSI). LabVIEW cannot automatically detect this unless it is connected. You can look at the trigger examples that come shipped with the driver in the LabVIEW Example Finder for a better understanding. They can be found on the browse tab under Hardware Input and Output >> IMAQ >> Signal Input and Output. I hope this helps.
Vu

Acquire signals from a monitor

How does one acquire the physiological signals from a medical monitor? The monitor is a non-national instruments monitor. The patient monitor records ecg, invasive blood pressure from a patient and displays this on a screen. This information is relayed to a central station. Is there a way to obtain these signals and see the ecg and blood pressure waveforms in labview and thus analyse these waveforms. Thank you

Sssantosssh wrote:
How does one acquire the physiological signals from a medical monitor? The monitor is a non-national instruments monitor. The patient monitor records ecg, invasive blood pressure from a patient and displays this on a screen. This information is relayed to a central station. Is there a way to obtain these signals and see the ecg and blood pressure waveforms in labview and thus analyse these waveforms. Thank you
Is reading the manual for this medical monitor something you are not capable of doing?

How to send TTL output AND acquire AI voltage data using USB-6211

Hello,
I am relatively new to Labview, so please bear with me. I have a research application involving 2 pressure transducers and a high-speed camera. I wish to acquire analog voltage data from the 2 pressure transducers. However, at the start of the acquisition, I will need to send a single TTL output to trigger the camera. This TTL pulse must be sent out at exactly the same time that the AI acquisition begins, in order to ensure that my 2 pressure measurements and camera images are 'synchronized' in time.
Is this possible on the USB-6211 running with LabView 8.20? I currently have a fairly simple LabVIEW vi that uses a software trigger to start an AI acquisition - I have attached it with hopes that it may help anyone willing to assist me. I would prefer to be able to simply add something to it so that it will output a TTL pulse at the start of the acquisition.
Thank you in advance.
Regards, Larry
Message Edited by Larry_6211 on 12-19-2008 11:24 AM
Attachments:
USB6211_v1.vi ‏212 KB

Hi All,
I'd like to clear a few things up. First, you'll find that if you try to set the delay from ai start trigger and delay from ai sample clock to 0, you'll get an error. Due to hardware synchronization and delays, the min you can set is two. Note that when I say two, I am referring to two tick of the AI Sample clock timebase, which for most acquisitions is the 20MHz timebase. I modified a shipping example so you can play around with those delays if you want to - I find that exporting the signals and looking at them with a scope helps me visualize what is going on. The Manual has some good timing diagrams as well but it looks like you've already hit that. The defaults would give you a delay of 250ns from the start trigger - is this too high for your situation? What is an acceptable delay? I tend to think that "exactly the same time" is a measure of how precise rather than an absolute (think delays in cable length making a difference.)
With all that in mind, I see a few options:
Start your camera off of the AI start trigger (an internal signal) and just know it is 250 ns before your first convert.
Export the convert clock to use as a trigger. This assumes your camera can ignore the next set of convert clocks.
More complicated option: Internally you have an ai start trigger, sample clock and convert clock. From your start trigger to the first convert is 250ns but if you export your convert clock you're going to get future convert clocks as well. One option would be to generate a single triggered pulse using a counter (start with the Gen Dig Pulse-Dig Start.vi example) with the AI start trigger as the trigger for the counter, an initial delay of 250 ns, and a high time of whatever you want it to be. This should give you a singe pulse at very close to same time (on the order of path delays) as your first convert clock.
Hope this helps,
Andrew S
MIO DAQ Product Support Engineer
Getting Started with NI-DAQmx
Measurement Fundamentals
Attachments:
Acq&Graph Voltage-Int Clk.vi ‏37 KB

How to use voltage signals as input signals into USB-6211

Hello everyone,
I have a USB-6211 and a PDQ80A -quadrant photo detectot from thorlabs, i am trying to take three voltage signals from the PDQ80A into my PC using USB-6211 from NI. THese voltage signals are X,Y and sum (X+Y).
Looking forward to your reply.
Thanks in advance,
_Perseus

Technically, the question was in the title. But of course, the answer to that is... Connect them using WIRES. It's designed for voltage signals, just wire your cell outputs to whatever DAQ input channels you're going to read.
Using LabVIEW: 7.1.1, 8.5.1 & 2013

Acquire 2 digital signal with custom scaling (Engg Units)

I am a newbie to DIO world.
I have write a VI to acquire 2 digital signals. one from a load cell and other for motor rpm (pulses). I need to acquire these two signals and then convert them into engg units using custom scaling and write them to a txt file with time stamp.
Please suggest best ways to accomplish this task.
Thanks
DAQG
Solved!
Go to Solution.

Look at the examples on DAQmx in the example finder.
You wouldn't actually be acquiring 2 digital signals. You would be acquiring an analog signal from the load cell. A digital or counter acquisition is what you would acquire from the motor. Search for analog measurements and counter measurements in the example finder. Some of the example should show you how to apply the custom scaling.

Negative voltage signal

Hi everybody...
I m using an impact hammer to give excitation to a structure and i m measuring the response using an accelerometer...I want to measure the force with which i m hitting the structure with hammer...For that i am using a multiplier to multiply the voltage signal from impact hammer(in millivolts ) and the sensitivity of hammer namely 2.14 N/mV to get the force value indicated in a indicator....The problem i m facing now is that i m getting this value in negative which should not be so....
Please help me in this regard.....Suggest me possible solutions to arrive at the correct force value....
Awaiting for replies;;;;;

That's right.
     There are several possibilities:
     1.- As they suggested, just invert polarity.
     2.- Most sensors are strain sensors (we don't know what kind of sensor you have). They would generate either positive or negative voltage depending on which side they are bended to. Just like in a weight scale, we calibrate and use the static voltage (whatever it is), then output is positive if depressed, but would be negative if we pull from it. You would just flit over your sensor.
     3.- During impact, the material is bended producing certain polarity, then bounce back producing the opposite polarity. If you just use a digital sampling meter, your measurement will depend on the moment the data is sampled. If you need to record the peak, you also need an analog peak detector, which output is what you're trying to measure. But first, you need to know your polarity.
     Have fun.

Analog signal from Laser Power Meter

Hello,
First, I have to say that I am new using Labview.
Probably for some of you the question I am going to ask is pretty easy, hope you guys can help me solving this.
I am trying to acquire an analog signal from a Fieldmate Laser Power meter, the specifications from this meter are shown in the link below:
http://www.coherent.com/downloads/FieldMateDataSheet.pdf
I need to get the signal and save it in MS Excel files. My big issue is with the acquisition of the signal from the meter to the NI Board. I am using an NI SCB 68.
Hope you guys can help me.
Thanks.

The SCB68 is just a shielded connector block, not a DAQ device.
Use NI's MAX utility (Measurement & Automation Explorer) to find out what DAQ card you have installed in the PC.
There are also plenty of analog acquisition examples that ship with LV, Search Examples in Help.
-AK2DM
~~~~~~~~~~~~~~~~~~~~~~~~~~
"It’s the questions that drive us.”
~~~~~~~~~~~~~~~~~~~~~~~~~~

DAQ of low voltag signal

Hello,
as I´m quite new to LabView and DAQ this question is hopefully easy to answer.
I´m trying to read a voltage signal from a device referring to a temperature ( 10mV = 1°C). When reading the voltage with my DAQ-Card with a rate of 1000 Hz, I see the voltage I expect (300 mV) and peaks with 2,5 V and above 10 V. When I connect to a oscilloscope I can´t see those peaks, but just the right voltage. My question is if this is a problem arising from the small voltage? Does my Card internally amplify the voltage? Do I need to amplify the signal before connecting to the card?
Thanks for your answers!

It should be quite easy for the DAQ-Card to read a 300mV signal at a sampling rate of 1kHz.
I can't explain why you are seeing peaks of "2.5V and above 10V" - this sounds quite wrong - in fact most DAQ-Cards are not even capable of directly measuring anything greater then 10V.
Most DAQ cards will measure using a default range of -5V to +5V (instrumentation amplifier gain of x1) unless you specify otherwise.
In traditional DAQ programming, you specify your expected maximum signal range and LabVIEW/DAQ chooses a suitable board gain to cover at least your signal range. Board gain values are typically 0.5, 1.0, 0.5, 0.2, 0.1, 0.05, etc, etc, although not all boards have as full a range as some others do (it varies depending on cost/specification) - for example, the NI-PCI-6025E low cost board only has gain/ranges of 0.5 (+/-10.0 V), 1.0 (+/-5.0 V), 0.1 (+/- 500 mV) and 0.01 (+/- 50mV).
So to answer your specific questions...
i) No the problem you are seeing is not due to your lowish signal.
ii) Your card can amplify the voltage prior to the DAC (digital to analogue converter) - although you need to program this as you deem appropriate.
iii) Normally you don't need to amplify the signal yourself (except in special circumstances).
Final advice - you should always try to use the default "differential" measuring mode in order to minimise noise - and check to make sure that your signal source is ground referenced to your PC/DAQ board by some route.
Mark H.

How would i acquire signals from a philips viridia patient monitor?

i'm looking for a simple way to acquire patient vital sign trend data
(BP, pulse, etc) from our Philips Viridia patient monitors in the ER.
How can I capture these signals using biobench?

You can use a software application called MECIFView. It uses the MECIF protocol to acquire these signals from certain patient monitors (such as the Viridia). You can download a demo version at http://www.mecifview.com

Generate and acquire signals from Walkie Talkies

Hello, i am a Portuguese Student and i have some problems in a Academic Project.
The following project consists in two Walkie Talkies that are link to a USB 6009.
One of the Walkie talkies are attached do AO0 and ground with the objective of generate a signal to the 6009 then the other Walkie talkie connected to Ai0 and GND have to acquire the same signal that i generate in the other one, this two signals have the main problem that needs to be represented in the same Chart or Graf.
Please can anyone help me in this question and send me a (vi), i would greatly appreciate.
something send me a post or email for [email protected]

Hello Lynn,
Sorry about the late response, but only today i have access again to the USB 6009 in the LAB.
In below are the graph from the input signal, the first is the graph from the Walkie Talkie (receiver) when the button from the Walkie Talkie that send the signal are not press. What we see is only noise and others frequency's.
In the other graph we can see a different graph this graph is from the Walkie Talkie (receiver) but when the button from the Walkie Talkie that send the signal are press where we can see that is a different kind of signal and the receiver are ready to receive the signal and are receiving some signal from the other walkie talkie.
First I need some help for this first steps
1- But how can I generate a signal wave and send it from the other Walkie Talkie (transmitter), I used a Basic Function Generator
2-How can I see in the Walkie Talkie (receiver) if he receive the Signal that I generate in the transmitter, The graph changes of frequency and amplitude always that I press the button of the transmitter Walkie Talkie.
3-How can I put the two signals in the same chart or graph, The main problem is like you said the USB 6009 is too low sending signals.
Sorry my English, I appreciate any help
Thanks
BTP
Attachments:
input data.png ‏33 KB
input receber.png ‏37 KB

Acquiring DC Voltage Signal from HP3457

Similar Messages

Maybe you are looking for