Amplitude and level measurement two signals

Hello,
I am delveloping a data aquisition VI, I am using the DAQmx and it works fine. I am using the amplitude and measurement express vi to obtain data such as peak to peak etc... I can aquire up to eight channels using the DAQmx, just by selecting the physical channels, but the amplitude and level measurement vi only seems to give me the value of one of the signals (the first one aquired), even though two are being displayed on the graph or even three. How can I display all the peak to peak values for all waveform simultaneously. I am aware that the measurement express is a dynamic data type and conversting the output into an array would work, but I keep on getting errors. Any advice. Attached is the VI and a snapshot of the VI. I also tried splitting the signal with no luck.
Thank you
Attachments:
run.JPG ‏152 KB
Cont-Acq-and-Graph-Voltage-Int-Clk6.vi ‏144 KB

HI Tareq,
Well I think I tired what you said but it is still not working, here is a snapshot of my VI and the VI itself. I still get the same output
Thank you for your help
Alloush
Attachments:
Cont-Acq-and-Graph-Voltage-Int-Clk7mod.vi ‏145 KB
run.JPG ‏160 KB

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Amplitude and level measurements for stereo signal

Hi,
If I input my attached stereo file into Express Amplitude and level measurement (blue icon) it does not give me output value as an array. I want to measure peak to peak value for both left and right channels. I get only left channel value. (No array)
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I have attached my audio file.
Sheetal
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AUX_HP1_RSA_OFF.zip ‏13 KB

Sheetal,
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Amplitude and level

Dear sir
What is the difference between amplitude & level measurement with vibration level measurement? I found both has measurement such as RMS and Peak value, but it gave a quite different value when I try it simultaneously.
Can I used the amplitude & level measurement to measure vibration level?

Product differences:
Amplitude and Levels Step is activated by SignalExpress
Vibration Level Step is activated by Sound and Vibration
Functional differences:
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Amplitude and Levels Step supports measurement of DC
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Hello,
       I have been having a frequent error with a VI in a program I am using. The specific error is:
Error-20312 occurred at "ma_ptmFetch.vi" when called from "Amplitude and Levels N chan.vi"(waveform index 0 of 4)
Possible reasons: The input waveform is zero.
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Hello Mike,
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Thanks,
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Good Morning,
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Can counter measure pulse width difference between two signals

I am interested in determining the high pulse width time that two signals have when they are in various phases between eachother.

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I need to determine the time period between two pulse signals. I'm going to assume for now that I can get these pulses as TTL.
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Solved!
Go to Solution.

Hi CAS,
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Alternate Approach 1:
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Alternate Approach 2:
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You didn't mention what frequency you would be using, but X Series have on-board FIFOs which will help you avoid errors from samples being overwritten if your external frequency is relatively fast.
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Best Regards,
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Hello!!!how can I control an omron plc (sysmac cqm1)with an OPC server?I want to adquire a signal controlling its amplitude and frecuency.How can it be done with OPC server?I already have the NI CD of OPC drivers.Thank you

Hello!!!how can I control an omron plc (sysmac cqm1)with an OPC server?I want to adquire a signal controlling its amplitude and frecuency.How can it be done with OPC server?I already have the NI CD of OPC drivers.Thank you

Hola Jose David, que OPC estas utilizando?, Si tienes comunicación entre tu computadora y PLC pero falla la comunicación entre el OPC y el PLC? La configuración y direcciones entre los dos es correcta? La comunicación es por cable serial?
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Saludos
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How should I set the parameters of PID Autotuning such as relay amplitude and PV noise level?

I want to control the temperature of a room by changing the hot water flow of a radiator with a control valve. The desirable control accuracy is +/- 0.5 degree of centigrade.
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Generat two signals at the same time and reading voltage

Hii
i have try to generate two signals at the same time and read voltage from another port on the board(not have to be at the same time), i have not alot of expriens in labview
and i based my code of example(http://zone.ni.com/devzone/cda/epd/p/id/5197) from yours site and try to suit to my needs
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Possible reason(s):
Specified route cannot be satisfied, because it requires resources that are currently in use by another route.
Property: RefClk.Src
Source Device: Dev1
Source Terminal: 10MHzRefClock
Required Resources in Use by
Task Name: _unnamedTask<0>
Source Device: Dev1
Source Terminal: None
Destination Device: Dev1
Destination Terminal: RefClock
Task Name: _unnamedTask<1>
eyal

sorry...
The AO tasks is very important they will be synchronize ,it is very importent the two tasks will start at the same time
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first of all i make the two signals(synchronize signals).
and after it i will need to reading voltage.
i can make two signals synchronize together.
i can make reading voltage
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eyal
Attachments:
test11.vi ‏130 KB

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.
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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%!
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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.
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www.aescusoft.de
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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.

How to measure two frequency simultaniously in a PCI 6014

Hi I am measuring RPM of two gear drives by measuring the pulse/second(Measure frequency.vi). I have interlinked the gate of counter1 to the output of counter2. Similarly I have connected the gate of counter2 to output of counter1. to measure frequency.
This way in a cycle one counter acts as gate counter while the other counter counts and later the counters changes their role.But my problem is that I have to measure the two counters frequencies simultaniously.
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3) Would this be a accurate method for measuring frequency simultanuiously without using two counters?
Thanks.

Hi balajkasthuri,
The best way to perform this is to use the frequency generator (freqout) of your 601x board. Your board only has 2 counters but it also has a frequency generator that doesn't use the counters. It is an output found on the freqout pin. You can choose to have a frequency of 10 MHz or 100 kHz divided by any integer between 1 and 16. This means you can create a pulse train of known frequency and known period and use that into the source or gate of your two counters depending on the frequency measurement method you are using.
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Otherwise, if your signal is much slower than 20 MHz, you can simply use the 20 MHz as the source of the counters and perform a simple period measurement on your signal. You would then take the inverse of your period measurement.
Anyway, using the onboard frequency generator will give you the flexibility you need. I have linked below a useful tutorial describing the 3 typical frequency measurements. Hope that helps. Have a good day.
Making Accurate Frequency Measurements
http://zone.ni.com/devzone/conceptd.nsf/webmain/CD2C8AAED8FA59A486256C230078FE75?opendocument
Ron

Can you tell me how to measure audio signal frequency in measurement studio with visual basic 6.0?

I'd like to measure two differential input signal(I.e. A+ and A-),below is two test projects,
1.connect A+/A- to PCI 6052E card's ACH0/ACH8 ,and refer to GND for testing
2.connect respectively A+/A- to PCI 6052E card's ACH0/ACH8 for testing
Could you tell me the details of the second project?and give me a illustration in measurement studio with visual basic 6. 0 about the second?
In addition,I would like to measure the audio signal frequency,could you give me a illustration in measurement studio with visual basic 6.0?
Wait for your reply!

Dear kelven,
Thank you for contacting National Instruments.
To address your question, there are Analog Input shipping examples that demonstrate how to measure an analog input differentially, as you specify in (2).
As for measuring the audio signal frequency, you may want to check out the following KnowledgeBase. The link is:
http://digital.ni.com/public.nsf/websearch/4b08380530d72d3b86256340004c3005
Let me know if you have any further questions or if this does not resolve your issue.
Thanks again and have a great day!
Chad AE
Applications Engineer - National Instruments

Amplitude and level measurement two signals

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