Is inactive analog output will be at high impedance or cut off state?

Hey
I'm using the NI 6229 analog outputs.
I would like to know if there is a tri-state or high impedance state for those analog output when it is not in use?
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Hello amco,
From the description of your project, I'm envisioning two probes attached to different points along a single trace on a PCB.
It is certainly not recommended to have two analog output lines attached to the same channel. As you have experienced, the behavior is unpredictable. In a worst-case-scenario, one could potentially damage the AO line that is not actively driving the channel.
So we do need to find a configuration that makes the unusued AO channel electrically separated from the channel-under-test. One option would be to introduce an electromechanical switch. This will add some complexity to your setup and your code, but it will permit you to send the signal from AO-0, disconnect AO-0, connect AO-1 and send a signal from AO-1 — all in a very short amount of time.
Best regards
Matthew H.
Applications Engineer
National Instruments

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What does analog output do after output

Hi all,
I have a question about the behavior of the analog output on a single AO channel. If I write a single voltage (1.2volt) to an AO channel and keep the operation lasting for 3ms (using delay). I wonder after 3ms, what state will that AO channel be? Will it maintain the same voltage or will be reset (to zero) or whatever?
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An Analog Output will hold the last value until the device is reset or a new value is written. It is advisable to set the AO channels to 0 when you are done with them.
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Question about voltage holding of multi Analog outputs

Hi, I'm programming my NI USB-6008 with V++.
Now I have a question. The device has 2 analog outputs.
When I set channel "ao0" to a certain voltage, then stop this task. Then start another task and set channel "ao1" to another certain voltage. When I do the second task, will ao0 hold the voltage set in the first task?
Thanks.
Solved!
Go to Solution.

Hi Lowsfer-
Yes, the analog output state of AO1 will remain in the last state it was before the task was stopped. As long as the device is not reset or the computer is not turned off, the analog output will maintain the last voltage you specified, regardless of what the other Ao channel is doing.
I hope this helps. Best of luck with your application!
Gary P.
Applications Engineer
National Instruments
Visit ni.com/gettingstarted for step-by-step help in setting up your system.

High Noise on Analog Output PCI 6289

Hi guys
I am using a PCI 6289 M series device for A/D characterization , I am using the device both for the analog output generation and also for data acquistion of the digital lines , The dynamic tests for the A/D were showing a very poor SNR ratio of the ADC, it is a 12 bit adc so technically in the ideal case i should atleast see 90 db but the resulting figure was way lower around 40 db .
I connected the A0 from the PCI 6289 brought out to a scb-68 block to a RHODE and SCHWARZ spectrum analyzer , the above spectrum analyzer is a decent one with good analysis capability and I was surprised to see a SNR of 50 db , the data sheet says that PCI 628X devices have a internal 16 bit DAC so technically the SNR should be atleast 90 db even if 6 db were removed for the harsh environment of the computer .
please advise , have anybody else faced this problem , the data sheet does not give a figure for the SNR ratio of the card , since i need to test a 12 bit adc , thought that 6289 would be up to the task since it has a 16 bit DAC.I am using the Noise shielding cables and also SCB-68 block , the block is far removed from other power supplies .
any ideas why the noise is occuring , one of my colleagues says maybe the harsh environment inside the pc enclosure causes it , is it necessary to use a separate PCI box for the card and then connect the card to the computer , is this standard procedure ?????.
and also does the PCI -6289 have a filtering option for the analog output , all i could find was the filtering for input.

Hi Tom
Thanks a lot for responding to the thread , did not expect a response in the holiday season . The SNR for the 12 bit one was a typo , was referring to the 16 bit onboard dac in the M series card , which technically should ensure a clean input signal having atleast 90 db .
The info you have given helps a lot , i suspect the conditions inside the pc might be causing it , also i am driving the analog output from the card at almost its limits of 2.5 MS/s , the sample rate specification for the card on the data sheet says 2.8 MS/s , also i notice the settling time requirement for the outputs is 3 us which i suspect will put the onboard DAC under quite a load.
If the conditions inside the PC cannot be rectified , where can i find a external PCI box which can be connected to the computer or does such a box exist only for the PXI cards ? will that necessarily rectify the problem and also since filtering is not possible on the card itself , I remember reading the scb -68 connector block has single RC output filter option , i would have to use discrete R,C components to make it but notice on the right hand corner some pcb holes are provided , would this help.
Would appreciate your Response
Thank you
Chip learner

Combine Analog outputs for higher current drive

I'm using a cRIO 9263 analog output module. The current output specification is 1 mA. If I need 1.2 mA of current, can I use two outputs in parallel?
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CLD
FPGA/RT/PDA/TP/DSC

I am not familiar with that device, but, in general when paralleling voltage output devices which were not specifically designed to be paralleled you need to include some ballast resistors. They allow for slight differences in the output voltages of the two (or more) devices and promote current sharing.
Put one resistor in series with each output. Connect the other ends of the resistors together and connect this to the load. The value of the resistors depends on the amount of current, the voltage difference between the two outputs when given the same digital code, how much voltage drop in the resistors can be allowed, and perhaps other factors such as how fast the output must change.
I can help with the calculations if you are not familiar with them, but I will need more information about the voltages and loads.
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How do I configure 128 channels of DIO and 128 channels of Analog output with the availability of 3 pci slots

I have only 3 slots of PCI or 4 slots of ISA bus, I want to configure with the minimum possible modules to attain 128 channels of DIO and 128 channels of analog output. This is inturn fed to the PCM (Pulse code Modulator). The cards will be placed in industrial PC.

Associate Engineer-Marketing,
Using just those 3 PCI slots you're not going to be able to get the 128 analog output channels. You will probably want to go either the MXI-3 (PCI bus extender) to a PXI chassis or E Series DAQ card to a SCXI chassis for such a high channel count system. Which analog output cards and which digital I/O cards you will want depends on your application. You will have to decide whether you will need static or dynamic analog output as well as whether you need clocked digital I/O or not. I highly recommend contacting our internal sales department at 1-800-433-3488. They are great at helping specify systems.
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Loop in combination with Analog output

Hi
I have modified the script thats translate a value in to a static analog output voltage. The value comes from another online running application. The analog output value must remain static until a new value arise. I'm using VB6 and DAQmx 8.5 on a XP computer. The DA converter is NI USB-6211. I have tried to play around with the Start/Stop and clear commands but my script still makes the program highly unstabile.
So am I using the commands correctly?. And have I setup the write commands correctly too. Can anyone allso explain how to use the command Doevent correctly
Dim taskHandle As Long
    Dim clockEdge As Long
    Dim sampsPerCycle As Double
    Dim desiredSampleClockRate As Double
    Dim resultingFrequency As Double
    Dim amplitude As Double
    Dim numSampsPerChannel As Long
    Dim numChannels As Long
    Dim errorCode As Long
    Dim errorString As String
    Dim sampsPerChanWritten As Long
    Dim XICVolt As Double
' Create the DAQmx task.
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    Call DAQmxGetTaskNumChans(taskHandle, numChannels)
    If numChannels > 1 Then
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        errorString = "Please specify only one channel."
        Err.Raise errorCode, , errorString
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Data_is_recorded:
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    GoTo end_script
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    DoEvents
     Call DataPoint.GetDataPoint(thenumberOfDataPoint, theXvalue, theYvalue)
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     lastcycles = theWF.GetActualNumberOfCycles(sampleIndex, 0)
     End If
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end_script:
End If
call DAQmx.stopTask(Taskhandle)
call DAQmx.clearTask(taskhandle)
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David Weber wrote:
thanks lot for all the great feedback. That's really helpful. I think I'll go for the NO_MERGE hint. A first test with this looks good.Keep in mind, only undocumented hint MATERIALIZE along with subquery factoring clause WITH (for which this hint was created) will work in real queries:
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PCI Card for Analog output in the range of 10mv

dear ni,
                I want to know about the PCI card that can be generate analog output in the range of maximum 10mv. i am going to use for caliberation of loadcell, strain gauges devices.
could you tell me on which PCI card will support this type of application.
Regards,
Balaji DP

Try: http://www.ni.com/dataacquisition/
These have analog output voltages < 10V:   http://sine.ni.com/nifn/cds/view/main/p/sn/n12:7604,n3:7853/lang/en/nid/1036/ap/daq
You need something with a high bit count to get good resolution at 10 mV, such as the PCI-6010 which has a 16 bit D/A.
Here are the minimum voltage specs for the 6010:
Minimum Voltage Range
-0.2..0.2 V
      Range Accuracy
283 µV
      Range Sensitivity
6.4 µV
Message Edited by vt92 on 11-18-2009 07:56 AM
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How to building a multi-channels analog output task in visual c++ 6.0 (without Measurement Studio)?

Hello!
I have a PCI 6251 card, and using DAQmx C function to generate a wavwform. (single channel ).
But, how to creating a multi-channels analog output task, and had a different frequence in each channels?
Thanks.

This is getting to be a common question!
The answer is, you can't.
If the rates have common factors, you can use a higher overall rate. The slower waveform will simply have extra points in it to make up for the higher update rate.
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Setting different analog output's parameters in PCI-6229 DAQ card

Hello,
We are using DAQ assistant to set the analog output parameters (frequency).
Is it possible to set different values for each channel using DAQ assistant?
If not using DAQ assistant, what is the other way to set it?
Thank You
Arunas

If you are trying to set different frequencies for waveform generation on two channels, the answer is No, it can't be done. If possible, you will have to pick a sample rate high enough to work for both signals, and use an over-sampled waveform.
Another choice would be to use a second device for the second waveform.
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Using DAQ generate a 38kHz on an analog output on and off for ms using labVIEW

I wish to generate a 38kHz pulse on an analog output of a mydaq to drive a infrared led. The 38kHz signal is not continuous but is on for 1ms and off for 1ms.

Hi pat,
you generate a waveform using 38kHz as sample rate and a rectangular shape of 1ms HIGH level and 1ms LOW level. Using some simple math you will notice you need 38 samples at 38Khz to output a value for 1ms…
Then you just output that waveform on a AO channel.
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How much noise expected in analog output?

I'm using a PCI-MIO-16E-4 with LabView to generate buffered analog output, and at the BNC-2090 output (DAC0/1OUT) I'm finding ~180 Hz hum of about 20 mV peak-to-peak. It doesn't seem to matter whether I'm writing a waveform or not; the noise magnitude is always about the same.
Is there something I can do to eliminate or reduce this, or is it typical so I'm stuck with it? I futzed with the BMC-2090 shield ground jumper (W1) but none of the three documented settings made any difference.
Any suggestions would be greatly appreciated.
thanks,
Kevin

No particular noise is "typical." No noise at all is atypical. 20mV is low enough that it could be radiated noise for nearby equipment. I doubt you card would have that noise in the lab situation where they test for noise. Which essentially means something about you estup is responsible for the noise.
Since the frequency is a multiple of 60Hz it is probably environmental noise, radiated ot picked up off of the ground. Really and truly, 20mV is not a lot. I have acquisitions where I must be very careful in grounding ALL the associated equipment or I see huge blurts of noise from a motor drive - on the order of 3 Volts until I drove an eight foot gound rod through the floor to get an isolated safety ground for my DAQ PC and scope. I still see the noise, but it is now lower than 0.8V so I don't get false triggering of TTL circuitry from it. This is AI not AO like you are discussing.
If you check the specification of your card there is a table on "System noise." I am not saavy enough to understand it, but I see that the noise is dependant on the output range. I suspect that the range is not a user selectable item, but in theory if you see more noise than the spec sheet says, then it is part of your setup not the card.
Here is part you really don't want to hear: Solving a noise problem by text messaging is like solving a mental illness over the phone, maybe worse. I can tell you all sorts of practical, common sense things that are not specifically helpful. I can tell you from personal experience that you really need to follow all the good practices you can, if you really want to have as high a SN ratio as possible.
Can you set up a single point ground? Can you eliminate all ground loops (shielding only grounded on one end.) I had a stray strand of shielding that brushed against a case that made terrible noise once.
There is a good book called ,"Grounding and Shielding Techniques," by Ralph Morrison from Wiley Inter-Science. There are papers on this in in the tech resources of ni.com. In particular the paper on "Field wiring" is good. Keithley has a good book they will send you for free on low level measurements that is very informative. You have to call them on the phone to get it.

Usb 6009 continuous analog output

Hi
I'm pretty new to Labview, so you may have to bear with me. I have a USB-6009 and I want to generate a continuos analog output voltage. I've got the example you have posted 'Gen Mult Volt Updates-SW Timed_LV7.1 (0 to 4).vi' working and it outputs a continuous sine wave.
In a similar manner I need to generate:
1. Ramp up voltage (and ramp down voltage): starting with a continuos constant voltage, which after a period of time linearly increases to another constant voltage, and which allows me to specify the 3 time intervals and the rate of increase.
2. Pulsations: whereby I can specify the amplitude and time interval of each pulsation
This is so that I can control voltage to a valve which regulates my pipe flow. In the example I have (one stated above), I do not understand specifically:
i. Why I need both a 'Software Loop Time (ms)' as well as 'Timeout'
ii. The 'Sinusoidal Pattern' input which seems to generate data for a sine wave- I can't get a description of that and there are no similar VIs for other waveforms; and what is the function of the two numbers it has?
iv. How do I change amplitude and time period for the wave?
iii. What does 'Index Array' do?
thank you

Hi there,
I'm guessing the VI you are using is the one from this KB:
http://digital.ni.com/public.nsf/allkb/6F2C2B49A89D685C8625711D007BDD64
i. The software timed loop control is to control the rate at which you change the voltage output. The timeout on the DAQmx Write VI is the maximum time in seconds the VI will wait to output a sample (eg. if the write buffer is full, the Write VI will wait for it to become available for 'timeout' seconds before outputting an error).
ii. The sine pattern is just an array constant of doubles that make up the sine wave voltage values, and the for loop adds an offset (of two volts) to every single one of those values. You might want to replace that entire array constant and for loop with a Simulate Signal Express VI (just search for Simulate Sig or look in the Functions >> Input palette) and convert the dynamic data output to an array of doubles. You can configure the type of waveform, amplitude, and time period from that express VI as well.
iii. Refer to previous answer.
iv. Index array returns an element of an array based on the index input. You can turn on the context help and move your mouse over functions to get more help on them.
I hope that helps!
Way S.
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2 analog output channels with different frequencies

Hi,
hope that somebody can help me:
I created two physical tasks, analog output channels.
I should give signals (triangle signals) to a scanner. The problem ist that I need these triangle signals with two different frequencies.
I can create the signal with each of the task, but not together. Can I solve this problem somehow?
Ah, and of course the 2 tasks should start together...
Thanks for your help!!
Telly

You didn't mention the type of device you're using, so I'll assume it's a standard MIO. A typical MIO only has one AO timing engine, so you'll have to create one task for both channels and use a single update rate for the task. You will have to make the output frequencies different by passing different data for both channels.
For example, let's say your update rate is 1KHz. The data for channel 0 is 1000 data points of a single cycle of a triangle wave. The data for channel 1 is 1000 data point of two cycles of a triangle wave. When you run the task, you will get a 1Hz triangle wave on channel 0 and a 2Hz triangle wave on channel 1.
Good luck,
Joe

Is inactive analog output will be at high impedance or cut off state?

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