topic Re: CompactDaq AI with Visual Basic .NET in Measurement Studio for .NET Languages

CompactDaq AI with Visual Basic .NET

DieselPower — Thu, 21 Dec 2006 14:31:50 GMT

Does anyone have any code for doing analog input with CompactDAQ and VB.NET? My SCXI code is returning ~-250 C on thermocouple readings. If I reset the chassis with MAX and then read with MAX, I get normal readings. If I try to run VB it won't work in either until I reset the chassis in MAX again.

This is the code I am using:

[vb]
            While ChannelCount < numChannels
                While AIChannels(ChannelCount).Device = Device
                    TasksChannelCount(TaskCount) += 1

                    With AIChannels(ChannelCount)
                        Select Case AIChannels(ChannelCount).Type
                            Case Is = "Temperature"
                                Tasks(TaskCount).AIChannels.CreateThermocoupleChannel(.Device & "/" & _
                                                .Channel, Trim(.Name), .Min, .Max, AIThermocoupleType.K, _
                                                AITemperatureUnits.DegreesC)
                                If Not .Device.Contains("cDAQ") Then
                                    Tasks(TaskCount).AIChannels(.Name).AutoZeroMode = AIAutoZeroMode.None
                                    Tasks(TaskCount).AIChannels(.Name).LowpassEnable = True
                                    Tasks(TaskCount).AIChannels(.Name).LowpassCutoffFrequency = 4
                                End If
                            Case Is = "Voltage"
                                Tasks(TaskCount).AIChannels.CreateVoltageChannel(.Device & "/" & .Channel, _
                                                .Name, AITerminalConfiguration.Differential, _
                                                .Min, .Max, AIVoltageUnits.Volts)
                                If Not .Device.Contains("cDAQ") Then
                                    Tasks(TaskCount).AIChannels(.Name).AutoZeroMode = AIAutoZeroMode.None
                                    Tasks(TaskCount).AIChannels(.Name).LowpassEnable = True
                                    Tasks(TaskCount).AIChannels(.Name).LowpassCutoffFrequency = 4
                                End If
                            Case Else
                                MsgBox("Error in channel configuration!", MsgBoxStyle.Critical, "Warning!")
                                frmD.txtMessage.Text = "Error in Channel Configuration. Abort." & vbNewLine _
                                                        & frmD.txtMessage.Text
                                Exit Sub
                        End Select
                    End With
                    ChannelCount += 1

                End While

                Tasks(TaskCount).Timing.ConfigureSampleClock("", SampleRate, SampleClockActiveEdge.Rising, _
                                                             SampleQuantityMode.FiniteSamples, numSamples)
                Tasks(TaskCount).Control(TaskAction.Verify)
                Tasks(TaskCount).Control(TaskAction.Unreserve)

                reader(TaskCount) = New AnalogMultiChannelReader(Tasks(TaskCount).Stream)

                TaskCount += 1
                TasksChannelCount(TaskCount) = 0
                Device = AIChannels(ChannelCount).Device
            End While
[/vb]

Re: CompactDaq AI with Visual Basic .NET

DieselPower — Thu, 21 Dec 2006 21:53:32 GMT

OK, I got it to read now, but I am having some speed issues. It works very well using only one NI 9211. On my SCXI applications I create one task per module, but that approach had problems on Compact DAQ. I changed it to one task per chassis, and it is horribly slow now I NEED to have these things update a chassis full of TC readings at 1 Hz (with some cushion time).

What is the best approach for reading 8 modules full of TC readings on these 9211s?
Why are they so slow? (14 S/s)

Re: CompactDaq AI with Visual Basic .NET

Neil_S. — Fri, 22 Dec 2006 17:04:32 GMT

Thanks for posting to the NI forums. What rate are you specifying for the acquisition? Are you able to achieve 14 S/s on a single channel or only read 14 channels in a second? If you increase the sampling rate do you get an error? You should be able to achieve your desired sample rate of 1 Hz. Actually, if you scan at a higher rate the driver should still let you do so but samples will be repeated due to the long settling time of the 9211. You should be able to scan at around 6 Hz without any repeated data. Let me know if this does not resolved the issue. Good luck with your application and have a happy holiday season.

Regards,

Neil S.
Applications Engineer
National Instruments

Re: CompactDaq AI with Visual Basic .NET

DieselPower — Fri, 22 Dec 2006 17:11:35 GMT

I do not get errors when I request higher acquisition rates like I would for an E-series card. I have requested rates from 14 to 500 and I still have trouble. When I do one task per module, the first module behaves very oddly (every 5 or so seconds it reads correctly, but the other 4 readings are bad and it repeats the same pattern). When I do one task per chassis (1 chassis currently), I get no value for the first channel and my loop time is 3-4 seconds. Will a single chassis return 2 real readings per second from 32 total channels? Has anyone at NI tested these units using Measurement Studio and VB.NET? Are there any plans for faster TC modules?

I think that I will write a program today to take one reading and throw all of the data into a table so I can set what it is returning and how long it is taking.

Thanks.

Re: CompactDaq AI with Visual Basic .NET

Neil_S. — Fri, 22 Dec 2006 17:49:34 GMT

Michael,

The behavior you are seeing does seem odd indeed. How many samples per channel are you acquiring on each iteration of the loop? Could you post the code that you have contained in your loop?

Thanks,

Neil S.
Applications Engineer
National Instruments

Re: CompactDaq AI with Visual Basic .NET

DieselPower — Fri, 22 Dec 2006 18:34:54 GMT

        For TaskCount = 0 To NumberOfModules - 1
            Tasks(TaskCount) = New Task("mod" & Trim(Str(TaskCount + 1)) & "task")
        Next

        Device = AIChannels(0).Device

        Try
            While ChannelCount < numChannels
                While AIChannels(ChannelCount).Device = Device
                    TasksChannelCount(TaskCount) += 1

                    With AIChannels(ChannelCount)
                        Select Case AIChannels(ChannelCount).Type
                            Case Is = "Temperature"
                                Tasks(TaskCount).AIChannels.CreateThermocoupleChannel(.Device & "/" & _
                                                .Channel, Trim(.Name), .Min, .Max, AIThermocoupleType.K, _
                                                AITemperatureUnits.DegreesC)
                                If Not .Device.Contains("cDAQ") Then
                                    Tasks(TaskCount).AIChannels(.Name).AutoZeroMode = AIAutoZeroMode.None
                                    Tasks(TaskCount).AIChannels(.Name).LowpassEnable = True
                                    Tasks(TaskCount).AIChannels(.Name).LowpassCutoffFrequency = 4
                                End If
                            Case Is = "Voltage"
                                Tasks(TaskCount).AIChannels.CreateVoltageChannel(.Device & "/" & .Channel, _
                                                .Name, AITerminalConfiguration.Differential, _
                                                .Min, .Max, AIVoltageUnits.Volts)
                                If Not .Device.Contains("cDAQ") Then
                                    Tasks(TaskCount).AIChannels(.Name).AutoZeroMode = AIAutoZeroMode.None
                                    Tasks(TaskCount).AIChannels(.Name).LowpassEnable = True
                                    Tasks(TaskCount).AIChannels(.Name).LowpassCutoffFrequency = 4
                                End If
                            Case Else
                                Removed to fit post
                                Exit Sub
                        End Select
                    End With
                    ChannelCount += 1
                    If ChannelCount = numChannels Then Exit While
                    If AIChannels(0).Device.Contains("cDAQ") Then
                        Device = AIChannels(ChannelCount).Device
                    End If
                End While

                Tasks(TaskCount).Timing.ConfigureSampleClock("", SampleRate, SampleClockActiveEdge.Rising, _
                                                             SampleQuantityMode.FiniteSamples, numSamples)
                Tasks(TaskCount).Control(TaskAction.Verify)
                Tasks(TaskCount).Control(TaskAction.Unreserve)

                reader(TaskCount) = New AnalogMultiChannelReader(Tasks(TaskCount).Stream)

                TaskCount += 1
                TasksChannelCount(TaskCount) = 0
                Device = AIChannels(ChannelCount).Device
            End While

Message Edited by SCXI and MS 2k3-VB.NET on 12-22-2006 12:44 PM

Re: CompactDaq AI with Visual Basic .NET

DieselPower — Fri, 22 Dec 2006 18:35:31 GMT

Reading the data

                g = h = i = 0

                For Count = 0 To NumberOfModules - 1
                    Task1Data = reader(Count).ReadMultiSample(numSamples)
                    For h = i To i + TasksChannelCount(Count) - 1
                        sum(h) = 0
                    Next

                    For h = i To i + TasksChannelCount(Count) - 1
                        For g = 0 To numSamples - 1
                            sum(h) = sum(h) + Task1Data(h - i, g)
                        Next
                    Next

                    i = h
                Next

                For h = 0 To numChannels
                    With AIChannels(h)
                        average(h) = sum(h) / numSamples
                        value(h) = average(h) ^ 4 * .Quartic + _
                                   average(h) ^ 3 * .Cubic + _
                                   average(h) ^ 2 * .Quadratic + _
                                   average(h) * .Linear + _
                                   .Offset
                    End With
                Next

Re: CompactDaq AI with Visual Basic .NET

Erik_J — Wed, 27 Dec 2006 21:29:43 GMT

Hi Michael,

You are experiencing very odd behavior and from looking at your code here, it has been difficult for us to determine what is wrong. One suggestion I have is to use one task contianing your 8 thermocouple channels across the 8 devices instead of having 8 tasks each with one device, this may speed things up.

Also, did you have a chance to write a program to take one reading and throw all of the data into a table so we can see what it is returning and how long it is taking?

We have a shipping example located in the C:\Program Files\National Instruments\MeasurementStudioVS2005\DotNET\Examples\DAQmx\Analog In\Measure Temperature\ContAcqThermocoupleSamples_IntClk\Vb folder. This example has been tested and should work with the 9211 in reading Thermocouple channels. Please take a look at it if you have not already.

If you are still having trouble getting the thermocouples to read properly, could you please attach all of your code, preferably in a .zip file contianing the project file and source files so we can run the code on our end?

Thanks for your patience Michael, I hope you are enjoying the holidays!

Regards,
Erik J.
Applications Engineer
National Instruments

Re: CompactDaq AI with Visual Basic .NET

DieselPower — Wed, 27 Dec 2006 21:49:46 GMT

I will write the program to take readings and put them in a table tomorrow and after making a test run I will report back with my results.

Re: CompactDaq AI with Visual Basic .NET

Erik_J — Thu, 28 Dec 2006 15:48:14 GMT

Great! Thanks Michael. Your results should be interesting. If you still have a 9211 speed issue after running your program, please post it you code so we can reproduce the results on our end.

Regards,
Erik J.

Re: CompactDaq AI with Visual Basic .NET

DieselPower — Thu, 28 Dec 2006 22:09:12 GMT

Well, I can run at 1 sample per channel, but nothing more. Any more than 1 makes 1<loop time<2. I run a thread and I don't think the thread finishes before the next thread is called and then my loop times just get greater and greater even though the loop is still executing. The following chart details the data I have obtained:

File   Samples/Channel   SampleRate
3         2                              14
4         1                            14
5         2                              100
6         1                            100
7         1                            200

Files and project attached.

Re: CompactDaq AI with Visual Basic .NET

DieselPower — Thu, 28 Dec 2006 22:10:48 GMT

The actual time is listed on the right hand column. The second from the right is s:ms

Re: CompactDaq AI with Visual Basic .NET

DieselPower — Thu, 28 Dec 2006 22:52:59 GMT

I just ran a comparison between a CompactDAQ chassis full of thermocouples (same as the other files) reading during a test. The channels only update every other second, which means our charts look like stair cases and it could be a 100 degree difference from one second to the next in some cases. This is not acceptable. We have to figure this out.

I was running at 1 S/channel, 1 task for the entire chassis, and 200 S/s rate.

Loop time was set to 1000 ms using a timer that calls a thread set to highest priority.

The program screen shot was from run 6. the chart screen shot was from the actual test data.

Message Edited by SCXI and MS 2k3-VB.NET on 12-28-2006 04:55 PM

Message Edited by SCXI and MS 2k3-VB.NET on 12-28-2006 04:56 PM

Re: CompactDaq AI with Visual Basic .NET

Erik_J — Fri, 29 Dec 2006 19:58:55 GMT

Hi Michael,

We are having difficulting running and debugging your code, primarily due to the heavy Excel involvement. I believe that the best thing to do is for you to trim the code down as much as possible. Ideally, having code that simply reads from all the channels and stores the values in arrays (time vs temperature). This way, we isolate the problem and it will be much easier for us to determine what is wrong.

Thank you,
Erik

Re: CompactDaq AI with Visual Basic .NET

DieselPower — Fri, 29 Dec 2006 20:08:31 GMT

In order to run the code, you must have a folder in the application startup path called "Data", and a folder called "Lookup Tables" with a subfolder inside that called "Tables." Inside of the tables folder you should have Channel Configuration.xls. Are you guys using Office 2003? I've attached screen shots of the directorty trees..

Re: CompactDaq AI with Visual Basic .NET

DieselPower — Fri, 29 Dec 2006 20:12:24 GMT

Try this zip file. The other one is lacking pretty much everything. 😉

Re: CompactDaq AI with Visual Basic .NET

Erik_J — Tue, 02 Jan 2007 15:31:32 GMT

Good Morning Michael,

We are still experiencing an error when trying to build your code: Excel.Application, Excel.Workbook, and Excel.Worksheet are undefined. Any ideas?

Thanks!
Erik

Re: CompactDaq AI with Visual Basic .NET

KyleBryson — Tue, 02 Jan 2007 16:11:26 GMT

Michael, all,

I'm no VB expert, but here a couple of notes on the hardware that may be useful.

The 9211 is multiplexed and scans channels at 14 S/s. If autozero is used (looks like you aren't) or the CJC is read, those count as channels. So one channel w/o CJC can go 14 S/s, one w/ CJC can go 7 S/s, four w/o CJC 3.5 S/s, and four channels w/ CJC can go 2.8 S/s. The hardware was designed to be very accurate, but not very fast, since temperature does not usually change quickly. It sounds like your goal is a system with all channels sampling once per second, which should be doable under any hardware settings.

A cDAQ chassis can only execute one AI task at a time. If you use a task per module, you will have to stop each task and start the next one in sequence, which will be quite slow, because module one's task will take at least 280 ms, followed by module two, etc., for far worse than an aggregate 1 Hz rate.

Actually, I wonder if this could be the problem. Are you executing a single task for the entire chassis for a finite number of samples, or stopping and restarting the task every time through the loop? Starting and stopping the task can have significant overhead, and can include acquisition of a sample, so you don't want that in your loop. Make sure to start the task outside of your loop, read samples in the loop, and then stop the task outside the loop after it completes. If you do this with a single task w/ 32 channels (or 40, w/ CJCs), the chassis should simultaneously acquire data on all 8 modules, and perform at or very near 3.5 S/s.

The reason the 9211 can return repeated data (unlike your E Series) is for compatibility with the much faster modules (> 100 kS/s) available in the platform. I realize this can be confusing, but in your case (9211 only), you should be able to set sample rates in the neighborhood of 1-3 Hz and never see the repeated data.

That's one other thing--make sure you're controlling sample clock rates, not convert rate parameters that may have applied to an SCXI-based system. CompactDAQ doesn't use a single multiplexed ADC to scan channels like an E Series or M Series connected to an SCXI chassis, and there is no chassis convert clock.

Good luck, and keep posting questions until we get things working.

Regards,
Kyle

Re: CompactDaq AI with Visual Basic .NET

DieselPower — Tue, 02 Jan 2007 16:14:54 GMT

Are you getting a blue underlined error everywhere that "Excel" is reference? It may have to do with the fact that your .ddls are in a different location than mine. I had this problem also, and was instructed to go to the projet dependencies through the project explorer tree and refreshing or searching for the correct location.

Try going to project properties and looking at your references. Remove the reference and then grab your microsoft excel object library 11.0.

"Open up solution explorer and expand your references.

Then right-click on the 'Excel' reference and choose 'Properties...'.

Then look at the 'Path' property. I think you'll find that your reference is local to your '/bin' folders. This means that you are using a local interop assembly (local IA) instead of the Primary Interop Assembly (PIA) for Excel 2003.

Excel 2003 generally will have the PIA's installed automatically, but if the Excel version is not a full install, then they will not be there. The solution is to got to the Constrol Panel > Add Remove Programs... and then find Excel or Office 2003. Finish the installation."

See this thread for details: http://www.xtremevbtalk.com/showthread.php?t=276739

Re: CompactDaq AI with Visual Basic .NET

DieselPower — Tue, 02 Jan 2007 16:32:06 GMT

Kyle,

I am using only one task for the entire chassis. I started out trying to use my SCXI code which creates a new task for each module, but quickly found that it would not work well.

Should I refrain from referencing the CJC? Will that negatively effect the quality of my data?

I create the task when the program begins, and then call the reader object to readmultisamples within the loop.

At certain points in our test, temperature increases at up to 100 C/s. This is why 1 Hz data is so important.

Thank you for all the information!

Message Edited by SCXI and MS 2k3-VB.NET on 01-02-2007 10:33 AM