Can PCI 4462 gain be changed on the fly in VB 2005 express?

[johnd01]

hI,

My present chanil configuration comes form:
 myTask.AIChannels.CreateVoltageChannel(physicalChannelComboBox.Text, "", _
                 AITerminalConfiguration.Differential, Convert.ToDouble(minimumValueNumeric.Value), _
                Convert.ToDouble(maximumValueNumeric.Value), AIVoltageUnits.Volts)

Where "physicalChannelComboBox.Text" = "Dev1/AI0:3

This creats all the channels at one time but I need to have different Min and Max voltages.

Here is a MAX 4462 configuration.

I am trying to do this configuration in VB

DAQmx] MajorVersion MinorVersion

        8       6       
[DAQmxChannel]          AI.Coupling     AI.Max  AI.MeasType     AI.Min  AI.TermCfg      I.Voltage.Units ChanType        PhysicalChanName        
PPI2/PrimaryVolts       DC              42      Voltage -42             Differential    Volts            Analog         Input   Dev1/ai0        
PPI2/PrimaryCurrent     DC              0.316   Voltage -0.316          Differential    Volts            Analog         Input   Dev1/ai1        
PPI2/SecondaryVolts     DC              31.6    Voltage -31.6           Differential    Volts            Analog         Input   Dev1/ai2        
PPI2/SecondaryCurrent   DC              0.316   Voltage -0.316          Differential    Volts            Analog         Input   Dev1/ai3        
[DAQmxTask]     Channels        SampClk.ActiveEdge      SampClk.Rate    SampClk.Src                     SampQuant.SampMode      SampQuant.SampPerChan   SampTimingType  
                                Rising                  195000          Continuous Samples      2000                            ""                              Sample Clock    
PPI2    PPI2/PrimaryVolts, PPI2/PrimaryCurrent, PPI2/SecondaryVolts, PPI2/SecondaryCurrent
[DAQmxDevice]   BusType DevSerialNum    PCI.BusNum      PCI.DevNum      ProductNum      ProductType     
Dev1                    PCI             0x127B518               0x5             0x6             0x7170  PCI-4462        

I would like to be able to look at data values over time and change the gain/rainge of each channel while still recording data. How can I change the gain on the fly.
 

thanks.
john

[gaving]

Hello again, John!

For your first question you can call CreateVoltageChannel multiple times, giving it a different channel with different Min/Max settings to do what you want.

As far as changing gain on the fly, there is no way through our API to do this "on-the-fly" for DSA products.  You will need to stop the task, reconfigure the min/max (two function calls) by setting the properties AI.Min and AI.Max, and then restart the task.

I'll try to find an example to help in the meantime.

Good luck,


Sincerely,
Gavin Goodrich
Software Engineer
National Instruments

[gaving]

OK, changing the min/max can be done like this
stop the task
myTask.AIChannels.Item(0).Maximum = whatever
myTask.AIChannels.Item(0).Minimum = -whatever


the index "0", I believe, is the index of what order you added channels, so if you call CreateVoltageChannel once with ai0, once with ai1, and once with ai2, you will have Item(0) = ai0, Item(1) = ai1, and so on.

enjoy

Gavin Goodrich
Software Engineer
National Instruments

[johnd01]

Thank you Gaving,

Just to make sure that I understand what you are saying:

 myTask.AIChannels.CreateVoltageChannel(physicalChannelComboBox.Text, "", _
                 AITerminalConfiguration.Differential, Convert.ToDouble(minimumValueNumeric.Value), _
                Convert.ToDouble(maximumValueNumeric.Value), AIVoltageUnits.Volts)

myTask.AIChannels.Item(0).Maximum = 31.6
myTask.AIChannels.Item(0).Minimum = -31.6

myTask.AIChannels.Item(1).Maximum = 0.316
myTask.AIChannels.Item(1).Minimum = -0.316

myTask.AIChannels.Item(2).Maximum = 31.6
myTask.AIChannels.Item(2).Minimum = -31.6

myTask.AIChannels.Item(3).Maximum = 3.16
myTask.AIChannels.Item(3).Minimum = -3.16

 Is that what your are saying?

Thanks again,

John

[gaving · Accepted solution]

Yes, that will work.
Just remember that you can't change AI Min and Max while the task is running.
well...at least you won't see a difference while running

Gavin Goodrich
Software Engineer
National Instruments

[johnd01]

thanks