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33220A software trigger

Question asked by karahan on Nov 8, 2019
Latest reply on Nov 9, 2019 by Tardz

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Hi,
I am using 33220A signal generator. I want to start a waveform simultaneously at 2 different signal generators. To do this, I first create a waveform and upload it, activate burst mode, set cycle number to infinity and adjust other parameters for both devices. I am doing all of these with PyVisa library. After that, I set one device to BUS trigger mode and other to EXT trigger mode. I also connected 10 MHz out of one device to 10 MHz in of other device along with trigger ports. However, when I trigger first device with BUS trigger command, second one is not triggered infinitely. I suspect that BUS trigger does not generate required trigger waveform. I would be pleased if you can help me clarifying this issue.
Best regards
Emir Ali Karahan

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Tardz Nov 8, 2019 9:50 PM
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Hi, If I understand you want to start two generator, one with BUS trigger and other with EXTERNAL Trigger; if you start first generator with BUS trigger, the second will not start because it use the EXT Trigger mode. Generator use only one mode at time.

You choose IMM, EXT or BUS.

Simply use same signal on Trig EXT connectors for both generator and use EXT mode Trigger source.

Yves
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- karahan @ Tardz on Nov 9, 2019 10:05 AM
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  I want to start them simultaneously and if possible programatically. Does BUS trigger generate a trigger sequence at EXT TRIG port?
  This was described here (How to synchronize multiple function/arb waveform generators ) with manual trigger, however, I do not prefer it.
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Tardz Nov 9, 2019 2:01 PM
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   Ok, you must use GET command to do TRIG on several instruments. I've done a little vb.net program to test this functionnality...sorry not in PyVisa.

I tested this code with success on my 2 generators: 33220A and 33120A (I don't have two 33220A). I had some delay between generator (few µs), probably because the 2 generators are not synchronized on the same source ... the 33120A does not have this option.

Hoping that this information can help you.

Yves

Dim I As Integer
Dim nb_Instrument As Integer = 2 '2 for two generators
Dim gpib_address() As String
Dim GENERATOR() As Long
Dim actual As Long
Dim defaultRM As Long
Dim GPIBcommand As String
---------------------------------------------------
Private Sub MainForm_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
      initGPIB()
      VISA_GET()
End Sub
---------------------------------------------------
Sub initGPIB()

      ReDim gpib_address(0 To nb_Instrument)

      'Set the address of the interface (acts as the controller)
      gpib_address(0) = "GPIB0::INTFC" 'need to do multiple instruments trigger

      'Set the addresses of the two units
      gpib_address(1) = "GPIB0::10::INSTR" '33220a generator #1
      gpib_address(2) = "GPIB0::13::INSTR" '33220a generator #2

      'Redimension GENERATOR()
      ReDim GENERATOR(0 To nb_Instrument)'redim for nb of instruments to be trigged

      'Initialize VISA system
      visa32.viOpenDefaultRM(defaultRM)

      'Connect to instruments
    For I = 0 To nb_Instrument
            'Open a session to a specified device
            visa32.viOpen(defaultRM, gpib_address(I), VI_NULL, 1000, GENERATOR(I))
      Next

End Sub
---------------------------------------------------

Sub VISA_GET()

     'Set source to BUS
      For I = 1 To nb_Instrument
            GPIBcommand = "TRIG:SOUR BUS" & vbLf
            visa32.viGpibCommand(GENERATOR(I), GPIBcommand, Len(GPIBcommand), actual)
      Next

     'Delay between initiate and triggering
      System.Threading.Thread.Sleep(500) '0.5s

      'Make instruments listen and computer interface talk
      GPIBcommand = "?U!-*" 'CHAR - is for ADDRESS 13, AND * FOR 10 see chart above
      visa32.viGpibCommand(GENERATOR(0), GPIBcommand, Len(GPIBcommand), actual)

      'GET
      visa32.viAssertTrigger(GENERATOR(0), VI_TRIG_PROT_DEFAULT)

      LOCALmode()

End Sub
---------------------------------------------------
Private Sub LOCALmode()
      'Send Instruments to Local
      For I = 1 To nb_Instrument
      visa32.viGpibControlREN(GENERATOR(I), visa32.VI_GPIB_REN_ADDRESS_GTL)
      Next
End Sub
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- karahan @ Tardz on Nov 9, 2019 2:17 PM
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  Thanks for your reply. I have a couple of questions
  "I had some delay between generator (few µs), probably because the 2 generators are not synchronized on the same source ... the 33120A does not have this option."
  Does this mean that you cannot connect 10 MHz reference clock ports together?
  Also, let us assume that I did that connection between two 33220A. In this case will I still observe a delay?
  Best,
  Emir
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  - Tardz @ karahan on Nov 9, 2019 9:59 PM
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    Hi,
    
    It is not possible to connect a 10MHz reference to the 33120A. This will cause a little delay, but my problem is rather the delay of propagation between the receipt of the command and its measurable output. These are two different instruments model, so not identical execution times. In your case, it will be 2 identical devices, this error delay will be much lower, but not null, there are no SYNC between generator to synchronise outputs, only GPIB command.
    
    I tested my 2 generators with external TRIG, the delay error was 10µs, and 300µs for TRIG BUS.
    
    I you need more timing precision, look for two channels generator, the skew between channels will be very low.
    True Series Waveform generators
    
    Yves
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33220A software trigger

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