Question communicate to Agilent 34970A over GPIB

[jbrookley]

Hello everyone,

I am currently designing a calibration system for some equipment and want to be able to create a simple interface (initially) that will read real time samples from the Agilent 34970A (Data Acquisition Unit) and display them in a text box continuously until a separate button is pressed, which would interrupt the process. Here is some of my code:

Private Sub StartSampleButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles StartSampleButton.Click

        ioDmm.WriteString("MEAS:VOLT:DC? AUTO,MAX,(@101)")
        RealTimeSample.Text = ioDmm.ReadNumber

End Sub

When I press the StartSampleButton, it takes a single sample from the 34970A and places the result in the RealTimeSample box (no problems here).

The problem comes in when I want to do multiple samples. I've been trying something along the lines of:

Private Sub StartSampleButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles StartSampleButton.Click

While 1
        ioDmm.WriteString("MEAS:VOLT:DC? AUTO,MAX, (@101)")
        RealTimeSample.Text = ioDmm.ReadNumber
        System.Threading.Thread.Sleep(1000)
End While

End Sub

I was hoping it would continuously sample the data and place it in the box but it takes the samples a second apart each time but never places it in the box. Does anyone have any ideas why that might be? (Might be a hardware issue).

The big problem I'm having though is that, assuming I get the data to sample continuously, I want to make it so clicking the StartSample button should cause the program to read data continuously into the RealTimeSample box until the TakeSample Button is pressed, which stops the sampling and moves the data into the TakenSample box.

This is what I have so far:

Dim Sampled As Integer = 0

Private Sub StartSampleButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles StartSampleButton.Click

        While 1
            If Sampled = 0 Then
                ioDmm.WriteString("MEAS:VOLT:DC? AUTO,MAX, (@101)")
                RealTimeSample.Text = ioDmm.ReadNumber
                System.Threading.Thread.Sleep(1000)
            ElseIf Sampled = 1 Then
                Exit While
            End If
        End While

End Sub

Private Sub TakeSampleButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles TakeSampleButton.Click

        TakenSample.Text = RealTimeSample.Text
        Sampled = 1

End Sub

Can anyone help me figure out how to use the TakeSample button as an interrupt to exit the sampling loop? Thanks!

 

[Devilteck]

Try placing a System.doevents in your loop, as the loop may not have time to update the form instance as the sleep command puts the thread to sleep which is not an update

 

[JohnH]

Use a background thread to do the loop.

 

[Devilteck]

i agree that a background worker/thread would work, but depending on the level of his knowledge on such things, it would dictate which would be easier.