title: PyVISA SCPI commands and queries (issue with value update)
body: <p>UPDATE: It seems to be working "OK" this am... although I am not sure why certain replies have /r/n at the end and why certain don't. I have explicitly turned Handshaking OFF...</p>
  
  <p>An example of the commands, queries, and replies is posted below.</p>
  
  <p><img src="https://i.stack.imgur.com/bZqKY.png" alt="PyVISA SCPI command output"></p>
  
  <p>**I am using PyVISA frontend to communicate with a sensor.</p>
  
  <p>I am having to have to send a command or make a query three times before there is a change in the output...</p>
  
  <p>Do I have to add wait command before proceeding? I thought the SCPI commands were blocking (synchronous so as to speak). Please let me know if I am doing something awry. Here are a few of my commands:**</p>
  
  <pre><code>    &gt;&gt;&gt; import visa
      &gt;&gt;&gt; ins = visa.ResourceManager()
      &gt;&gt;&gt; print(ins.list_resources())
      ('ASRL1::INSTR', 'ASRL3::INSTR', 'ASRL6::INSTR', 'ASRL10::INSTR')
      &gt;&gt;&gt; Energy_sense = ins.open_resource('ASRL6::INSTR')
      &gt;&gt;&gt; print(Energy_sense.query('*IDN?'))
       Coherent, Inc - EnergyMax USB - V1.2 - Jan 27 2011
  
  
      &gt;&gt;&gt; Energy_sense.write(":CONF:WAVE 780")
       (16, &lt;StatusCode.success: 0&gt;)
      &gt;&gt;&gt; print(Energy_sense.query(':CONF:WAVE?'))
      780
  
  
       &gt;&gt;&gt; Energy_sense.write(":SYST:COMM:HAND OFF")
       (21, &lt;StatusCode.success: 0&gt;)
       &gt;&gt;&gt;
       &gt;&gt;&gt; Energy_sense.write(":CONF:MEAS:STAT ON")
       (20, &lt;StatusCode.success: 0&gt;)
       &gt;&gt;&gt; Energy_sense.write(":CONF:STAT:BSIZ 1000")
       (22, &lt;StatusCode.success: 0&gt;)
        &gt;&gt;&gt; Energy_sense.query(":CONF:STAT:BSIZ?")
        '1000\r\n'
        &gt;&gt;&gt; Energy_sense.write(":CONF:STAT:STAR")
        (17, &lt;StatusCode.success: 0&gt;)
        &gt;&gt;&gt; Energy_sense.query(":READ?")
         '3.728E-5,3.150E-5,4.358E-5,2.597E-6\r\n'
        &gt;&gt;&gt;
        &gt;&gt;&gt; Energy_sense.query(":CONF:STAT:BSIZ?")
        '1000\r\n'
        &gt;&gt;&gt;
        &gt;&gt;&gt; print(Energy_sense.query(':CONF:WAVE?'))
        780
  
        &gt;&gt;&gt;
  </code></pre>
  
  <p>You can find the rest of the commands in the image.</p>