PyVISA SCPI commands and queries (issue with value update)

问题:

UPDATE: 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...

An example of the commands/queries/replies is posted below..

**I am using PyVisa frontend to communicate with a sensor.

I am having to have to send a command or make a query three times before there is a change in the output..

Do I have to add wait command before proceeding, I thought the SCPI commands are blocking (synchronous so as to speak).. Please let me know if I am doing something awry.. here are a few of my commands:**

    >>> import visa     >>> ins = visa.ResourceManager()     >>> print(ins.list_resources())     ('ASRL1::INSTR', 'ASRL3::INSTR', 'ASRL6::INSTR', 'ASRL10::INSTR')     >>> Energy_sense = ins.open_resource('ASRL6::INSTR')     >>> print(Energy_sense.query('*IDN?'))      Coherent, Inc - EnergyMax USB - V1.2 - Jan 27 2011       >>> Energy_sense.write(":CONF:WAVE 780")      (16, <StatusCode.success: 0>)     >>> print(Energy_sense.query(':CONF:WAVE?'))     780        >>> Energy_sense.write(":SYST:COMM:HAND OFF")      (21, <StatusCode.success: 0>)      >>>       >>> Energy_sense.write(":CONF:MEAS:STAT ON")      (20, <StatusCode.success: 0>)      >>> Energy_sense.write(":CONF:STAT:BSIZ 1000")      (22, <StatusCode.success: 0>)       >>> Energy_sense.query(":CONF:STAT:BSIZ?")       '1000\r\n'       >>> Energy_sense.write(":CONF:STAT:STAR")       (17, <StatusCode.success: 0>)       >>> Energy_sense.query(":READ?")        '3.728E-5,3.150E-5,4.358E-5,2.597E-6\r\n'       >>>        >>> Energy_sense.query(":CONF:STAT:BSIZ?")       '1000\r\n'       >>>        >>> print(Energy_sense.query(':CONF:WAVE?'))       780         >>>  

You can find the rest of the commands in the image.

回答1:

You are correct, VISA commands are blocking so you should not need a wait after a VISA command. Have you set the timeout? Is it too short? Some devices may take longer to respond to commands then others.

import visa self._rm = visa.ResourceManager() self._visa_conn = self._rm.open_resource('GPIB0::%s::INSTR' % instr_addr) self._visa_conn.timeout = 1000 # in milliseconds 

You can remove the '\n' with:

string.rstrip('\n') 

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