[COM] Communication issue with Agilent 33250A using pyvisa

I am using pyvisa to connect to 33250A, however it works not well. The code shown below worked well for Agilent 2700.

import pyvisa
rm = pyvisa.ResourceManager()
print(rm.list_resources())
inst = rm.open_resource(u'GPIB0::10::INSTR')
print(inst.query("*IDN?"))

The error is occurred line 4 ,

rm.open_resource(u'GPIB0::10::INSTR')

The detail is shown below,

Traceback (most recent call last):
  File "C:/Users/56942/PycharmProjects/NI-instruments/main.py", line 4, in <module>
    inst = rm.open_resource(u'GPIB0::10::INSTR')
  File "C:\Users\56942\PycharmProjects\NI-instruments\venv\lib\site-packages\pyvisa\highlevel.py", line 3271, in open_resource
    info = self.resource_info(resource_name, extended=True)
  File "C:\Users\56942\PycharmProjects\NI-instruments\venv\lib\site-packages\pyvisa\highlevel.py", line 3197, in resource_info
    ret, err = self.visalib.parse_resource_extended(self.session, resource_name)
  File "C:\Users\56942\PycharmProjects\NI-instruments\venv\lib\site-packages\pyvisa\ctwrapper\functions.py", line 2089, in parse_resource_extended
    for val in (resource_class, unaliased_expanded_resource_name, alias_if_exists)
  File "C:\Users\56942\PycharmProjects\NI-instruments\venv\lib\site-packages\pyvisa\ctwrapper\functions.py", line 2089, in <listcomp>
    for val in (resource_class, unaliased_expanded_resource_name, alias_if_exists)
  File "C:\Users\56942\PycharmProjects\NI-instruments\venv\lib\site-packages\pyvisa\ctwrapper\types.py", line 74, in buffer_to_text
    return buf.value.decode("ascii")
    
UnicodeDecodeError: 'ascii' codec can't decode byte 0xe6 in position 0: ordinal not in range(128)
('GPIB0::10::INSTR',)

Process finished with exit code 1

and it works well by using connect expert

Output of pyvisa-info

Machine Details:

Platform ID: Windows-10-1909 Processor: Intel® Core™ i5-4200M CPU @2.5GHz 2.49GHz

Python:

Interpreter: Python 3.7.3 PyVISA Version: 1.11.3 NI version: NI-488.2 18.5

[MatthieuDartiailh]

I assume you are using a Keysight USB to GPIB adapter. This kind of adapter can only be used in conjunction with the adapter manufacturer VISA implementation. You could also try to use the Keysight VISA conflict manager (In connection expert look under Tools, and specify to use Keysight VISA for GPIB resources, it may solve your issue without having to explicitly pass the path to the dll.

[HaoLiuwide]

Thank you for your advice. The problem is related to the two type of VISA. I solved the problem by

import pyvisa as visa

# rm = visa.ResourceManager()
rm = visa.ResourceManager('C:/Program Files (x86)/IVI Foundation/VISA/WinNT/agvisa/agbin/visa32.dll')

print(rm.list_resources())
my_2612A = rm.open_resource('GPIB0::10::INSTR')  
print(my_2612A.query('*IDN?'))

Although the problem was solved, I have some questions. If I have only NI-VISA installed, my computer could not recognize GPIB devices in the Measurement & Automation Explorer. Only if both NI-VISA and Keysight VISA were installed, my computer worked well.