PyVISA API Reference

Control measurement instruments using the VISA standard with the PyVISA library.

import pyvisa

pyvisa.log_to_screen()
rm = pyvisa.ResourceManager()

instruments = rm.list_resources()

# Using "with" closes the instrument properly even if an exception occurs
with rm.open_resource(instruments[-1]) as inst:
  # Common for serial instruments
  inst.write_termination, inst.read_termination = '\n', '\r\n'

  # Identify the instrument (manufacturer, model, serial number, firmware version)
  idn_response = inst.query('*IDN?')
  print(f"Instrument ID: {idn_response}")
  
  # Set voltage to 12V
  inst.write("VOLT 12")
  print(f"Voltage Set: {inst.query('VOLT?')}V")

Class

Resource Manager

The ResourceManager handles VISA resources and manages sessions.

Name
list_resources
Type
method
Description
Returns a list of available VISA resources.
Name
open_resource
Type
method
Description
Opens a connection to a VISA instrument.
Name
close
Type
method
Description
Closes the Resource Manager session.

import pyvisa
rm = pyvisa.ResourceManager()
resources = rm.list_resources()
instrument = rm.open_resource(resources[0])
instrument.close()

Class

Instrument

The Instrument class sends and receives commands from measurement devices.

Name
query
Type
method
Description
Sends a command and reads the response.
Name
write
Type
method
Description
Sends a command to the instrument.
Name
read
Type
method
Description
Reads data from the instrument.
Name
clear
Type
method
Description
Clears the instrument state.
Name
timeout
Type
attribute
Description
Timeout for read/write operations in milliseconds.
Name
write_termination
Type
attribute
Description
Character(s) appended to each write operation.
Name
read_termination
Type
attribute
Description
Character(s) expected at the end of a read operation.
Name
baud_rate
Type
attribute
Description
Baud rate for serial communication.
Name
query_delay
Type
attribute
Description
Delay between write and read in query operations (seconds).
Name
parity
Type
attribute
Description
Parity setting for serial communication.
Name
stop_bits
Type
attribute
Description
Stop bits for serial communication.
Name
data_bits
Type
attribute
Description
Data bits for serial communication.
Name
chunk_size
Type
attribute
Description
Buffer size for data transfers (bytes).

inst.timeout = 2000  # Timeout in milliseconds
inst.write_termination = '\n'
inst.read_termination = '\r\n'
inst.chunk_size = 20480  # Default chunk size

instrument.query('*IDN?')
instrument.write('VOLT 12')
response = instrument.read()
print(response)

Exceptions

Exception Handling

PyVISA raises exceptions for error handling during instrument communication.

Name
VisaIOError
Type
exception
Description
Raised for VISA I/O operation failures.
Name
InvalidSession
Type
exception
Description
Raised when accessing an invalid session.

try:
  instrument.write('*IDN?')
  response = instrument.read()
except pyvisa.VisaIOError as e:
  print(f"Error: {e}")