API Reference
Explore the PyVISA API to manage and interact with instruments via VISA standards.
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")Resource Manager
The ResourceManager handles VISA resources and manages sessions.
Methods
| Method | Description | Returns |
|---|---|---|
list_resources(query?) | Returns all available VISA resources | tuple[str] |
open_resource(resource, **kwargs) | Opens connection to an instrument | Instrument |
close() | Closes the Resource Manager session | None |
Example:
import pyvisa
rm = pyvisa.ResourceManager()
resources = rm.list_resources()
instrument = rm.open_resource(resources[0])
instrument.close()Instrument
The Instrument class sends and receives commands from measurement devices.
Methods
| Method | Description | Returns |
|---|---|---|
query(command) | Sends command and reads response | str |
write(command) | Sends command to instrument | int (bytes written) |
read() | Reads data from instrument | str |
clear() | Clears instrument state and buffers | None |
Attributes
| Attribute | Description | Type | Default |
|---|---|---|---|
timeout | Timeout for operations (milliseconds) | int | 2000 |
write_termination | Characters appended to writes | str | None |
read_termination | Expected termination characters | str | None |
baud_rate | Serial baud rate | int | 9600 |
query_delay | Delay between write/read (seconds) | float | 0.0 |
parity | Serial parity setting | Parity | Parity.none |
stop_bits | Serial stop bits | StopBits | StopBits.one |
data_bits | Serial data bits | int | 8 |
chunk_size | Buffer size (bytes) | int | 20480 |
Example:
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)Exception Handling
PyVISA raises exceptions for error handling during instrument communication.
Exceptions
| Exception | Description | When Raised |
|---|---|---|
VisaIOError | VISA I/O operation failure | Communication errors |
InvalidSession | Invalid or closed session | Using closed instruments |
InvalidResource | Invalid resource string | Malformed VISA addresses |
TimeoutError | Operation timeout | Exceeding timeout period |
Example:
try:
instrument.write('*IDN?')
response = instrument.read()
except pyvisa.VisaIOError as e:
print(f"Error: {e}")How is this guide?
