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An easy library for controlling SCPI instruments

Project description


A simple and robust library making communication with SCPI (Standard Control of Programmbale Instruments) instruments easy. After creating an instrument object that connects to an actual instrument, commands are sent to the instrument using a property-like format. This class is useful for inheritance when creating a controller for a specific instrument. Communication with instruments is done with PyVISA.


SCPI Commands

Generic SCPI commands can be executed by transforming the SCPI code in to attributes via the hierarchy relationship, then calling it. Instrument properties can be queried by passing no arguments to the call. Commands with no arguments are run by passing an empty string to the call.


# import package
import easy_scpi as scpi 

# Connect to an instrument
inst = scpi.SCPI_Instrument( <port> )

# Read the voltage [MEASure:VOLTage:DC?]
# or

# Set the voltage to 1 V [MEASure:VOLTage:DC 1]
inst.measure.voltage.dc( 1 )
# or
inst.source.voltage( '1' )

# Execute a command to take a reading [SYSTem:ZCORrect:ACQuire]
inst.syst.zcor.aqc( '' )


**SCPI_Instrument( <port>, backend = '', resource_params ): Creates an instance of a SCPI instrument. The backend is used to create the VISA Resource Manager. Upon connection, the resource_params are passed to the VISA resource.

connect(): Connects the object instance to the actual instrument on the specified port

disconnect(): Disconnects the instrument from the program, closing the port

write( <msg> ): Sends msg to the instrument

read(): Gets the most recent response from the instrument

query( <msg> ): Sends msg to the instrument and returns its response

reset(): Sets the instrument to its default state

init(): Initializes the instrument for a measurement


backend: Returns teh name of teh VISA backend used. [Read Only]

inst: Returns the resource used by the instance. [Read Only]

port: The communication port.

rid: The resource id associated with the instrument. [Read Only]

resource_params: Returns the resource parameters passed on creation. [Read Only]

timeout: The communication timeout of the instrument. [Read Only]

id: The manufacturer id of the instrument. [Read Only]

value: The current value of the instrument. [Read Only]

connected: Whether the instrument is connected or not. [Read Only]

is_connected: Alias for connected.

Full Example

For use with Tektronix PWS4305

#standard imports
import os
import sys

#SCPI imports
import usb
import visa

# scpi controller
import easy_scpi as scpi

class PowerSupply( ic.Instrument ):

    def __init__( self, timeout = 10, rid = None ):
            port = None, 
            timeout = timeout, 
            read_termination = '\n', 
            write_termination = '\n' 

        # other initialization code...

    #--- public methods ---

    def voltage( self ):
        Returns the voltage setting
        return self.source.volt.level()

    def voltage( self, volts ):
        Sets the voltage of the instrument
        self.source.volt.level( volts )

    def current( self ):
        Returns the current setting in Amps
        return self.source.current.level()

    def current( self, amps ):
        Set the current of the instrument
        self.source.current.level( amps )

    def on( self ):
        Turns the output on
        self.output.state( 'on' )

    def off( self):
        Turns the output off
        self.output.state( 'off' )

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