The
Standard Commands for Programmable Instruments (SCPI) (often pronounced "skippy") defines a standard set of commands to control programmable test and measurement devices in
instrumentationInstrumentation is the branch of engineering that deals with measurement and control.According to ISA or known as Instrumentation and Systems Automation Society formerly known as Instrument Society of America, the official definition of Instrumentation - is a collection of Instruments and their...
systems.
The SCPI Standard specifies the
syntaxIn linguistics, syntax is the study of the principles and rules for constructing sentences in natural languages...
the command structure, and data formats for programmable instrument control. The physical communications link, such as
GPIB (IEEE-488) IEEE-488 is a short-range, digital communications bus specification that has been in use for over 30 years. Originally created for use with automated test equipment, the standard is still in wide use for that purpose...
, RS232, USB, VXIbus etc, is notdefined by SCPI.
The
Standard Commands for Programmable Instruments (SCPI) (often pronounced "skippy") defines a standard set of commands to control programmable test and measurement devices in
instrumentationInstrumentation is the branch of engineering that deals with measurement and control.According to ISA or known as Instrumentation and Systems Automation Society formerly known as Instrument Society of America, the official definition of Instrumentation - is a collection of Instruments and their...
systems.
The SCPI Standard specifies the
syntaxIn linguistics, syntax is the study of the principles and rules for constructing sentences in natural languages...
the command structure, and data formats for programmable instrument control. The physical communications link, such as
GPIB (IEEE-488) IEEE-488 is a short-range, digital communications bus specification that has been in use for over 30 years. Originally created for use with automated test equipment, the standard is still in wide use for that purpose...
, RS232, USB, VXIbus etc, is notdefined by SCPI. SCPI also includes standard command sets for several classes of instruments, e.g.
power suppliesPower supply is a reference to a source of electrical power. A device or system that supplies electrical or other types of energy to an output load or group of loads is called a power supply unit or PSU...
, loads, and measurement devices such as
voltmeterA voltmeter is an instrument used for measuring the electrical potential difference between two points in an electric circuit. Analog voltmeters move a pointer across a scale in proportion to the voltage of the circuit; digital voltmeters give a numerical display of voltage by use of an analog to...
s and oscilloscopes. A predecessor of SCPI, but with more limited scope, was
IEEE 488.2IEEE-488 is a short-range, digital communications bus specification that has been in use for over 30 years. Originally created for use with automated test equipment, the standard is still in wide use for that purpose...
in 1987.
SCPI commands are
ASCIIThe American Standard Code for Information Interchange is a character-encoding scheme based on the ordering of the English alphabet. ASCII codes represent text in computers, communications equipment, and other devices that use text...
textual strings, which are sent to the instrument over the physical layer, such as GPIB. Responses to query commands are typically ASCII strings, too. However, for bulk data, such as acquired signal data, binary formats can be used.
Two examples: With the command
SYSTem:COMMunicate:SERial:BAUD 2400 the
baudrateIn telecommunications and electronics, baud is synonymous to symbols per second or pulses per second. It is the unit of symbol rate, also known as baud rate or modulation rate; the number of distinct symbol changes made to the transmission medium per second in a digitally modulated signal or a...
of an RS232 interface can be set to 2400 bit/s. With the command
SYSTem:COMMunicate:SERial:BAUD? the current baudrate of an RS232 interface can be queried. Commands can be abbreviated to their upper case parts, for instance
SYST:COMM:SER:BAUD?.
Some instrument manufacturers, notably Agilent, Berkeley Nucleonics and
TektronixTektronix, Inc. is a North American company best known for its test and measurement equipment such as oscilloscopes, logic analyzers, and video and mobile test protocol equipment. As of November 2007, Tektronix is a subsidiary of Danaher Corporation....
, have implemented SCPI on many new general purpose instruments. Many smaller companies follow their lead. Typically their SCSI implementations roughly follow the spirit of the standard, but don't implement all finer details of the syntax, and don't follow the standard instrument classes commands in detail.
In 2002-2003, the SCPI Consortium voted to become part of the IVI Foundation (Interchangeable Virtual
Instruments).