2201R Mobile Tester SCPI Reference Guide
Chapter 2 Remote control of the 2201R Mobile Tester
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Remote control applications and requirements
SCPI (pronounced ‘skippy’) is a world-wide standard. The basic idea of SCPI is to define a command language for
measurement systems that is independent of the related manufacturers.
Like most other measurement devices and instruments, the 2201R Mobile Tester can be integrated into test systems.
Operation can be automated through software with sequences of commands that set up the different instruments
and perform some measurements. The software can also evaluate the results and continue with another test. At the
end of the test sequences, an overall result or verdict is issued, along with the individual measurement results.
There is a variety of interfaces that can be used for remote control. The interfaces supported by the 2201R Mobile
Tester are USB, RS-232 and Ethernet (TCP/IP). The lack of a particular interface in the 2201R does not necessarily
mean that it cannot be integrated into the test system; computers integrated into remote control systems typically
support at least one of the interfaces that the 2201R Mobile Tester features.
What SCPI is
SCPI (Standard Commands for Programmable Instruments) was introduced in 1990. It is a world-wide standard,
independent of individual manufacturers.
The SCPI specification defines a command language for measurement systems and – in principle – is based on IEEE
488.2.
SCPI is independent of the physical transmission channel of the commands.
The idea behind SCPI is to shorten program development times for the automated control of test equipment and to
make that program development as efficient as possible.
Of course, one of the main requirements for this goal is that the language must be understood by as many
measurement devices as possible. Therefore, SCPI is promoted by the SCPI consortium. Quite a number of the main
test and measurement equipment manufacturers are members of the SCPI consortium.
Implementing just standard commands on a complex communications test system like the 2201R Mobile Tester
would lead to poor performance. Therefore, we are obliged to find a compromise between standard commands and
performance. This is the reason why you find many more SCPI commands in the 2201R Mobile Tester than specified
in the standard SCPI specification. However, all SCPI commands implemented in the 2201R Mobile Tester follow the
standard SCPI syntax and rules.
For additional details on the SCPI standard, the current version can be found on page
www.scpiconsortium.org/scpistandard.htm. You can download the full SCPI specification from there free of charge
(about 3.5 MB in PDF format).
SCPI command structure
SCPI defines programming commands, program messages, return values and data formats, which are consistent for
all measurement systems independent of their manufacturer and purpose.
SCPI uses a device-independent command set, the so-called “Common commands”, understood by all SCPI devices.
The 2201R-specific SCPI commands are called “Compound commands” and are only understood by the 2201R.
A subsystem in terms of SCPI is quite abstract: it is the set of commands implemented to perform specific tasks of
the SCPI device (the ‘measurement subsystem’ of the 2201R, for instance, is the set of commands implemented for
taking all kind of measurements, while the ‘configuration subsystem’ is the set of all configuration commands for all
areas of the 2201R).
All these subsystems use the same, SCPI-based messaging and data formats.
Any SCPI command is built in a hierarchical way — similar to how a path in a file system is built. The individual
command elements are separated by colons (:).
The complete set of commands of a subsystem is called the ‘command tree’.
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