What is SCPI?
SCPI (Standard Commands for
P
rogrammable Instruments) is a standard
-
ized set of commands used to remotely
control programmable test and measure
-
ment instruments. The instrument firm
-
ware contains the SCPI. It defines the
syntax and semantics that the controller
must use to communicate with the instru
-
ment.
This chapter is an overview of SCPI and
shows how SCPI is used in Pendulum
Frequency Counters and Timer/Counters.
SCPI is based on IEEE-488.2 to which it
owes much of its structure and syntax.
SCPI can, however, be used with any of
the standard interfaces, such as GPIB
(=IEC625/IEEE-488), VXI and RS-232.
Reason for SCPI
For each instrument function, SCPI de-
fines a specific command set. The advan-
tage of SCPI is that programming an
instrument is only function dependent
and no longer instrument dependent. Sev
-
eral different types of instruments, for ex
-
ample an oscilloscope, a counter and a
multimeter, can carry out the same func
-
tion, such as frequency measurement. If
these instruments are SCPI compatible,
you can use the same commands to mea
-
sure the frequency on all three instru
-
ments, although there may be differences
in accuracy, resolution, speed, etc.
Compatibility
SCPI provides two types of compatibil
-
ity: Vertical and horizontal.
3-2 What is SCPI?
Introduction to SCPI
AC
AC
:INPut:COUPling AC
Figure 3-1
Vertical
This means that all instruments of the
same type have identical controls. For
example, oscilloscopes will have the
same controls for timebase, triggers and
voltage settings.
10E3
10.1234567890E3
10.1E3
:MEASure:FREQuency?
Figure 3-2
Horizontal
This means that instruments of different
types that perform the same functions
have the same commands. For exam
-
ple, a DMM, an oscilloscope, and a
counter can all measure frequency with
the same commands.
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