SCPI, the Language of Instruments

SCPI, or the Simple Command Protocol for Instruments, is a set of rules for communicating with instruments using simple, intuitive ASCII commands. For example, a PC connected to an HP 34401A Digital Multimeter (DMM) might say something like this:

PC:	IDN? [Identity?meaning, who are you?]
DMM:	HEWLETT-PACKARD,34401A,0,54-12-60"
PC:	MEAS:VOLT:DC? [Measure DC Voltage]
DMM:	+4.23789

This simple dialog is an example of SCPI. You can find more information on the SCPI protocol online at http://www.scpiconsortium.org. But don't worry; you don't have to learn the SCPI protocol. Many instruments have LabVIEW instrument drivers that allow you to control the instrument using high-level VIs, without having to know anything about the device's command-set or the SCPI protocol. You will learn more about instrument drivers shortly.

Not all instruments communicate using the SCPI protocol. Many serial and Ethernet instruments use protocols that are not as human readable because they are designed for efficiency. If you are unsure, read your instrument's programmer's manualmost have one, and if not, there will usually be a small section in the user manual describing the communication protocol and command set.