Remote controlling instruments using LXI

440px-LXI_Logo.svgA lot of modern lab equipment like power supplies, oscilloscopes, signal generators and many more, have an onboard Ethernet interface and an “LXI” logo. LXI stands for “LAN eXtensions for instruments” and replaces the old GPIB IEEE-488 parallel control bus. You can use this interface to control your instruments remotely from a PC. With LXI Class-A and Class-B devices you can even exchange trigger data over the network. But let’s stick today with the simplest version: Class-C devices. These interfaces provide only remote control features.  The good thing about Class-C: you will find this type even in hobbyist instruments. For example, even the mid-range Rigol instruments today have an LXI interface.

Often the manufacturers provide remote control software (usually only for Windows PCs), sometimes plugins for LabView. The quality of this software is sometimes ok, but often not very good.

However as LXI is an open standard, you don’t need the software of the device manufacturer. You can simply create your own. And if you’re usually working on the command line on Linux or MacOS, it is really simple to use it.

The LXI command protocol is a simple text protocol over a TCP connection. That means you can even use the simple “telnet” command to control your instruments remotely.

Let’s do an example with the DSA815. First, download the Programming Guide from Rigol. Unfortunately this one comes in CHM format which is used in Windows. We need an additional program to read it on other operating systems. On MacOS iChm does the job.

Now, connect to the instrument using the telnet command line tool. The port on Rigol instruments is 5555, which is easy to remember. With other vendors the port might be different, check your manuals.

$ telnet 5555
Connected to
Escape character is '^]'.
Rigol Technologies,DSA815,DSA8A154402661,

Seems to work. The “*IDN?” command is a standard command that is implemented by all LXI instruments and returns the ID of the instrument.

Do you want more? Ok,  lets do a frequency response plot from 100 kHz to 10 MHz using the internal tracking generator.

# enable tracking generator output
# average 1000 measurements
# frequency range from 0 to 10 MHz
:SENSe:FREQ:STOP 10000000

You can do similar things with oscilloscopes, multimeters and function generators. This allows very powerful automated measurements as you can control different instruments from a central console. Note that while the protocol is standardized, the commands are not. Therefore you have to check the manual from your vendor.

You want to do even cooler things? Have a look at this article from Ken Shirriff. I will also show how to to jitter measurements down to 1ns with a mid-range Rigol scope.

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