Replacing programmable instruments, keeping software compatibility in an automated test

When an instrument eventually goes obsolete or for any other reason a new instrument is put in place of one that is already a part of an automated test system, some programming work will follow to make the transition complete.  Even if the instruments are supposed to be software compatible, there are often minor details to tend.  The good news is that it is usually not that difficult or involved. Of course, exceptions can be noted but usually, it is not as big of a project as some anticipate.

We have had programmable test equipment with us now for well over fifty years and a lot has been written about making instruments easier to program. Indeed great progress has been made and hopefully, at some point in the future, and inclusive common language such as SCPI (Standard Commands for Programmable Instruments) for all test gear could be fully in place, functional, and accepted by all manufacturers.  This type of command structure may be more deterministic with some instruments than others, however at this point in time it seems to remain a fact that different programmable instruments evolved over different courses of development, in particular, temperature chambers, so I believe there will ultimately remain a few little details one should be prepared to attend to whenever swapping these instruments.

The following is an example of the methodology used to transition from communicating a Sigma temperature controller to Tidal Engineering’s Synergy line of temperature controllers used by TotalTemp Technologies. Outlined are the comparisons of the two different command strings and expected responses.

Without getting into software specifics such as conditional code and so on – This is how we make it work without a lot of difficulties.  (App note produced by Tidal Engineering (

Synergy Controller Application note 111

Please share your experiences with swapping instruments and compatibility between programmable instruments that perform the same function.

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