USB Logic Analyzer Isolated Inputs?

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1

Hello,

I am wondering if the inputs on the TOL-15033 USB logic analyzer (https://www.sparkfun.com/products/15033) are isolated. Particularly if the ground for the system under test is separate from the ground of the analyzer. Basically I want to know if I can test a circuit that does not share a ground with the USB power supply that I use for the analyzer.

Thanks

2

Hi camsoup.

This logic analyzer has it’s ground connected to USB ground and is not isolated. You could achieve isolation if you used it in conjunction with something like [one of these though.](USB Isolator for Protection of all types of USB devices)

3

The more I think about it maybe I don’t need isolation. I would be interested in your thoughts. I am looking to connect a logic analyzer to look at the signals on an old 4 bit computer. It is using logic levels that are TTL compatible (around 4.6V for a high and about 0.2V for a low). It has its own power supply that connects to the AC mains (plug is just a two prong without an earth ground). Would this be okay to use the logic analyzer on? Ie should I expect any issues interconnecting (through the analyzer) the ground for the logic analyzer and the ground for the system under test?

4

I think you’re probably OK without an isolated logic analyzer in your case.

Just make sure the ground for the analyzer is connected to the ground on your device and plug the devices power cord into the same outlet/power strip as the computer you have the logic analyzer plugged into and you should be fine.