In my organization, we often use four-channel oscilloscopes to check out products. Each probe reference might be several hundred volts away from the others, which makes using standard scopes problematic. As best I can tell, there are only a few 'scopes on the market with the required level of channel-to-channel isolation, all from Tektronix, all costing at least $4,000. I would like to reduce this cost.
Another option would be to use differential voltage probes with a cheaper scope, but those are also very expensive, and we run the risk of someone forgetting and connecting a non-differential probe to the cheaper scope and blowing it up.
A third possibility would be to build my own isolators or differential mode probes for use with a cheaper scope. But I suspect that gets complex very fast, especially when one does not typically build such precise things.
A fourth possibility would be to use several PC-based USB oscilloscopes, each connected to a USB isolator. But I've never seen a system that allows multiple USB scopes in the same software, and I suspect there would be serious synchronization issues.
I have very low bandwidth, sample rate, and accuracy requirements; this is part of a test stand for a 360 Hz inverter, so if I can see an 20 mS window with 10 uS granularity, a 600 VAC RMS sine wave with 10V granularity, and a 5V feedback pulse with 100 mV granularity, I'm done.
What is the cheapest way to achieve my goals reliably?