Furman polarity?

Well, BALANCED is 60 volt hot and 60 volt neutral.
So the actual result would be 120 between the two, or 60 hot to ground, and 60 volts neutral to ground.
If you are using some inexpensive 'checker' it make just not work on balanced outlets.
ALL USA "BALANCED" power is 60 volts/60 volts.

The issues of balanced power are complicated enough that it is illegal to have it in the walls of a residence per codes.
In industrial uses, it has to be clearly marked as balanced on every outlet.

Both of my power conditioners are outputting balanced A/C.

As does my isolation transformer...used only for low current or digital gear.
It is a 400va transformer.

Interesting question, I use a P-2400 IT, but have never made any attempt at comparing it's output to input. I would have assumed that an isolation transformer effectively removes any relationship between the AC input hot/neutral and the transformer output. I guess one could measure the AC phase of the output and match it to the input, but that would seem to be an arbitrary relationship anyway.

..and I'd actually expect that most simply line testers would at least show some kind of neutral/earth fault when measuring balanced AC output.

I agree with Rayooo. I have been running balanced isolation transformers for almost 8 years now. Those little AC outlet testers will not work properly with balanced power because the two 60V poles are the same (i.e., neither "hot" nor "neutral"). Plug-in testers are meant to work on standard circuits, where the neutral is grounded.

Polarity on standard household circuits is important because devices like lamps often have the neutral tied to the metal structure. If power at the outlet is reversed, that would make metal parts of the lamp HOT with respect to ground, and present an electrocution hazard. Therefore you want to make sure poles are not reversed. Also, in devices where the power switch in on the HOT side, when polarity is reversed, the neutral side inside the device will be live, even when the power swicth is in the off position.

Balanced power presents the same risks, however, the use of lighting equipment on balanced power is prohibited. Balanced power equipment also usually comes with GFCIs to help prevent protection from shock. There is no need to use circuit analyzers on balanced power equipment.

Edit: This forum needs post editing capability. Sentence two of the last paragraph should read "Balanced power equipment also usually comes with GFCIs to PROVIDE protection from shock".

Thank you all for your responses. My understanding of balanced power was incorrect.