Is it possible to subtract two waveforms without a common reference or ground?

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Subtracting two waveforms without a common reference or ground is challenging but can be approached by considering the potential difference between each waveform and their respective battery negative terminals. The assumption that the negative terminals are equal allows for the arithmetic subtraction of the two stand-alone quantities, A and B, at the receiving end. However, this method may introduce errors due to potential differences between the battery grounds. It is crucial to ensure that the wireless sensors accurately transmit the amplitudes of A and B. Ultimately, while it is theoretically possible to perform the subtraction, careful consideration of the grounding and potential differences is necessary for accurate results.
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Morning :)
I am trying to sample two different waveforms, and subtract the one from the other. Basically, I have A, B, and want C=A-B.
The device calculating the C=A-B is remote, connected to the two sampling A and B via a wireless link.
A and B do not have any common reference or ground, and the devices sampling them are battery operated.
Can I simply take the potential difference between A and a battery's negative terminal... and B and the next battery's negative terminal... and assume that the negative terminals are equal, such that I now have two waves that I can subtract from each other to get a proper difference between the two?
 
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It sounds like each floating wireless sensor is sending the amplitude of A and the amplitude of B. As such, they are stand-alone quantities, without any reference anymore. So yes, just do a simple arithmetic subtraction at the receiving end of the wireless link.
 

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