# Positive and negative potential via two power supplies with common ground?

I need to use a positive and negative potential on a circuit including an instrumentation amplifier. My lab only has single supply power supplies (only offers positive voltage). I know that I can reverse the polarity and achieve a negative potential, but this means using multiple power supplies. (I am pretty sure that I cannot reverse the polarity on a single rail to fulfill both my negative and positive potential needs as this will cause a short). I do indeed need to tie the grounds for both supplies to one another, correct?

Because voltage is a difference, it means they do not have one terminal with no voltage and another one with positive voltage. You can call one 0V and another 5V, if you want. You can also call one -1382787V and the other one -1382782V, if you want. Or $\pi V$ and $(\pi+5)V$. Or -5V and 0V. Any two numbers $A$ and $B$ where $B-A = 5V$ will do.