The plasma sensitivity to magnetic field error effects has been tested experimentally using externally introduced global field errors in the ELMO Bumpy Torus (EBT). A critical field (delta B/sub r//B)/sub cr/ approximately 0.6-1 x 10/sup -3/ was observed, below which the plasma is essentially free from convective cells, toroidal currents, and instabilities. The observed critical value is comparable to a neoclassical critical field error (delta B/sub r//B)/sub cr/ approximately equal to rho/R, the ratio of the ion Larmor radius to the major radius of the torus.