First-order high-T/sub c/ single-layer gradiometers: Parasitic effective area compensation and system balance

We have previously reported an anti-parallel two-SQUID coupling scheme which can significantly improve the balance of first-order HTS single-layer gradiometers, and therefore improve the device performance in unshielded environments. We report on the behaviour of such devices fabricated on 10/spl times/10 mm/sup 2/ and 30/spl times/10 mm/sup 2/ STO bicrystal substrates. We present detailed studies of the balance of such devices, with particular emphasis on the time-dependent behaviour in unshielded environments, and with the device in motion.