We have fabricated a first-order, directly coupled gradiometer with a gradiometric balance below 0.1% without balance adjustment by selecting the coupling direction of the pickup coil and the superconducting quantum interference device. The noise of the gradiometers with various balances measured in an unshielded environment decreased in proportion to the improvement in balance. However, the noise of the gradiometer with a balance of 0.03% was limited by the gradient field component of the environmental noise. Magnetocardiogram measurement with this gradiometer in an unshielded environment was also demonstrated.
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