We describe the design, fabrication, and performance of planar thin‐film dc SQUID’s and planar gradiometers in which a dc SQUID is incorporated as a null detector. Each gradiometer was fabricated on a planar substrate and measured an off‐diagonal component of changes in the magnetic field gradient. The gradiometer with the highest sensitivity had 127×33‐mm loops that could be connected in parallel or in series: The sensitivities were 2.1×10-13 and 3.7×10-13 T m-1 Hz-1/2, respectively. The intrinsic balance of the gradiometers was about 100 ppm for fields parallel to their plane, and a balance of about 1 ppm could be achieved for fields perpendicular to their plane. When the series‐loop gradiometer was rotated through 360° in the earth’s field, the output returned to its initial value to within an amount corresponding to a balance of 1 ppm. Possible improvements in sensitivity are discussed.
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机译：我们描述了平面薄膜直流SQUID和平面梯度计的设计，制造和性能，其中直流SQUID作为零检测器并入其中。每个梯度仪都在平面基板上制造，并测量了磁场梯度变化的非对角线分量。灵敏度最高的梯度仪具有127×33-mm的回路，可以并联或串联连接：灵敏度分别为2.1×10-13和3.7×10-13 T m-1 Hz-1 / 2。对于平行于其平面的场，梯度计的固有平衡约为100 ppm，而对于垂直于其平面的场，梯度仪的固有平衡约为1 ppm。当串联回路梯度仪在地球磁场中旋转360°时，输出返回到其初始值，其误差在1 ppm的余量内。讨论了灵敏度的可能提高。
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