A broad band correlation technique using anx‐yoscilloscope has been developed. When two noise signals are applied to the inputs of the oscilloscope, a characteristic pattern is formed on the oscilloscope face. It is shown that an equal intensity contour of the pattern, which may be obtained by photographing, is an ellipse and that the correlation depends only on the eccentricity and the angle of inclination of the ellipse. The bandwidth of this correlator is only limited by the oscilloscope. The instrument has been used to measure the correlation between fluctuations measured by two spatially separated probes in a plasma.