A particular type of induction log designed to read an intermediate distance into the formation while maintaining good vertical resolution. The medium-induction array of eight coils (IM) is produced by three transmitters and five receivers running at 20 kHz. A small fourth transmitter coil was added in tools built since 1968. The midpoint of the integrated radial geometrical factor is 30 in. (76 cm) in radius. The vertical resolution is about 4 ft (1. 2 m) but varies with conditions. The IM is combined with a deep-induction log on the same sonde to produce a dual induction log.