A field mill and a Gerdian type of conductivity apparatus are described which can replace two standard units on a slightly modified Kew Mk. II radiosonde. They are particularly suitable for an investigation of the electrical properties of the lower atmosphere, including clouds, in non-stormy conditions. Part of each device consists of a current-controlled inductor which varies the frequency of the sonde signal. The limitations and temperature effects are briefly discussed, and the results of a typical sounding given.