A phase error in measurements made by a resistivity logging tool is estimated by positioning the tool above a conducting surface. Deviation of the measured phase difference between the transmitter and the receiver from 90° gives the phase error in the electronics. It is emphasized that this abstract is provided to comply with the rules requiring an abstract which will allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims.