1.1 This standard concerns single-channel and multi-channel electrocardiographs with analogue circuits which linearly amplify and display cardiac potential signals at the body surface, with respect to time. 1.2 This standard does not apply to non-linear systems such as digital electrocardiographs, vectrocardiographs, heart monitors, information-processing portions of electrocardiographs and other associated special-purpose instruments. Instruments with internal signal storage with non-linear processing are also outside the scope of this standard. 1.3 This standard is intended for the use of metrological services and other responsible governmental agencies. It specifies the metrological characteristics to be determined, methods and equipment for testing and initial and subsequent verifications of electrocardiographs that are regulated by laws. Metrological characteristics include errors in measuring voltage signal and time intervals among other characteristics that affect measurement accuracy. Procedures are given for determining the relative error of measurement of sixteen instrument characteristics. These testing and control procedures provide a basis for ensuring that electrocardiographs of adequate accuracy are available for clinical measurements. 1.4 This standard does not address pattern approval, terminology, technical requirements, electrical safety and the associated test methods.