"This standard applies to direct acting recording electrical measuring instruments for direct and alternating electrical quantities@ which are used for recording the varying values of one or more measured quantities as a function of time. It applies to strip@ drum and disk recording instruments@ viz: ?? ammeters; ?? voltmeters; ?? single-phase and polyphase wattmeters@ varmeters@ phasemeters and power-factor * meters (active or reactive); ?? frequency meters; ?? ohmmeters. It applies to multirange and multipurpose instruments of the above types. It applies to such instruments which incorporate rectifiers or diodes or thermocouples in their measuring circuits. It also applies to certain accessories used with such apparatus@ viz.: ?? shunts; ?? series resistors and impedances. Where other accessories are associated with instruments inasmuch as the calibration has been made of the instrument together with the accessory@ the standard is applicable to the combination of instrument and accessory. This standard also applies to electrically operated measuring equipment provided that the electrically operated measuring recording instrument (receiver) only is considered@ and that the relationship between the non-electrical quantity and the electrical one is known. It also applies to recording instruments@ together with their non-interchangeable accessories@ having electronic devices (other than rectifiers and diodes) as listed in Sub-clauses 1.3.1 to 1.3.3@ provided that they are marked with symbol(s) F-20 and/or F-21. It applies to recording instruments@ together with non-interchangeable accessories@ if any@ having neither an incorporated supply source nor needing an external supply source. Note. ?? The electronic devices of these instruments are energized by the same circuit as the measuring circuit and will sometimes be used for the protection of the measuring element. It applies to recording instruments@ together with non-interchangeable accessories@ if any@ having an incorporated supply source@ in general a battery@ provided that the electronic devices are used for influencing the recorded value only and that the voltage of the source@ and any voltage generated from that source@ does not exceed the limit of extra-low voltage. An external supply source is allowed when the nominal circuit voltage (circuit insulation voltage) of the measuring circuit does not exceed the limit of extra-low voltage. It applies to recording instruments@ together with non-interchangeable accessories@ if any@ in which the electronic device is solely used to supply an auxiliary voltage@ such as for ohmmeters@ provided that the voltage of the source does not exceed the limit of extra-low voltage. A voltage generated from that source may exceed the limit of extra-low voltage provided that the maximum current output at the measuring terminals is limited to 5 mA a.c. or 10 mA d.c. These instruments may have an incorporated supply source or may be fed by an external sour ce (see Subclause 1.3.2). Apart from the instruments listed in Sub-clause 1.3@ this standard does not apply generally to recording instruments having electronic devices other than rectifiers and diodes in the measuring circuit. This standard does not apply to: ?? recording instruments having a square-wave response greater than 90% on a square-wave with an amplitude equal to the effective range and a frequency of 5 Hz or higher; ?? integrating recording instruments; ?? indirect acting recording instruments; ?? recording instruments in which the measured quantity is presented in the form of digits@ codes@ punched cards@ etc.; ?? recording instruments in which the chart movement is a function of a quantity other than time. This standard does not contain requirements concerning the performance of recording instruments in relation to environmental conditions@ e.g. instruments intended to be: ?? weather proof; ?? flame proof; ?? shock proof; ?? vibration proof. * ""Power-factor""@ unless otherwise specified@ means ""active power-factor""."