1.1 This standard applies to direct-acting recording electrical measuring instruments used for recording changing values of one or more measured quantities as a function of time. The standard applies to continuous paper-feed writers, drum writers and dis writers of the following types:
——ammeters;
——voltmeters;
——single-phase and multi-phase wattmeters, varmeters, phase difference meters, cos -meters and sin ((r-meters;
——frequency meters;
——phmmeters. The standard applies to instruments of the above types with more than one measuring range and more than one function. The standard applies for instruments with rectifiers or diodes and for instruments with thermocouples in their measuring chain(s). It also applies to certain accessories used with such instruments, such as:
——shunts;
——series resis ors and impedances the standard only applies to the combination of instruments and accessories insofar as the instrument has been calibrated together with the accessories. 1.2 The standard also applies to electrically operating measuring instruments as far as it concerns only the recording electrically operating measuring instrument (receiver) and the relationship between them. the non-electrical quantity and the electrical quantity are known. 1.3 The standard also applies to recording instruments, together with their non-interchangeable accessories, equipped with electronic components (other than rectifiers and diodes) as indicated in 1.3.1 to 1.3.3. , provided they bear the symbols F-20 and/or F-21. 1.3.1 It applies to recording instruments, together with any non-interchangeable accessories, which do not have a built-in power source or require an external power source. Note The electronic components of these instruments are powered by the same circuit as the measuring chain and are sometimes used to protect the measuring element. 1.3.2. It applies to recording instruments, together with any non-interchangeable accessories, which have a built-in power source, usually a battery, provided that the electronic components are used only to influence the recorded value and that the voltage of the power source and any voltage generated by this current source does not exceed the maximum for a very low voltage.
NEN 3556-1985 history
1985NEN 3556-1985 Direct acting recording electrical measuring instruments and accessories