BS 89-1:1990 download.Direct acting indicating analogue electrical measuring instruments and their accessories — Part 1: Specification for definitions and general requirements common to all Parts.
1.1 BS 89-1 applies to direct acting indicating electrical measuring instruments having an analogue display, such as:
— ammeters and voltmeters;
— wattmeters and varmeters;
— frequency meters of pointer and vibrating-reed types;
— phasemeters, power-factor meters and synchroscopes;
— ohmmeters, impedance meters and conductance meters;
— multi-function instruments of the above types.
1.2 It also applies to certain accessories used with these instruments, such as:
— shunts;
— series resistors and impedance elements.
If other accessories are associated with instruments, BS 89-1 is applicable to the combination of the instrument and the accessory provided that the adjustments have been made for the combination.
1.3 BS 89-1 also applies to a direct acting indicating electrical measuring instrument whose scale marks do not correspond directly to its electrical input quantity, provided that the relationship between them is known.
1.4 BS 89-1 also applies to instruments and accessories having electronic devices in their measuring andlor auxiliary circuits.
1.5 BS 89-1 does not apply to special purpose instruments which are covered by their own IEC
the mechanism by means of which the instrument may be adjusted so that the mechanical zero coincides with the appropriate scale mark
2.3.11.2
mechanical span adjuster
the mechanism by means of which the instrument may be adjusted so that the lower/upper limit of the measuring range coincides with the appropriate scale mark
2.3.12 Electrical zero
The equilibrium position which the index will approach when the measured electrical quantity is either zero or a set value and the control circuit (if any), producing a restoring torque, is energized.
2.3. 12. 1
electrical zero adjuster
for an instrument which needs an auxiliary supply, the mechanism by means of which the instrument may be adjusted so that the electrical zero coincides with the appropriate scale mark
2.3.12.2
electrical span adjuster
for an instrument which needs an auxiliary supply, the mechanism by means of which the instrument may be adjusted so that the lower/upper limit of the measuring range coincides with the appropriate scale mark
2.4 Characteristic features of instruments
4 Reference conditions and intrinsic errors
4.1 Reference conditions
4.1.1 The reference values of the influence quantities shall be as given in Table I-i.
4.1.2 The reference value for the ambient temperature shall be selected from 20 °C, 23 °C or 27 CC which are in accordance with IEC Publication 160: Standard Atmospheric Conditions for Test Purposes.
4.1.3 Reference conditions different from those given in Table 1.1 may be specified, but they shall then be marked in accordance with Clause 8.
4.2 Limits of intrinsic error, fiducial value
When the instrument together with its non-interchangeable accessory(ies) (if any) or accessory is under the reference condition given in Table I-i and is used between the limits of its measuring range and in accordance with the manufacturer’s instructions, the intrinsic error, expressed as a percentage of the fiducial value, shall not exceed the limits appropriate to its accuracy class. Values stated in a table of corrections supplied with the instrument or accessory shall not be taken into account in determining the errors.
NOTE I The intrinsic error includes other errors such as those due to friction, amplifier drift. etc.
NOTE 2 The accuracy classes relating to each type of instrument or accessory are given in the appropriate parts (Clause 3).
4.2.1 Correspondence between intrinsic error and accuracy class
The maximum permissible error is related to the accuracy class such that the class index is used as the limit of error, expressed as a percentage with positive and negative signs.
NOTE For example. for a class index of 0.05. the limits of intrinsic error are ± 0.05 % of the fiducial value.
5.3.1 If preconditioning is specified for the determination of variations, the manufacturer shall state the preconditioning period and the value(s) of the measured quantity(ies) and of the auxiliary supply, if any. The preconditioning period shall not exceed 30 mm.
5.3.2 The variations shall be determined for each influence quantity separately.
During each test all influence quantities shall be maintained at their reference conditions except for the influence quantity for which the variation shall be determined.
5.3.2.1 When an influence quantity has a reference value, the influence quantity shall be varied between that value and any value within the limits of the nominal range of use as given in Table 11-1, unless otherwise marked.
5.3.2.2 When an influence quantity has a reference range, the influence quantity shall be varied from each limit of the reference range to the adjacent limit of the nominal range of use.
6 Further electrical and mechanical requirements
6.1 Voltage tests, insulation tests and other safety requirements
The requirements for the voltage tests, insulation resistance tests and constructional requirements
relating to safety are included in IEC Publication 414: Safety Requirements for Indicating and Recording
Electrical Measuring Instruments and their Accessories.
For additional requirements relating to electronic devices of instruments and/or accessories,
IEC Publication 348: Safety Requirements for Electronic Measuring Apparatus, shall be applied.
9.1 Requirements for markings
9.1.1 The marking shall be applied on or adjacent to the relevant terminal.
9.1.2 If there is insufficient space adjacent to a terminal for the marking specified, a permanently attached nameplate shall be provided having details of the terminals and identifying them in an unambiguous way.
9.1.3 The markings shall be and remain legible and indelible and of a colour which contrasts with the background or shall he moulded.
9.1.4 A marking shall not be applied to a removable part of a terminal (such as a terminal head).
9.1.5 If markings are applied to a cover over several terminals, it shall not be possible to fit the cover so that the markings become incorrect.
9.1.6 When a diagram of connections is supplied, the marking for a terminal shall be identical to that on the diagram of connections relating to that terminal.
9.2 Earthing (grounding) terminals
9.2.1 Terminals which are required to be connected to a protective earth (ground) for reasons of safety shall be marked with symbol F-43 (Table 111-1).
9.2.2 Terminals which are required to be connected to a noiseless earth (ground) to prevent impairment of performance shall be marked with symbol F-44 (Table Ill-i).
9.2.3 Terminals which are connected to accessible conductive material but which are not necessarily required to be connected to earth (ground) shall be marked with symbol F-42 (Table lIT-i).
9.3 Measuring circuit terminals
10 Tests to prove compliance with this standard
10.1 The Performance of instruments and accessories specified in this standard may be established using
the tests given in Part 9 and these tests may be supplemented by tests given in other relevant IEC
standards.
10.2 Tests under two categories are required: type tests and routine tests.
10.2.1 Type tests shall be made on a single specimen of each design or on a small number of specimens.
10.2.2 Routine tests shall be made on all items.
10.3 In general, BS 89-1 does not state which tests are type tests and which are routine tests.
NOTE 1 Some routine tests are given in Appendix Al.
NOTE 2 Routine tests are usually sufficient when made periodically during the life of an instrument or an accessory to ensure continued accurate performance and are normally used for recalibration.