BS 90:1975
Current
The latest, up-to-date edition.
Specification for direct-acting electrical recording instruments and their accessories
Hardcopy , PDF
English
28-02-1975
Co-operating organizations
Foreword
Specification
1 Scope
2 Definitions
3 Classification
4 Permissible intrinsic errors and reference
conditions related to the measured quantity
5 Permissible intrinsic errors and reference
conditions related to time-keeping
6 Permissible intrinsic errors and reference
conditions for accessories
7 Permissible limits of variations
8 Permissible limits of variations for interchangeable
accessories
9 Electrical and mechanical requirements of
instruments and accessories
10 Constructional requirements for instruments and
their accessories
11 Markings and symbols for instruments and their
accessories
12 Categories of test
Appendices
A Concepts
B Friction effect of electrical measuring instruments
of the direct acting, continuous line recording type
Tables
1 Limits of intrinsic error of instruments related to
the measured quantity expressed as a percentage of
the fiducial value
2 Preconditioning of instruments
3 Reference conditions for the influence quantities
related to the measured quantity
4 Reference conditions for voltage, current and power
factor related to the measured quantity
5 Limits of intrinsic error related to the time
keeping expressed as a percentage of the true
elapsed time
6 Reference conditions for the influence quantities
related to time-keeping
7 Limits of intrinsic error of an accessory as a
percentage of the fiducial value
8 Normal values of the limits of the nominal range of
use and allowable variation as a percentage of the
measuring class index
9 Permissible limits of variation for a magnetic
induction of 0.5 mT
10 Variation due to mounting on a ferromagnetic panel
11 Normal values of the limits of the nominal range of
use related to time keeping
12 Relationship between the type of recording
instrument, the type of chart driving mechanism and
the accuracy class
13 Overload test of short duration
14 Current factor for overloads of short duration for
shunts
15 Value of test voltage
16 Examples of markings related to the reference
conditions and nominal ranges of use for instruments
and accessories
17 Symbols for marking instruments and accessories
18 Lower limit of effective range
19 Examples of limits of effective range and fiducial
values
Figures
1 Determination of maximum value of friction effect
2 Effective range 8 A to 50 A
3 Effective range 80 V to 110 V
4 Effect of temperature
5 Effect of temperature
6 Effect of frequency
7 Analysis of friction effect
8 Analysis of friction effect
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