Working with the Renard series of preferred numbers specified in ISO 3.
Project description
The Renard series are a system of preferred numbers used in engineering applications which specifies a geometric sequence of numbers over the range one to ten. The numbers are selected to be convenient to use an to minimise the maximum relative error when an arbitrary number is replaced by the nearest Renard number. The series were proposed by the French army engineer Colonel Charles Renard and subsequently standardised in ISO 3-1973.
For example, the R5 series contains six values (1.00, 1.60, 2.50, 4.00, 6.00) which cover a one-order of magnitude range of values (one decade) from one to ten. These base values repeat again to cover the next decade from 10 to 100, as 10, 16, 25, 40, and 60.
This renard library is useful for selecting values from the least rounded R5, R10, R20, R40 and R80 decades, the medium rounded R’10, R’20 and R’40 decades, and the most rounded R”5, R”10 and R”20 decades.
Status
Installation
The renard package is available on the Python Package Index (PyPI):
The package support Python 3 only. To install:
$ pip install renard
Python Interface
For full help:
>>> import renard >>> help(renard)
In the meantime, here are some highlights.
To find the nearest E24 value to 319 use:
>>> from renard import find_nearest, R20 >>> find_nearest(R20, 319) >>> 315.0
To find the next value greater-than or equal-to 184 in the E96 series use:
>>> from renard import find_greater_than_or_equal, R80 >>> find_greater_than_or_equal(R80, 182) >>> 185.0
To find a few values around the specified value, use:
>>> from renard import find_nearest_few, R20 >>> find_nearest_few(R20, 5000) >>> (4500.0, 5000.0, 5600.0)
Command-Line Interface
There’s also a handy command-line interface. Run eseries --help to see a list of commands:
$ renard --help renard Usage: renard [options] <command> [<args> ...] Options: -h --help Show this screen. -v --verbose Use verbose logging Available commands: ge gt help le lt nearby nearest range series tolerance See 'renard help <command>' for help on specific commands.
To find a nearby value, use:
$ renard nearest R20 37726 35.5e3
If you prefer an SI exponent symbol, supply --symbol or -s:
$ renard nearest R20 37726 -s 35.5 k
To show values around the given value, use the nearby command:
$ renard nearby R40 52e6 -s 50 M 53 M 56 M
To show the smallest value greater than or equal to the given value, use the ge command:
$ renard ge R40 52e3 -s 53 k
To show all values in an inclusive range, use the range command:
$ renard range R5 74e-9 34e-6 -s 100 n 160 n 250 n 400 n 630 n 1 µ 1.6 µ 2.5 µ 4 µ 6.3 µ 10 µ 16 µ 25 µ
Project details
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