To edit a database, click Menu on the iconbar icon of Units, roll off the arrow next to Edit and select one of the four databases.
Basically, the editor window is a logical extension of the browser window. As in the browser, you can restrict the display to units belonging to a certain system of measurement or a certain dimension. Also, the selection works just in the ge,me way, using the slider at the top left.
However, with this window, you can modify the database. You can change the full name and the symbol; this effectively deletes the old unit and defines a new one with the current settings.
You can assign a new system of measurement and a new dimension to the unit. The latter automatically fills in a new SI formula that gives the SI unit for this dimension. Normally, you just have to add a conversion factor to this formula.
Short info is just for your information; the entries are saved but not otherwise interpreted.
If all fields are filled in correctly, click on OK. The new information is then available in the database. To revert to the old data, click Discard. Closing the window or just selecting a different variable with the slider will also discard the changes.
To generate a new unit, click on New unit, fill in the details and click OK. Obviously, to delete the displayed unit, click the Delete button.
Mainly, assigning a dimension to a unit is just a method to organise the units. But additionally, you can assign a SI conversion formula to a dimension, i.e. the (compound) SI unit for that physical property. If you create a unit of that dimension in the Units Editor, this formula will automatically be filled in as SI conversion formula. You just have to complete this formula with the respective conversion factor. If you take care to quote the correct formula in the dimension editor and don't change the formula in the Units Editor apart from numerical factors, you ensure that your units database is ordered correctly.
Note that the SI formula must be build from SI base units; a list is given in the appendix.
If you want to create a unit entry for a unit whose dimension is not yet known, it is advisable to create such a dimension entry before.
If you delete a dimension, all units of that dimension are also deleted.
A system of measurement called SI base units is included with the database at delivery, and the proper SI base units can be found in the units database under this category. You can try to delete some of these units or add different ones, but this will only result in your confusion, as the SI base units that must be used to describe other units and that Units uses as target if you activate the To SI switch in the Conversion Window are as hard coded into Units as they are hard coded into the SI. It's therefore advisable either not to change the contents of SI base units or to delete this system altogether.
If you delete a system, all units of that system are also deleted.
On a typical pre-RiscPC machine, the databases will be saved into a folder "databases" inside of !Units. On a RiscPC and A7000, they are saved into a folder "Units" inside of the active Choices directory (typically $.!Boot.Choices.Units). On multi-user and network machines, this ensures that each user has access to his individual database.
Converting units |
Additional information
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