I declared a new float:

some_weight = fields.Float('Some Weight', digits_compute=dp.get_precision('Stock Weight'), default=0.0,

                           help="The some weight in g.")

Import the dp:

import openerp.addons.decimal_precision as dp

In Odoo Decimal Accuracy menu I have change the digits from 2 -> 4. All standard Odoo Foat Field that use dp of 'Stock Weight' are showing 4 digits of decimal. But not my new declared fields. How to make my new declare fields follow the dp of 'Stock Weight' without forcing the digits value in xml. Thank you.