Formula for number of decimal digits

I’ve developed a scale calibration app that would ideally use decimal numbers. However since the length of decimal number varies by instrument I’ve have to resort to using a text field and then some rather complicated calculations to use the values in other formulas. It would be nice to be able to put a formula in “Decimal digits” . Additionally using a text field is annoying to mobile used, as they have to keep switching their keypad.
DecimalFeature