Keypad force tolerances should not be considered in the same way as dimensional tolerances. Nearly all keypads are finger operated and the finger is relatively insensitive to exact loads. This is particularly true of single finger operation where loads of +/- 30% will not be noticed by a user. Examples include car switches, teletext terminals, car phones and instrument controls.
The exceptions are computer and typewriter keyboards where a tolerance of +/- 15% is required. In this case the finger rarely reaches full travel and operators are sensitive to forces because of the high frequency of use.
Capabilities depend upon membrane design and length of travel. Typical capabilities are outlined in this table.
Force variation is greatly affected by the fixing of the keypad base and by the escutcheon/keycap interface with the rubber. It is strongly recommended that early advice is sought.