H22PX & H22FX:
Simply remove the battery cap and battery. Between the two battery prongs there is a small black switch, slide the switch to the left for standard and to the right for metric.
1. Turn the unit on by sliding the switch towards the battery compartment and releasing.
2. Slide the switch towards the battery compartment and hold for 5 seconds.
3. The current units of measure will blink, release the switch.
4. Pull and release the switch to change between the settings (FT/F, M/C)
5. The unit will automatically exit the units of measure setting and return to the last mode (depth or temp) if the switch is not moved for 10 seconds.