Hold Function : saves measurements for convenient reading and recording.
Auto-off function : the meter shuts off automatically after 10 minutes of non-use to conserve batteries.
Measurement Range : 0-9990 ppm. From 0-999 ppm, the resolution is in increments of 1ppm. From 1000 to 9990 ppm, the resolution is in increments of 10ppm, indicated by a blinking 'x10' image.