... turn on meter after 8 minutes of non-use to conserve batteries, and will be locked automatically after ... 0-999ppm, with a resolution is 1 ppm, From 1000 to 9990 , the resolution is 10 ppm ,indicated by ... stabitized (30-45 seconds), press the hold button to save the reading.Attention1. Do not drop the ... the calibration level be as close as possible to sample to be tested. If you are testing higher p ...