① Take out two colorimetric dishes from the attachment, clean the colorimetric dishes and measuring cups with distilled water or ultrapure water respectively, and wipe off any water stains and fingerprints on the outer wall with a lint free tissue or soft cloth. If it is not easy to clean, soak it in warm water with detergent for 30 minutes, and then rinse it clean with pure water.

② Connect the power to the instrument and turn on the power switch at the back of the instrument.

③ Instrument zeroing:

Pour distilled water or ultrapure water into a colorimetric dish (about 2/3 height); Clean the water stains and fingerprints on the outer wall with a lint free tissue or soft cloth, then place it in the measuring seat of the instrument and cover it with a light shielding cover.

Press the "Zero" button, and a wait prompt will appear: Set zero... Wait a moment.

Zero adjustment end display: NH3-N 0.0mg/L