9. When testing at low concentrations use the same tube for the blank and the
sample.
10. Always use the tube positioning ring. Always insert tube into the meter chamber
with the same amount of pressure and to the same depth.
11. Occasionally clean the chamber with a damp lint-free wipe, followed by an
alcohol dampened wipe. A clean chamber and tubes are essential for reliable
results.
68 CALIBRATION & ANALYSIS • CHLORINE