Hach-Lange 2100 N Laboratory Turbidimeter User Manual - Manual (Page 26)

Figure 6 Prepare filtered sample using membrane or glass-fiber
filter
1 Filter pump 4 Stopper 7 Filter
2 Hose 5 Filter holder
3 Filter flask 6 Tweezers
Turbidity measurement
W A R N I N G
Potential explosion and fire hazard. This instrument is for measuring water based
samples. Do not measure solvent or combustible based samples.
For accurate turbidity readings use clean sample cells and remove air
bubbles. Refer to
Clean the sample cell on page 17 and Remove air
bubbles from the sample on page 22.
Measurement notes
Proper measurement techniques are important in minimizing the effects
of instrument variation, stray light and air bubbles. For accurate and
repeatable measurements:
Instrument
• Make sure that the instrument is on a level, stationary surface that is
free of vibration during the measurement.
• The USEPA filter assembly is required for turbidity measurements
reported for United States Environmental Protection Agency (USEPA),
National Primary Drinking Water Regulations (NPDWR) or National
Pollutant Discharge Elimination System (NPDES) permits.
• Turn the instrument on 30 minutes (Ratio on) or 60 minutes (Ratio off)
before measurement. Keep the instrument on 24 hours a day if the
instrument is used regularly.
• Always close the sample compartment lid during measurement,
calibration and storage.
• Remove the sample cell from the instrument and turn off the
instrument if the instrument is stored for an extended time period
(more than a month).
• Keep the sample compartment lid closed to keep dust and dirt out.
Sample cells
• Always cap the sample cell to prevent spillage of the sample into the
instrument.
• Always use clean sample cells in good condition. Dirty, scratched or
damaged cells can result in readings that are not accurate.
• Make sure that cold samples do not “fog” the sample cell. Refer to
Prevent condensation on a sample cell on page 23.
• Store sample cells filled with distilled or deionized water and cap
tightly.
• For the best accuracy, use a single sample cell for every
measurement or a flow cell.
Note: As an alternative, matched sample cells may be used for measurements but
do not provide as good of accuracy or precision as a single indexed sample cell or
flow cell. When using matched sample cells, align the orientation mark on the
sample cell with the reference mark on the sample cell holder.
24 English