Hach-Lange 2100 AN Laboratory Turbidimeter User Manual - Manual (Page 40)

Install a cell adapter
Note: Use the application specific calibration (ASC) ability of the instrument to
provide direct reading of results with cell adapters installed. If the ASC ability is not
used, a new calibration curve must be developed each time a cell adapter is used.
1. Align the tab on the cell adapter toward the front of the instrument
( Figure 9 ).
2. Put the cell adapter in the sample cell holder.
3. Calibrate the instrument each time the sample cell diameter is
changed. Calibrate using sample cells of the same path length as the
sample cell that will be used to measure samples.
Note: If test tubes are taller than the cover for the sample cell compartment,
use the tall light shield provided with the cell adapter.
Figure 9 Install a cell adapter
Remove a cell adapter
1. Carefully pull the cell adapter up until it is half out of the sample cell
holder.
2. Slowly turn the cell adapter 90 degrees counter-clockwise.
3. Pull the cell adapter up to remove it.
N O T I C E
Do not force the cell adapter out of the instrument as serious damage can
occur.
Using the optional filter assemblies
The USEPA filter assembly is used for turbidity measurements. The 455-
nm interference filter assembly is used for color measurements.
The 850-nm interference filter assembly can be used to make the
instrument meet ISO 7027 specifications.
Use the optional filter assemblies in
Accessories on page 54 as
necessary to select different wavelengths of light to measure samples.
Calibrate the instrument when the filter assembly is changed.
Application development using alternate wavelengths
It may not be possible to complete measurements in all units of measure
for a particular application using the optional filter assemblies (especially
turbidity measurements).
For example, the NTU unit of measure may not be the correct unit to use
at a 560-nm wavelength for a particular sample. But, the measurement
could be completed in Absorbance (ABS) or Transmittance (%T) modes.
The problem that will occur most often when using the turbidity units of
measure with the optional filter assemblies is that there will not be
sufficient light. Use cell adapters and smaller sample cells to provide a
shorter light path. Refer to
Use a cell adapter on page 37.
The correct selection of the measurement unit, wavelength and light path
length of the sample cell corrects many low-light conditions that occur
when applications are made using different wavelengths.
1. Prepare a series of standards solutions that agree with the range to
be measured.
2. Select the filter assembly that gives the correct wavelength and
install it in the instrument.
3. Select the correct unit of measure.
4. Measure the standards, and record the readings in a graph.
5. If a low-light condition occurs, do step 4 again using a cell adapter
and a smaller sample cell.
38 English