Hach-Lange 2100 N Laboratory Turbidimeter User Manual - Manual (Page 34)

Advanced operation
Calibrate the turbidimeter with formazin standards
The instrument may be calibrated using prepared formazin standards
made from 4000-NTU formazin stock solution. Refer to
Accessories
on page 40.
Note: Use recently prepared formazin standards to get the accuracy specifications
for turbidity in
Specifications on page 5.
Prepare formazin standards
For the best accuracy and long-term data comparability, use formazin
stock solution from Hach to make formazin standards.
Note: As an alternative, a 4000-NTU formazin stock solution that is prepared by
the user may be used to make formazin standards. Refer to
Making 4000-NTU
formazin stock solution on page 35.
Prepare formazin standards immediately before calibration in an
environment that is at the same ambient temperature as the instrument.
Discard after use.
Refer to
Table 6 for the procedures to make the recommended
calibration standards.
Table 6 Formazin standard preparation
Standard Step 1 Step 2 Step 3
20 NTU Add 100 mL of dilution
water to a clean 200-
mL Class A volumetric
flask. Refer to
Prepare
dilution water
on page 21.
With a TenSette ®
Pipet, add 1.00 mL of
well-mixed 4000-
NTU formazin stock
solution to the 200-
mL flask.
Dilute to the mark
with dilution water.
Stopper and mix.
Table 6 Formazin standard preparation (continued)
Standard Step 1 Step 2 Step 3
200 NTU Add 50 mL of dilution
water to a clean 100-
mL class A volumetric
flask. With a TenSette 1
Pipet, add 5.00 mL of
well-mixed 4000-
NTU formazin stock
solution to the 100-
mL flask.
Dilute to the mark
with dilution water.
Stopper and mix.
1000 NTU Add 50 mL of dilution
water to a clean 100-
mL class A volumetric
flask.
With a TenSette 1
Pipet, add 25.00 mL
of well-mixed 4000-
NTU formazin stock
solution to the 100-
mL flask.
Dilute to the mark
with dilution water.
Stopper and mix.
4000 NTU Rinse a clean sample
cell two times with
well-mixed 4000-NTU
formazin stock
solution. Put about
30 mL of 4000-NTU
formazin stock
solution in the sample
cell. No dilution is
necessary.
— —
1 A class A volumetric pipet may be used in place of a TenSette Pipet.
Calibration notes
• Make sure that the instrument is in the same ambient conditions as
where it is used.
• Make sure that the standards are at the same ambient temperature as
the instrument before use.
• Use only the provided silicone oil. This silicone oil has the same
refractive index as the vial glass and masks minor glass differences
and scratches.
• Store the oiling cloth in a plastic storage bag to keep the cloth clean.
• If power is lost during calibration, the new calibration data is lost and
the last calibration data is used. To exit a calibration and not save the
new values, push UNITS/Exit.
32 English