Calibration & Analysis ∆ Calibration; Turbidity Standards; Tubes; Turbidity Calibration Procedure - LaMotte 2020t Manual

CALIBRATION & ANALYSIS
 CALIBRATION

Turbidity Standards

Only use AMCO or formazin standards with the 2020t/i. StablCal
should not be used to calibrate the 2020t/i .The diluent used in the StablCal
has a diff erent refractive index than traditional formazin standards and will aff ect the
results. The concentration of the calibration standard should be similar to the expected
concentrations of samples that will be tested. The standard should never be poured from
the tube back into the bottle. The standards will not have the same turbidity value in all
three modes.
The following standards are available from LaMotte Company:
Mode Units Nephelometric (N)
Meter
Code 1480
Code 1441
Code 1446
Code 1442
Code 1447
Code 1444
Standards may vary slightly from lot to lot for the ratiometric mode. Standard values for
the nephelometric mode and ratiometric mode are located on the standard bottle label.
Use the value on the turbidity standard bottle label as the target value when calibrating
the meter in the nephelometric mode and the ratiometric mode. Standards for calibration
in the attenuation mode should be prepared from Formazin.

Tubes

Use turbidity tubes (0260) that are free of scratches and imperfections in the light zone
between the bottom of the tube and the fi ll line. Discard scratched tubes. When reading
very low turbidity samples, do not use tubes or caps that have been used previously with
high turbidity samples. See page 38 for additional information.

Turbidity Calibration Procedure

The default calibration curve is nephelometric as indicated by (N) in the Menu bar. The
default units are NTU (2020t) and FNU (2020i). Other calibration curve options are
ratiometric and attenuation. The ratiometric calibration curve is indicated by (R) and the
attenuation calibration curve is indicated by (A). A user calibration should be performed for
each mode with standards that are appropriate for the meter and range.
For the most accurate results, a user calibration should be performed over the smallest
range possible. Use a calibration standard that, along with the blank, brackets the range
of the samples that will be tested. For example, if the samples that are to be tested are
expected to be below 1 NTU, more accurate results will be obtained by calibration with a
blank and a 1 NTU standard as opposed to a blank and a 10 NTU standard.
The number of measuring ranges for each mode varies.
Nephelometric (N)
2020t
0 NTU
1 NTU
-
10 NTU
-
- 100 FNU
Ratiometric (R)
2020i 2020t
0 FNU 0 NTRU
- 1 NTRU
1 FNU
- 10 NTRU
10 FNU
27
®
standards below 50 NTU
®
standards
Ratiometric (R)
2020i
0 FNRU
-
- 1 FNRU
- 10 FNRU
- 100 FNRU