LaMotte 2020wi Portable Turbidity Meters - Manual (Page 36)

CALIBRATION & ANALYSIS
 CALIBRATION
Turbidity Standards
Only use AMCO or formazin standards with the 2020we/wi. StablCal ®
standards below 50 NTU should not be used to calibrate the 2020we/wi.
The diluent used in the StablCal ® standards has a different refractive
index than traditional formazin standards and will affect the results.
The concentration of the calibration standard should be similar to the
expected concentration of sample that will be tested. The following
standards are available from LaMotte Company:
1480 0 NTU/FNU Standard, 60 mL (EPA or ISO)
1450 1 NTU Standard, 60 mL (EPA)
1453 1 FNU Standard, 60 mL (ISO)
1451 10 NTU Standard, 60 mL (EPA)
1454 10 FNU Standard, 60 mL (ISO)
1452 100 NTU Standard, 60 mL (EPA)
1455 100 FNU Standard, 60 mL (ISO)
Turbidity Calibration Procedure
The default units are NTU and FNU and the default calibration curve
is formazin as indicated by (F) in the Menu bar. A 2020we, which uses
NTU, will be used in the following examples. For the most accurate
results, a user calibration should be performed. The Japan Standard
calibration mode, as indicated by (J) in the Menu bar, should be used
only with Japanese Polystyrene Standards (0-100 NTU). To change the
settings see the Set Up Instructions on page 9.
For the most accurate results, perform a calibration 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 100 NTU standard.
The meter has fi ve measuring ranges:
0 – 11 NTU/FTU
11 – 110 NTU/FTU
110-300 NTU/FTU
300-600 NTU/FTU
600-4000 NTU/FTU
Each range can be calibrated with one point per range. (Six points
total - a blank plus one point in each of the fi ve ranges - if each range
is calibrated.) New calibration points will replace old calibration points
independently for each range. If one range is recalibrated, the meter will
36
Calibration