LaMotte 2020i Turbidimeter - Manual (Page 29)

Testing Tips
1. Samples should be collected in a clean glass or polyethylene container.
2. Samples should be analyzed as soon as possible after collection.
3. Gently mix sample by inverting before taking a reading but avoid introducing air
bubbles.
4. For the most precise results, follow the recommended procedure for wiping a filled
tube before placing it in the meter chamber. Invert tube very slowly and gently
three times to mix the sample. Surround the tube with a clean, lint-free cloth. Press
the cloth around the tube. Rotate the tube in the cloth three times to assure that all
areas of the tube have been wiped.
5. Discard tubes that have significant scratches and imperfections in the light pass
zones. (Central zone between bottom and fill line).
6. When reading very low turbidity samples, do not use tubes or caps that have been
used previously with high turbidity samples.
7. Use the averaging option for low level measurements of turbidity.
8. The meter should be placed on a surface that is free from vibrations. Vibrations
can cause high readings.
9. Turbidity readings will be affected by electric fields around motors.
10. Carbon in the sample will absorb light and cause low readings.
11. Excessive color in a sample will absorb light and cause low readings. The user
should verify if a certain level of color will cause a significant error at the level of
turbidity being tested.
12. Observe shelf life recommendations for turbidity standards.
13. Do not use silicone oil on tubes when testing turbidity with the 2020.
14. When testing at low concentrations use the same tube for the blank and the
sample.
15. Always use the positioning ring. Always insert tube into the meter chamber with the
same amount of pressure and to the same depth.
16. Occasionally clean the chamber with a damp lint-free wipe, followed by an
alcohol dampened wipe. A clean chamber and tubes are essential for reliable
results.
17. For the greatest accuracy during the calibration procedure, be sure that after the
meter is blanked and the blank is scanned as a sample, the reading is 0.00. If
not, reblank the meter and scan the blank again until it reads 0.00. When
scanning the calibration standards as the sample, scan the calibration standard
three times removing the tube from the chamber after each scan. The readings
should be consistent. Use the last consistent reading to calibrate the meter. If the
readings are not consistent, avoid using an aberrant reading to calibrate the
meter.
ANALYSIS & CALIBRATION 29